ESE's works engine tuner

[andreas]

Last plated cylinder I ported was chrome, I did the exhaust and all possible ports where the ring passes, there was no flaking, after alot of runtime that is
. Is niqasil more fragile?

[katinas]

Wob , I have doubts about NdFeB magnets on a one peace fully machined 75 mm rotors with 60mm stators. From what I had in my hands, magnets are definitely weaker than on rotors used for the first CRF EFI engines .
I think Denso started to use neodymium with EFI engines, for Honda from 2009 and (sadly for us) rotors are bigger 90mm and from 2017 even bigger 102 mm.
I could not found small 75 mm rotor with magnets as strong as on latest bigger rotors for EFI. Honda RS 250 NF 5 rotor magnets are slightly stronger than CR but weaker than EFI and RS 250 stator diameter is 57 mm .

Stators for CR125/250 engines 2002-2007 goes with two types
8 poles 12v- CR 250 2002-2007 and 2004 CR 125 all with TPI sensors ( only two wires from stator directly to small regulator/rectifier and then it is possible to adapt what we want even DC-CDI-P4 for three or four cylinders) With two original CR 125 2004 CDI it works really good on V 90 2 cylinders engine

4 poles only on CR125 2002-2003 and 2005-2007 with TPI sensor ( stator with three wires and 2 different circuit, one for charging, other low voltage for timing chip and all wires connected directly to CDI not to regulator/rectifier ) With two original CDI on V 90 2 cylinders engine work only at idle rpm. Maybe it work with 180 degrees 2 cylinders, but I did not tested.

[_____]

Honda stuck with short ( 104,105 ) rods for years , but the last champ winning 250 had a longer ( 109 ) rod.
The Denso ignitions starting from around 2000 are all the same basic hardware - 60mm stator and 12V output , and 1-5 taper.
There was a change to a one piece fully machined rotor , and this also has NdFeB magnets.
A 4 coil stator with these magnets makes the same power as an 8 coil with the older Ferrite magnets.
And that 8 coil stator with the good magnets will produce over 4A , enough for a DCCDI P2 running both CDI .

So would this stator be the right one to choose?
https://www.ebay.de/itm/CRF450R-31100-MEB-670-Magneto-Generator-Stator-Coil-for-Honda-31100-MEB-671/173739551192
Judging from the bolt pattern it looks like a copy of the Denso type. And that particular one has only two wires coming out of the stator - think I will buy one and test it.

Thank you katinas, I bought myself a CRF 250R Rotor and will start playing with that :-)

Also the Hidira rotor/Stator of the KTM 65SX looks a lot alike the denso type (bolt pattern wise)

Cheers
Chris

[katinas]

Chris, on CRF 250/450 carb models engines, with 60 mm stator, they used another, say, third type
8 poles, with two wires connected directly to CDI unit, not to regulator/rectifier. Similar to CR 125 2000-2001 CR 250 1999-2001, but this stators generated high voltage to CDI. So there is some doubts. Maybe there is some type of regulator inside CRF CDI, but I dont know

CR 250 2002-2007 and CR 125 2004 12v stators with rectifier could be compatible with your CRF 250 rotor and DC-CDI, or aftermarket 8 pole stators with windings for lightning.

[41juergen]

Thank's a lot for the feedback Wob. Have done a set of RGV250 barrels and they go into the engine soon.

Just one other question: I'm looking for a 115mm conrod with the following dimensions:
small end: diameter 21 mm, width min 16 mm
big end: diameter 31mm, width min 16mm
At least prox don't have an appropirate one, even with a wider width of the small or big end...

[Michael Moore]

http://hotrodsproducts.com/ProductSearch.aspx

You can put in a conrod length (and +/- amount) and it will serve up all that are found, but then you have to look at each one to determine the BE/SE diameters, pin sizes, etc.

cheers,
Michael

[katinas]

https://www.royalrods.com.tw/yamaha-outboard/RY-2107.html 116x21x32
They are very informative
And Yamaha RD 400 115mm but big and small ends maybe not as big as you need

Very interesting to follow how manufactures testing with conrod lenght on MX 125 through years
Honda CR 125 100 104 mm
Yamaha YZ 125 105 102 mm
Kawasaki KX 125 106 109 104 mm
Suzuki RM 125 105 102 110 mm
KTM SX 125 110 mm

Assumed with road racing reed engines rod dimensions, looks like for reed valve 125, for good balance, 110 mm rod is maximum.

Remember street Jawa 350, 2 cylinder engine with relatively very long rods - 145 mm, with 65 mm stroke and 58 mm bore.

[TZ350]

RD 400 115mm but big and small ends maybe not as big as you need

An RD400 rod is what I use. I have been spinning mine to 14,000 rpm. 48mm stroke, original 115mm Yamaha Mitaka 2T2 rod with an RGV250 flat caged B/E brg.

342930

[Michael Moore]

The 2T MX bikes are pretty standardized at 125mm OC, but if you go back to the 99 KTM 250SX with 67.5x69.5 instead of the modern 66.5x72 numbers you can get a 132mm rod.

I find it interesting that if roughly square B&S seems to be ideal (at least that is what I've gathered from comments) then KTM and Yamaha should have stayed with those dimensions as used in their prior to 2000 MX 250s. But the undersquare dimensions seem to have been standard for 20 years now. I presume there's a reason why, perhaps they are a bit more responsive for dirt use compared to RR hp from square dimensions?

cheers,
Michael

[katinas]

https://www.tkart.it/en/magazine/under-review/screamer-iii-shifter-iame/#2
Some photos with cylinder head.
https://www.tkart.it/en/magazine/under-review/iame-ok-and-okj-a-lot-of-changes/#2

I took this pictures today at a tool store, nothing special, four transfers piston ported ECHO chainsaw 50 cc max 12500 rpm 3.5 hp
engine, but one interesting thing. B windows arranged upward, like as usual C.


http://www.arcticinsider.com/Article/Everything-You-Wanted-to-know-about-the-Arctic-Cat-C-TEC2-8000-Engine A transfer windows shape, add photo.

[mantonakakis]

Thanks Husa, I'd just started looking for 'Farmaken'. I'll keep it in mind.

This might be my first post on this site, but I have been reading this thread for a few years now, and I am almost caught up!
Thanks again to Husa, as I am hoping to build or procure an ATAC valve soon too for a current project. Some moped guys have used this valve with some success, I think:
https://www.matco-norca.com/product.cfm/Brass-Gate-Valves/730-Bronze-Quick-Opening-Gate-Valve/product_id/61
It seems like it could be shortened, and it should be possible to braze it to the header.
And thank you to everyone else (Frits, Wobbly, TZ, everyone!) for all of the knowledge (often learned the hard way) shared here.

[Lightbulb]

Turbo charges or super charges have been banned already in most of the model engine classes these days. They also introduce limits for plenum volumes under the venturi point to the valve as well.
Some great drawings that were shown. It is great to see what people have done quite a few years ago.
Neil

[husaberg]

The 2T MX bikes are pretty standardized at 125mm OC, but if you go back to the 99 KTM 250SX with 67.5x69.5 instead of the modern 66.5x72 numbers you can get a 132mm rod.

I find it interesting that if roughly square B&S seems to be ideal (at least that is what I've gathered from comments) then KTM and Yamaha should have stayed with those dimensions as used in their prior to 2000 MX 250s. But the undersquare dimensions seem to have been standard for 20 years now. I presume there's a reason why, perhaps they are a bit more responsive for dirt use compared to RR hp from square dimensions?

cheers,
Michael

My musing is the square is the best comromise for a high revving and highest possible output two stroke
Undersqaure is the best compromise best for a mildly tuned MX 250.
The rod length is also likely a design compromise to keep the height down and or give a bettr ring life as the ring pack can be lower for a given height.

https://www.royalrods.com.tw/yamaha-outboard/RY-2107.html 116x21x32
They are very informative
And Yamaha RD 400 115mm but big and small ends maybe not as big as you need

Very interesting to follow how manufactures testing with conrod lenght on MX 125 through years
Honda CR 125 100 104 m[m
Yamaha YZ 125 105 102 mm
Kawasaki KX 125 106 109 104 mm
Suzuki RM 125 105 102 110 mm
KTM SX 125 110 mm

Assumed with road racing reed engines rod dimensions, looks like for reed valve 125, for good balance, 110 mm rod is maximum.

Remember street Jawa 350, 2 cylinder engine with relatively very long rods - 145 mm, with 65 mm stroke and 58 mm bore.

KTM200 has a nice long rod in 22mm crankpin
118mm


03.6248 ProX Con.Rod Kit KTM200SX-EXC ’98-16 20.00 28.00 118.00 15.90 15.90 151.40 94.00 22.00 55.00 22 x 37 x 1.0

[lohring]

Turbo charges or super charges have been banned already in most of the model engine classes these days. They also introduce limits for plenum volumes under the venturi point to the valve as well.
Some great drawings that were shown. It is great to see what people have done quite a few years ago.
Neil

That's not completely true. Our GX twin boat racing class allows a two cylinder engine with a total of 64 cc. Unlike the G classes where only tuned pipes are allowed, there is no mention of super or turbo charging. A little turbo like the Garrett GT0632SZ Would be fun to experiment with.

Lohring Miller

[41juergen]

My musing is the square is the best comromise for a high revving and highest possible output two stroke
Undersqaure is the best compromise best for a mildly tuned MX 250.
The rod length is also likely a design compromise to keep the height down and or give a bettr ring life as the ring pack can be lower for a given height.


KTM200 has a nice long rod in 22mm crankpin
118mm


03.6248 ProX Con.Rod Kit KTM200SX-EXC ’98-16 20.00 28.00 118.00 15.90 15.90 151.40 94.00 22.00 55.00 22 x 37 x 1.0

Thank's for the help, unfortunately none would fit easy. So if the big end diameter is too small can I bore that up or is that hardened?

[Lightbulb]

Lohring, one thing that does work, is to have a fan like feature on the PTO drive , like on the outbord model engines. There is a 400 rpm gain over one that does not drive a PTO or a std PTO with the single or 2 slots.
Neil

[ceci]

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=342850&d=1567194042

Seeing it reminded me of Roland Holzmer's project, but he doesn't use the crank case to pump.
My question is: does a supercharged two stroke engine need the crank case?
Look for the answer here:

http://oa.upm.es/136/1/01199904.pdf

I'm not sure since everyone supports the M6 minarelli project with turbo that uses the crank case and not Roland Holzmer'

[ceci]

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=342850&d=1567194042

Seeing it reminded me of Roland Holzmer's project, but he doesn't use the crank case to pump.
My question is: does a supercharged two stroke engine need the crank case?
Look for the answer here:

http://oa.upm.es/136/1/01199904.pdf

I'm not sure since everyone supports the M6 minarelli project with turbo that uses the crank case and not Roland Holzmer'


Another question, the crankcase will not be a brake engine

[husaberg]

Thank's a lot for the feedback Wob. Have done a set of RGV250 barrels and they go into the engine soon.

Just one other question: I'm looking for a 115mm conrod with the following dimensions:
small end: diameter 21 mm, width min 16 mm
big end: diameter 31mm, width min 16mm
At least prox don't have an appropirate one, even with a wider width of the small or big end...


Thank's for the help, unfortunately none would fit easy. So if the big end diameter is too small can I bore that up or is that hardened?

Sorry i missed the original question. I just seen RGV so was thinking 22mm pin.
why are you looging for a conrod with those outside dimensions?
exctlu what crankpin dia and small end are you loking for. or is it 31mm crankpin??

i know MZ125 have crazy long lengths with 31 big ends
Big-end Width (mm): 16.9

Small-end Width (mm): 16.9

Big-end Bore (mm): 31

Small-end Bore (mm): 19

Center-to-center (mm): 125

Pin Diameter (mm): 25

Pin Length (mm): 49

Big-end Bearing (mm): 25*31*17

Small-end Bearing (mm): 15*19*20

Washer Thickness (mm): N/A


Or the NSR150
NSR150 110lc-c 21se 16.85 31mm KW6.

[TZ350]

My question is: does a supercharged two stroke engine need the crank case?

No. Commer Diesel come to mind. 342939

<iframe width="560" height="315" src="https://www.youtube.com/embed/JrAoj5Cuu68" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

[husaberg]

Nor does the Detroit family.

https://www.youtube.com/watch?v=nI3nmDL0R7Y

https://www.youtube.com/watch?v=b9H-K1MkVvM

https://www.youtube.com/watch?v=LM0POp26CVs

[jbiplane]

I finally succeed with injection and ignition boards with functionality close to 3 time more expensive Megasquirt 2 Extra
lite version for 1...4 cylinders
normal for 1...8 cylinders
At moment tested at -18...+80C on 4-stroke car engines
Going make -40 or -60C version
http://www.reaa.ru/yabbfiles/Attachments/MS2_Extra_size.jpg
http://www.reaa.ru/yabbfiles/Attachments/ms2_001.jpg
Some pins layout written on Russian, will make English docs soon

[peewee]

Thank's for the help, unfortunately none would fit easy. So if the big end diameter is too small can I bore that up or is that hardened?

if your talking about boring the hole in the crank wheel, that can be done as most cranks should have plenty of excess metal around the hole. ive got one bored 2mm larger if i recall. was couple years ago when i had it done. still holding together fine

[ken seeber]

Mid this year in the Netherlands I had the privilege to catch up with one of our 2 stroke technical legends, Frits Overmars. During this day, we visited a couple of locals, Henri Tiben and Martijn Stehouwer, both who are up there in the 50/125 cc racing scene. Getting the idea that this sounds strong, I asked the question “how often could you ever race?”, the answer being “every weekend if we wanted to”. I guess the tyranny of distance is less of an issue over there.

Anyways, Frits very generously gave me a library of pics, all carefully catalogued into various companies. I say generously, as this collection is a product of many years of his association with, and just good old passion for, something we are all here for. The 2 stroke. Must say it was quite humbling.

However the generosity was not to just me, but everyone here. Being a bit of a slack arse and distracted of late (again), figured it’s time to get them out there. Turns out that getting 2.2 GB of pics out there is not completely simple, certainly well beyond Kiwibiker’s posting limit.

DropBox has a 2 Gb limit so that’s out, but Google Drive is our friend here:

https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof?usp=sharing

Enjoy

342940

[speedpro]

A little turbo like the Garrett GT0632SZ Would be fun to experiment with.

Lohring Miller

Curse you :love:

[andreas]

Mid this year in the Netherlands I had the privilege to catch up with one of our 2 stroke technical legends, Frits Overmars. During this day, we visited a couple of locals, Henri Tiben and Martijn Stehouwer, both who are up there in the 50/125 cc racing scene. Getting the idea that this sounds strong, I asked the question “how often could you ever race?”, the answer being “every weekend if we wanted to”. I guess the tyranny of distance is less of an issue over there.

Anyways, Frits very generously gave me a library of pics, all carefully catalogued into various companies. I say generously, as this collection is a product of many years of his association with, and just good old passion for, something we are all here for. The 2 stroke. Must say it was quite humbling.

However the generosity was not to just me, but everyone here. Being a bit of a slack arse and distracted of late (again), figured it’s time to get them out there. Turns out that getting 2.2 GB of pics out there is not completely simple, certainly well beyond Kiwibiker’s posting limit.

DropBox has a 2 Gb limit so that’s out, but Google Drive is our friend here:

https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof?usp=sharing

Enjoy

342940

Nice!!!!!!

[AndreasL]

...our 2 stroke technical legends, Frits Overmars...

DropBox has a 2 Gb limit so that’s out, but Google Drive is our friend here:

https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof?usp=sharing



This is pure gold!
A big big thank you, Frits! And Ken of course.

Very happy that I took the time to catch up the approx 600 pages I was behind, haven’t been able to focus at 2-strokes for a while.

First reaction: I realized then (2-3 years ago) how much I have to learn...and now I have forgotten the main part of it and have to start over again.
Second reaction: This place is, still, unique. And that goes for the people, knowledge, willingness to share...and the gags.

Will keep lurking around until I hopefully find the time to continue with my on “lawnmower level” moped engine from the past and have something to share that maybe someone can take something from.
Even if it’s “what not to do” it can be very informative I have learned...:facepalm::laugh:

[Frits Overmars]

does a supercharged two stroke engine need the crank case?... I'm not sure since everyone supports the M6 minarelli project with turbo that uses the crank case.Don't let that Minarelli AM6 story fool you, Ceci. The world speed record obtained by the Buddfab team is well documentated; everybody has seen the pictures of their turbocharged engine, shown below once more. But there are one or two details that are less-known.
1: They claimed 24 hp. We have several Freetech bikes around, producing that kind of power on regular petrol, without any kind of mechanical supercharging.
2: For the actual world speed record they did not use the turbo-engine; they used a naturally-aspirating engine with a supplementary helping of nitrous oxide (last picture).
342948 342947 342946 342945



Mid this year in the Netherlands I had the privilege to catch up with one of our 2 stroke technical legends, Frits Overmars. During this day, we visited a couple of locals, Henri Tiben and Martijn Stehouwer, both who are up there in the 50/125 cc racing scene. Getting the idea that this sounds strong, I asked the question “how often could you ever race?”, the answer being “every weekend if we wanted to”. I guess the tyranny of distance is less of an issue over there.Ken, I remember you having a petrol chat with Henri Tiben while I was busy updating Henri's dyno. I wonder what you told him....
Anyway it worked: last week Henri became the 2019 European Freetech champion.

About that tyranny of distance: over here it's more a tyranny of proximity.
Australia has a population density of 3,1 people per km².
New Zealand is a bit more crowded, with 18 people/km².
In the Netherlands we 'enjoy' 488 people/km², so we'll have to think twice about going for a test-ride, severely risking to have our bike confiscated by the Law.
I lost a bike that way, before getting better acquainted with the local police who, although they always had to act on phone calls from angry residents, generously allowed for ten minutes delay on arrival, so I could make myself scarce before they turned up. That was 50 years ago (how time flies); life hasn't become any easier since then :p.

[lohring]

The issue is can you get enough boost from a turbo to make up for the extra complication over a tuned pipe. You probably will need an intercooler as well. That's easy on boats. My thought was to run two center bleed pipes that feed the turbo for a compact arrangement on a 90 degree V twin. For those who want to play with a sim I've attached more details of the Garrett below. EngMod runs very slowly and needs a lot of iterations for me. Let me know how it works for you.

Lohring Miller

342949

[ceci]

https://forums.kartpulse.com/uploads/default/original/1X/62d07825cce7e29dd8bf3544050fa2a53b509182.jpg

Thank you very much Frits.
I always thought that the disbelief shown on Facebook about Roland Holzner's project was for not using the crankcase.
But thanks to your statements I understand the basis of that distrust.

[Frits Overmars]

This place is, still, unique. And that goes for the people, knowledge, willingness to share...and the gags. Will keep lurking around until I hopefully find the time to continue with my on “lawnmower level” moped engine from the past and have something to share that maybe someone can take something from.
Even if it’s “what not to do” it can be very informative I have learned...:facepalm::laugh:..........
342950

[AndreasL]

..........
342950

Actually, I searched for that quote of yours last week.
My plan was to hang it at my office as a small reminder to my colleagues. :shifty:

[Frits Overmars]

Actually, I searched for that quote of yours last week.
My plan was to hang it at my office as a small reminder to my colleagues. :shifty:There's a lot more where this came from, thanks to Ken Seeber. go to https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof and download 'spreuken'.

[ceci]

I have made a mistake ?.
it has to rotate compressor impeller more than the crankshaft

[AndreasL]

There's a lot more where this came from, thanks to Ken Seeber. go to https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof and download 'spreuken'.

Will do for sure...have just reached the “Misc”-folder.
Still A LOT of information to go through. Fantastic!

OT: Funny how many Dutch words that’s understandable to a Swede. :niceone:

[Michael Moore]

Ken and Frits, thanks for making that material available, I'm looking forward to viewing it.


Does a typical modern 64-68mm 250 MX piston usually have enough material around the wrist pin to allow boring to take a 20mm pin instead of the common 18mm pin? I'd think that the strength concerns are at TDC when the pin is trying to pull down and out of the piston; BDC would have the pin forced into the body of the piston.

I suspect they may start out with a fairly generic casting/forging, but I don't know if they get trimmed on the underside of the piston below the pin (to save weight) enough to not leave sufficient material. Would it be a good plan to offset the new bore upwards so it just cleans up the bottom of the original bore and so removes minimal metal below the pin?

Any thoughts as to what is a good number for a safe minimum thickness below the pin for high RPM use?

thanks,
Michael

[OopsClunkThud]

Question about tuning for longer engine life:

I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

Questions:
With power being a combination of BMEP and RPM, do I have to give up both?

What has the largest impact on engine life?
1. Engine speed
2. torque/power
3. temperature
4. other

Given it's a forced air cooled engine, are there BMEP limits I should not expect to be able to exceed in sustained operation?

Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.

[katinas]

Ken and Frits, thanks for so helpful gallery. Bridgestone crank looks so nice.....
.
Add some tables from very old V.V. Bekman s "Road Racing Motorcycles" book and very old Fiat marine turbo-reed engine with trans higher than ex.

[AndreasL]

Frits or anyone with interest,

Going through your (Ken)-pictures I found the suggested pipe for the Trabant.
One can see that you have opted for a straight header section.

342956

This is in line with my own thoughts trying to not over scavenging my old (50cc moped designed in the 50-60:s) engine that, minus the RV intake, got way more similarities with the Trabi than the RSA...or anything with a descent 3-5 port layout.

As a general rule of thumb, should you suggest to start with a straight header and go from there with antic designs like this?

A friend with the same type of engine have tried all types of pipes, the last one a modern thing from a scooter. Way to extreme I say and I think he confirmed it with “more revs...but terrible dip, with fuel reversing out the carb, just before a final rush of power”.

He is at 190/131 duration so my take is that the “already to good pipe” even worsen the negative 2/3 of max hp-rpm dip and is even more pronounced by having optimal timings?

Will have a go in EngMod to see if the pressure traces can tell anything and if I’m able to hack a suggestion for a new (simple and basic) pipe together...one that works better that is. :rolleyes:
But any input is appreciated.

[F5 Dave]

Question about tuning for longer engine life:

I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

Questions:
With power being a combination of BMEP and RPM, do I have to give up both?

What has the largest impact on engine life?
1. Engine speed
2. torque/power
3. temperature
4. other

Given it's a forced air cooled engine, are there BMEP limits I should not expect to be able to exceed in sustained operation?

Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.

Disclaimer: I've never seen a lambretta in real life.

Temperature will be an issue so having a sleeve will be the worst thing you can do. Are there not aftermarket (ally, I assume they are iron stock?) Cylinders? - Edit: seems the internet is filthy with them.-

Rebuilding the crank with mx conrod parts if possible. And piston.

What usually fails in these things?

I'd also find a dirtbike stator and cdi for reliable sparks.

[F5 Dave]

Mid this year in the Netherlands I had the privilege to catch up with one of our 2 stroke technical legends, Frits Overmars. During this day, we visited a couple of locals, Henri Tiben and Martijn Stehouwer, both who are up there in the 50/125 cc racing scene. Getting the idea that this sounds strong, I asked the question “how often could you ever race?”, the answer being “every weekend if we wanted to”. I guess the tyranny of distance is less of an issue over there.

Anyways, Frits very generously gave me a library of pics, all carefully catalogued into various companies. I say generously, as this collection is a product of many years of his association with, and just good old passion for, something we are all here for. The 2 stroke. Must say it was quite humbling.

However the generosity was not to just me, but everyone here. Being a bit of a slack arse and distracted of late (again), figured it’s time to get them out there. Turns out that getting 2.2 GB of pics out there is not completely simple, certainly well beyond Kiwibiker’s posting limit.

DropBox has a 2 Gb limit so that’s out, but Google Drive is our friend here:

https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof?usp=sharing

Enjoy

342940
Golly. Thanks Frits and Ken. Epic.

[speedpro]

No expert on Lammys but they are fan force cooled which is a limiting factor for long periods running at speed. As F5 says the sleeve is a bad idea for the reason given. I've got a watercooled barrel coming for my scooter. Evidently this on it's own, leaving the head aircooled is sufficient. Or maybe not if it's 2-stroke.

[andreas]

I have made a mistake ?.
it has to rotate compressor impeller more than the crankshaft

Yes, considerably more.

[OopsClunkThud]

I know a sleeve adds a barrier to cooling, but it will still be an alloy cylinder with iron sleeve, better than the full cast iron as stock. One reason for doing this is that the cylinder spigot is only 3mm thick and this is a failure point, so bringing it back to a smaller bore and 4mm thickness should help (still really thin by modern 2T standards).

Not asking how to make a Lambretta reliable, wrong place for that, more about where to de-tune.

For example, to hit 25hp I could get there with:
6.0 BMEP @10,500rpm, mean piston speed of 20m/s
vs
7.5 BMEP @8500rpm, mean piston speed of 16m/s

Assuming I will have to sacrifice some BMEP, but do I? or is the wear mostly from piston speed and I could have 10 BMEP at 8000rpm for 30+HP (assuming I have the porting to do that)

[Pursang]

Question about tuning for longer engine life:

I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.

This is not the usual 11/10ths search for bucket HP. But ESE is a bit quiet and this is also where my head is at present.

I'm building up a Bultaco Metralla from over 40 years of parts collecting.
Not as a TSS race replica but just a strong, reliable, fun and useful weekend ride bike.
The Metralla probably provides a good model for your endurance Lambretta.

For a 100mph 250cc 1960's production bike, its state of tune was simple and mild, (just 2 little transfers) and almost identical to the Matador ISDT enduro bikes. They did not 'wear out' in a week, a month or even a year. Claimed 27bhp @ 7500 rpm.
(Racing kit lifted this to 32 @ 8200, about the same as the Pursang MX)

Frits & Wobbly have repeatedly advised that 'heat' is the nemesis of extracting power from air-cooled engines.
More HP production means way more waste heat to be dealt with.
Since HP = Torque X rpm, limiting the revs but maintaining sufficient torque to achieve the operational task is a good way to go with old air cooled engines. Any mods I do to the Metralla will be designed to keep the operating rpm at around the 7500 level.

Tons of info out there in google land about building tuned chambers to maximise peak HP, not much about pipes for general two stroke use. Wobbly provided some excellent information about de-tuned exhausts with plate baffles and their ability to extend powerbands well below & above the nominal tuned length rpm. Also about Vevey pipes with perforated rear cones in resonating chambers doing even better. One pipe software vendor now offers a similar option. I'd like to convert a standard Metralla plate baffled pipe to a perforated cone but haven't found any info about how to determine the required rear chamber volume.

For your project more cc and std rpm looks like a good way to go. Not sure how you change final gearing on a scooter, if needed.
A cast iron sleeve might be a barrier to cooling but in an old air cooled cylinder it also provides some dimensional stability.

Cheers, Daryl

[Michael Moore]

Patrick, I'm pretty sure I've read somewhere that wear increases with the square of the speed change so keeping a reasonable RPM on the scooter sounds like a good idea to me.

You might also look into some of the lubricant coatings for pistons/cylinders. They may need to be renewed periodically but your scooter probably isn't racking up lots of miles to where the cost would be exorbitant to refresh things. KalGuard, SwainTech, TechLine, etc.

Coming from a background of big 4t singles and twins for a street ride I'd probably shoot for a nice fat midrange power that lets the gearing be raised so you can still have a decent ride but not be pushing the RPM to the limit.

cheers,
Michael

[OopsClunkThud]

...Also about Vevey pipes with perforated rear cones in resonating chambers doing even better. One pipe software vendor now offers a similar option. I'd like to convert a standard Metralla plate baffled pipe to a perforated cone but haven't found any info about how to determine the required rear chamber volume...

thanks for that!

found this post on the topic, not sure yet how to model it in EngMod

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130788402#post1130788402

[Pursang]

thanks for that!

found this post on the topic, not sure yet how to model it in EngMod

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130788402#post1130788402

Yes that's the area, also a really good expanded one at 7:31 the day before (04 Nov 2014).

Not much info online, and it's all kart related. 'Vevey' pipes might have been originally created to satisfy noise restriction requirements for karts at the Vevey race circuit in the late 60's??? Earliest ones just had the perforated rear cone, then a 'silencer' box was added, then tuning of the box volume and finally pressure with stingers.
Some pics here about 'volume tuned' exhausts & other kart stuff.

If you work out how to EngMod it please let us know.

342961342962342963342964

Also the 2 stroke Wizard duel power pipe 342967

cheers, Daryl.

[peewee]

Successfully relocated pins:

https://forumbilder.com/images/2019/08/12/rings.jpg

good job mate. I thought of trying that horizontal pin method but I have no experience with it and lm sure I would of buggered it somehow :laugh:. instead I felt less nervous making a vertical hole to fit a needle bearing then closing the hole, since ive done it before on another pistons.

[Michael Moore]

peewee, did you peen the hole shut or give it a quick burst with a TIG welder to melt it shut?

[peewee]

peewee, did you peen the hole shut or give it a quick burst with a TIG welder to melt it shut?

i welded it shut with tig then used dremel bits to grind and make it smooth. 1/16 " blue tungsten . 135 amps on the machine then use the peddle according to what you need for the part. 1/16 4043 rod, 1 or 2 small dabs is enough. about 15cfh on the gas i think. 140freq. 65 balance. preheated the pistons alittle in the oven. take caution near the edge of the piston so it doesnt blow off.

[Flettner]

peewee, you from the USA, what is their obsession with this RK tech wrinkly squish area head? How is it supposed to work? Looks like a real bad machining job, chewed out.

[Frits Overmars]

Frits or anyone with interest, going through your (Ken)-pictures I found the suggested pipe for the Trabant. One can see that you have opted for a straight header section.
This is in line with my own thoughts trying to not over scavenging my old (50cc moped designed in the 50-60:s) engine...
As a general rule of thumb, should you suggest to start with a straight header and go from there with antic designs like this?
A friend with the same type of engine have tried all types of pipes, the last one a modern thing from a scooter. Way to extreme I say and I think he confirmed it with “more revs...but terrible dip, with fuel reversing out the carb, just before a final rush of power”.
He is at 190/131 duration so my take is that the “already too good pipe” even worsen the negative 2/3 of max hp-rpm dip and is even more pronounced by having optimal timings?You are right about about the exhaust timing, Andreas. 190° is just about ideal for a pipe, but the more effective a pipe is, the more it can, and will, mess up the torque curve below the power band.
The transfer timing plays a role too: the higher the transfers, the bigger the risk of wrongly-timed exhaust return pulses entering them.

You also have a point about overscavenging antique engines, but my main reason for giving that Trabbi pipe a straight header was much simpler: conical headers would have such a shallow angle that it would have been a lot of work to make them, for very limited returns, if any. And since it is not easy to fit two looong pipes in that little engine bay anyway, I tried to keep everything as makeable as possible, which included the possibility to bend the headers instead of building them from segments.
342989 342988

[Frits Overmars]

Frits very generously gave me a library of pics... I say generously, as this collection is a product of many years of his association with, and just good old passion for, something we are all here for: the 2 stroke... the generosity was not to just me, but everyone here. Enjoy. https://drive.google.com/drive/folders/18l2ShH-MzrnTO0uEk9rNTk89_KgwgWof?usp=sharingI collected those pics over a number of decades, initially for my personal use, so I never worried about copyrights. All pics marked with F©S were made by me and I hereby declare them copyright-free, but not all other pictures were, so you may want to give this a little thought before using them for publications.

[katinas]

Ken and Frits, thanks for making that material available, I'm looking forward to viewing it.


Does a typical modern 64-68mm 250 MX piston usually have enough material around the wrist pin to allow boring to take a 20mm pin instead of the common 18mm pin? I'd think that the strength concerns are at TDC when the pin is trying to pull down and out of the piston; BDC would have the pin forced into the body of the piston.

I suspect they may start out with a fairly generic casting/forging, but I don't know if they get trimmed on the underside of the piston below the pin (to save weight) enough to not leave sufficient material. Would it be a good plan to offset the new bore upwards so it just cleans up the bottom of the original bore and so removes minimal metal below the pin?

Any thoughts as to what is a good number for a safe minimum thickness below the pin for high RPM use?

thanks,
Michael

Michael, usually, for two stroke cycles, under pin material thickness is strong enough to hold things, even with weakened area for bigger pin. But for the cast pistons, all kinds of vibrations and detonation can propagate small cracks at weakened area.
Early Honda RS 500 triple pistons had 18mm piston pin and was prone to cracking around skirt, but later reduce to 16mm.

With forged piston you can do what you want…. Once at testing with 125, at 12000rpm , engine suddenly lost power accompanied with some metal sound, but engine still spinning, so return safely to home, 2 km , in first gear at 5000 rpm.
Take off the cylinder and cant believed. Short piston pin was hanging only on one side of piston eye as pin moves out because I forget to insert circlip. Results was that this forged piston pin eye ( 3.5 mm thick under pin ) was deformed and enlarged from 15 mm to 15.6mm, but not broken, after this 2 km riding. Cylinder left with typical rails on trans side.

Maybe, is it possible to find bigger small end bearing.

[katinas]

A friend with the same type of engine have tried all types of pipes, the last one a modern thing from a scooter. Way to extreme I say and I think he confirmed it with “more revs...but terrible dip, with fuel reversing out the carb, just before a final rush of power”.

He is at 190/131 duration so my take is that the “already to good pipe” even worsen the negative 2/3 of max hp-rpm dip and is even more pronounced by having optimal timings?




Once boy asked to help him prepare Yamaha Airox air cooled 100cc for scoot racing just two days before event. The only part that he bring , together with original scooter, was nice racing exhaust. After all usual work on engine was done until the evening, before next day race, he came to test and when return said that power just little bit better. After so much was changed, engine goes just marginally faster.
There is no time left to play with ignition and all variator/transmission stuff , so I ask him bring back his old rusty original exhaust and he was even more embarrassed.
After test riding he returns on one wheel, with a big smile. It was another engine.

[Tim Ey]

Question about tuning for longer engine life:

I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as

This sounds like a question for me!
The issue about Lambrettas is the super small transfer area since they got an asymetrical stud patern. Usualy, you get transferports worth for 80cc combined with exhaust area worth 150-300cc. The flow patern on the aftermarket cylinders are also not that nice & the cylinder is twisted somewhat 12° to the crankshaft & it is super hard to get a decent inlet, since the frame is limiting the inlet port.

In short: Tuning a lambretta is trying to win a horse race on a donkey.


If money is not an issue I would buy the killer case https://www.sip-scootershop.com/de/products/motorgehause+mmw+killer+case+_22010190 combine it with a SIP crankshaft and use the simonini 230
https://www.sip-scootershop.com/de/products/rennzylinder+simonini+mini+2_78246200
or simonini 270 cylinder
https://www.sip-scootershop.com/de/products/rennzylinder+simonini+mini+2_78246210
This will give to best powerband with VS fuel consumption.

There is an other case (CasaCase from Casa Lambretta) which is made for superwide crankshafts. I am currently working on one to get it flying (Rotary Inlet). See pictures here:
https://www.facebook.com/Overrev.me/?ref=bookmarks#

On the ignition I would suggest you use an Overrev Ignition (designed by me :shifty:) which you can get here https://1537118469.jimdofree.com/deutsch-1/overrev-z%C3%BCndung/ If you want one, write me a pn

Regards
Tim

[AndreasL]

You are right about about the exhaust timing, Andreas. 190° is just about ideal for a pipe, but the more effective a pipe is, the more it can, and will, mess up the torque curve below the power band.
The transfer timing plays a role too: the higher the transfers, the bigger the risk of wrongly-timed exhaust return pulses entering them.

You also have a point about overscavenging antique engines, but my main reason for giving that Trabbi pipe a straight header was much simpler...

Thank you for the answers. Good you mentioned the transfer timing as well. Perfectly logic, but I didn’t think about it.

Every design is a compromise. In racing, the one with the best one often bets the ones doing something extreme (in one or a few areas).
So sounds like a very wise decision to go for straight headers on the Trabbi. For several reasons.

I have to see what the owner says and what is reasonable to try.
But a comparison between, let’s say, a basic FOS-pipe with straight vs tapered header could be interesting. I have a feeling though that with the low level off tune we will see the same as you did. Small angles and differences in power. But who knows... The FOS is possibly “to much” as is. Test and see.

Would love to have a way to predict or at least get some cues when things start to go south regarding overscavenging. But since EngMod is 1D that’s not possible Neels told me.

[AndreasL]

...so I ask him bring back his old rusty original exhaust and he was even more embarrassed.
After test riding he returns on one wheel, with a big smile. It was another engine.

Thank you katinas.

A very good example that it’s physics that makes speed.
Not glossy ads and big names. (Exceptions exist) Without harmony in the design, one is lost though.

[peewee]

peewee, you from the USA, what is their obsession with this RK tech wrinkly squish area head? How is it supposed to work? Looks like a real bad machining job, chewed out.

i have no answer but if it works so good then how could the rest of the world be so stupid to not have figured it out as well. the way i look at it, how good something is, kind of depends what your comparing it against. we should all pitch in a few dollars to buy one then have wobbly test it against a known good design:laugh:. also remember that usa doesnt follow common reasoning . they would just as soon take a good plated cyl and bore it out to accept a iron sleeve

[Michael Moore]

Maybe, is it possible to find bigger small end bearing.

I have a 66mm Wiseco forged 2T piston here with 20mm pin, the thickness under the pin (bottom of bore to the outer forged surface) is 4.5mm. I presume they'd probably adjust the machining for different size pins to give a similar thickness from the forged surface. To get a 68mm piston "off the shelf" it would need to be an 18mm pin. Unfortunately the rod small end bore doesn't match the OD of any of the 18mm ID bearings that I find listed at Wiseco, ProX, etc. But since with a 68mm stroke that gives 232.6 cc instead of 250 there's a lot of appeal in ignoring the small loss of displacement for having a piston that doesn't need to be modified (and potentially messed up in the process). If done it will be a "hey it runs, it is a winner!" project, not a "crap, it is down .0005 hp on the competition, what a waste of time" project. :)

cheers,
Michael

[peewee]

forgot to mention what needle and drill bit i used. 1.95mm drill bit. needle is 1.98mm diam 9.71mm long. part# 0405222613 from ktm trans. ive got a few spare bearing if anyone needs some needles

[wobbly]

Did some last minute dyno work last week before winning the final round and NZ ProKart KZ title.
Not the latest cylinder design, but a prototype for the new R1 I needed to run in pistons for so outright power is down about 1.5 Hp.
First test is a stock , thin 0.8mm ring piston , with a 4* conical dome.
Next was a change to a new design with angled squish only then a flat top , with new insert to suit that brings the plug down
4mm closer to the piston face.
Last test was the " fluid diode " in the boost port - 3mm around 3 sides.
Picking up 1/2 a Hp in an afternoon with no failed ideas was a bit of a surprise.
Comparing this new settup with NT software , using live track data , and the latest cylinder showed closer to 0.8HP and resulted
in a qualifying time 0.3 secs under the lap record.

[lodgernz]

good job mate. I thought of trying that horizontal pin method but I have no experience with it and lm sure I would of buggered it somehow :laugh:. instead I felt less nervous making a vertical hole to fit a needle bearing then closing the hole, since ive done it before on another pistons.

Peewee, did you block the old pinholes? Wouldn't want to reduce the gas pressure behind the rings by leakage.

[peewee]

Peewee, did you block the old pinholes? Wouldn't want to reduce the gas pressure behind the rings by leakage.

some pages back it seems i showed what i did. tried drilling the old pin flush with the back of the ring groove but the pin is just to hard for that small of drill bit and causes deflection of the bit. thought about trying a very small carbide end mill bit to make the pin flush with the back of the groove. that idea likely would of worked but the end mill bit was atleast 7-10 days out from getting to my house. on hand i had some mini dremel cutting disks that fit nice in the ring groove so i carefully grinded the pins flush with the back of the groove. i didnt drill out the pin and make a hole into the piston onderside. if i ever relocate pins again, ill probly try the small carbide end mill just for fun. hek i may even try it on a old piston just to see if it works as well as i think

[TZ350]

.
Posted for no other reason than to show the possibilities with bending the fueling curve.

342996

Red is a rich main jet, Blue a smaller one that made best power.

The trick is to plump up the fueling curve with a solenoid power jet or trim off the top with the air correction jet to get the best curve.

A whole lot easier with EFI of course.

[Pursang]

.
Red is a rich main jet, Blue a smaller one that made best power.


I can understand significant power variations with mixture adjustments... but where/why/how does 1500rpm actually disappear with the richer mixture??
Rich enough to put the fire out??...:confused:

Cheers, Daryl

[TZ350]

Rich enough to put the fire out??...:confused:

Remember a carburetors air/fuel ratio at WOT becomes increasingly rich as the air flow through it increases with increasing rpm unless there is some sort of fuel correction.

My guess is that the Red line is rich enough to change the wave action in the pipe.

Basically the rich mixture and therefor cooler exhaust gas makes the pipe seem longer than it is. So it cuts the revs of earlier than it should. In much the same way that retarding the ignition and leaning off the mixture puts heat into the pipe. Making it seem ever shorter thereby extending the wave action over higher rpm. Play with the fuel (and ignition timing) and you could get three pipes for the price of one.

343001

Make it rich at the bottom for "drive" (Red line) then progressively correct the fuel at the upper rpm (top part of the Blue line) for "max power" and "over rev". Ignition plays it's part too.

Anyway for what its worth, that is my take on it..........

[Pursang]

Play with the fuel (and ignition timing) and you could get three pipes for the price of one....
Anyway for what its worth, that is my take on it..........

Very Cool TZ.. Certainly shows the value of back to back Dyno testing! And Wobbly's incremental improvements do too.

One could drive him/her self crazy trying to sort that out using 'butt on the seat' tuning....:spanking:

I myself have obviously have spent way too long in "full power rich" tuning mode. (That's fuel Not money)

Cheers, Daryl.

[AndreasL]

.
Posted for no other reason than to show the possibilities with bending the fueling curve.

342996

Red is a rich main jet, Blue a smaller one that made best power.

The trick is to plump up the fueling curve with a solenoid power jet or trim off the top with the air correction jet to get the best curve.

A whole lot easier with EFI of course.

This was a real eye opener post for me! Great!

Having read “turn off the PJ around peak power” so many times here, my reaction has more or less been “off course you do...it makes perfect sense”.

Now I remember that I have read about the effect off the air correction jet before and all came together.

Knowing and understanding is two different things I guess.

Thanks TZ!

[Pursang]

Here's Something that might be useful for Something.

343003

Perhaps someone, limited by something (say.. long parallel header pipes) could use something like this to rapidly diverge exhaust flow to a large diameter belly section, or something.

Concepts of suitable wave duration profiles and timings would need reconsideration or something.

[katinas]

Did some last minute dyno work last week before winning the final round and NZ ProKart KZ title.
Not the latest cylinder design, but a prototype for the new R1 I needed to run in pistons for so outright power is down about 1.5 Hp.
First test is a stock , thin 0.8mm ring piston , with a 4* conical dome.
Next was a change to a new design with angled squish only then a flat top , with new insert to suit that brings the plug down
4mm closer to the piston face.
Last test was the " fluid diode " in the boost port - 3mm around 3 sides.
Picking up 1/2 a Hp in an afternoon with no failed ideas was a bit of a surprise.
Comparing this new settup with NT software , using live track data , and the latest cylinder showed closer to 0.8HP and resulted
in a qualifying time 0.3 secs under the lap record.


Wob, glad to hear that fluid diode did not disrupt power, thank you very much for this tests info.
With 3mm crankcase step, it is possible to grind "riverbed" on case, for little more resistance.

[guyhockley]

I collected those pics over a number of decades, initially for my personal use, so I never worried about copyrights. All pics marked with F©S were made by me and I hereby declare them copyright-free, but not all other pictures were, so you may want to give this a little thought before using them for publications.

Not sure that Tony Foale's book should be there from a legal or copyright point of view...

[Frits Overmars]

Not sure that Tony Foale's book should be there from a legal or copyright point of view...You're quite right Guy, thanks. I only thought about removing Blair's book before making the collection public, but I missed Tony's book. I'll have it removed right away.

[ken seeber]

You're quite right Guy, thanks. I only thought about removing Blair's book before making the collection public, but I missed Tony's book. I'll have it removed right away.

Gone already, not the intention. :Oops:

[mantonakakis]

Hoping for a sanity check on inertial dyno roller/flywheel design (herein referred to as "roller"). If you feel like reading/thinking through all of this, please feel free to let me know if I have anything wrong here.
Otherwise, feel free to use this for your own dyno, if you trust my math ;) I can share a spreadsheet if anyone is interested.

I am hoping to build a (hopefully portable) dyno at some point, mostly for 50cc engines -- but I am quickly realizing that engine size/power might not be the most important design input parameter for an "ideal" 2T dyno; rather the mass of the bike and rider may be the only important parameter. More specifically, for a chassis dyno with a thin-wall roller, the roller mass should be equal the mass of the bike+rider. Things can get a little more complicated for a engine dyno that operates from the transmission output shaft, with corrections needed for sprocket ratio and roller vs. tire diameter, but same basic concept.

The core assumption comes from what I remember reading here: that for 2T development purposes, it seems there is some consensus that the "best" way to use a dyno is to replicate on-track usage; in other words, steady-state readings are not as useful as inertial readings while replicating on-track acceleration, in (large) part due to heat rates (e.g. exhaust temp). Please correct me if I am wrong, but if this is correct, then the dyno roller's inertia should replicate the mass of the bike and rider.

The math:
The equivalent mass (i.e. converting to linear kinematics) of a dyno roller is given by the following equation (http://hpwizard.com/rotational-inertia.html):

mequivalent = Iroller * (1 / rroller)2
Assuming the roller's circumferential speed matches the rear tire's circumferential speed, as on a chassis dyno, we just need to get the roller's equivalent mass to match the on-track mass.
With the equivalent-mass equation above, and the equations for roller inertia:

I ~= mthin roller * rthin roller2, or

I = 1/2 * msolid roller * rsolid roller2,
the roller radius cancels itself out - so assuming the roller's circumferential speed matches the tire's circumferential speed:

mthin roller ~= mbike+rider, or

msolid roller = 2 * mbike+rider

Correction for engine dyno:
If, however, the circumferential speeds differ (as can be the case with an output-shaft driven roller), the equivalent mass does change, by a factor of the speed ratio (roller circumferential speed / tire circumferential speed, or roller radius / tire radius) squared. So if the roller has the same mass as bike+rider but half the diameter of the tire and is driven at the same angular velocity as the tire, it acts roughly like 1/4 of the mass of bike+rider - of course only applicable for an output shaft-driven roller (not a chassis dyno).

So two key takeaways here: thin-wall roller is most mass-efficient (of course); and to best simulate on-track usage (for a chassis dyno with said thin-wall roller), the roller mass should simply be roughly equal to the bike + rider mass.
Therefore if I want portability, like being able to put the dyno in the back of a truck by myself, I need to overdrive the roller to be able to reduce its mass sufficiently (so a chassis dyno will not work due to the required roller mass).


Personal Example:
I am working on a 50cc moped with a single-speed centrifugal clutch transmission. Let's say that currently the specifications are:

Primary Ratio: 16:57 = 1:3.5625
Chain Drive: 10:60 = 1:6
Total Gear Ratio: 21.375
Tire Radius, rolling: 0.281m
Mass of bike and rider: 127kg
Maximum Engine Speed: 15,000rpm
This gives a top speed of 46.2mph (74.3km/h).

Let's also assume my roller specifications, for an engine dyno driven by the transmission output shaft, are:

Mass: 20kg
Material: A36 steel, 7800kg/m3, 250MPa Yield Strength
Radius: 15cm
Thickness: 1.5cm
Length: 19.09cm
Inertia: 0.407kg/m2

If I spin this roller at the same angular velocity as my tire, i.e. if I use 10:60 sprockets for the roller drive, then the equivalent mass of the roller is 5.16kg. Not nearly enough! This is derived from:

mequivalent = Iroller * (omegaroller / vtire)2
...where the previous variables relate to engine speed by:

omegaroller = omegaengine * gear ratioroller, total, and
vtire = omegaengine * rtire / gear ratiotire, total
Thus the equivalent roller mass equation is:

mequivalent, roller = Iroller * (Zrear, tire * Zfront,roller / (Zfront, tire * Zrear, roller))2 * (1 / rtire)2
...where the "Z" values are the tooth counts for each sprocket.
To get the equivalent mass to match up as closely as possible, I need to swap the roller shaft sprocket to a 12-tooth to overdrive it 5x as fast. Doing so gives an equivalent mass of 129kg, with a roller angular velocity of 3509rpm at 15000rpm on the crankshaft. A hoop stress calculation shows ~23.7MPa:

stress = mroller * rroller2 * omegaroller2
If I gear the moped for top speed rather than acceleration, say close to 80mph, I might use a sprocket ratio more like 12:42 for the bike, in which case my equivalent mass with a 12:9 sprocket ratio for the rollers is about 112kg (this is probably the practical limit to sprocket sizes). Hoop stress here is about 60MPa, so seems like it would still be safe.

[wobbly]

My experience with engine type dyno is that you need to replicate somewhat a relevant acceleration rate as seen on track.
This varies of course with each gear ratio , so the acceleration rate needs to refactored to give sufficient run time that the
pipe temp reflects that as seen on track.
In my case with the inertia I chose and using 6th gear I changed the sprocket drive ratio until a full throttle run from 7000 to 15000
took around 9 secs.
I do a couple of all gear runs , once the water temp has stabilised at around 40*C , to heat the pipe wall temp , then do 3 6th gear
dyno recorded pulls.
These are combined to give an averaged data set.
The pipe temp in the header starts at around 450*C and I always rejet to see 630*C at the end of the pulls.
This method was later checked as being spot on accurate , when I purchased NT software that uses our on track data logger info to show
actual Hp delivered.
The peak power was with 2/10 and the peak power rpm was within 200.
But most important was that the results are always repeatable using the same test regime for every session.

[mantonakakis]

Thanks Wobbly!
I've got questions regarding jetting and EGT (for the same aforementioned project), but I think I should get a little more hands-on time before asking. I think I understand the basics, but things might be a little complicated by my almost 2000m elevation in Colorado.
Hopefully this "try first, ask later" approach doesn't result in me asking how to un-hole my piston ;)

[peewee]

heys guys i need to make some thrust washers for the small end of the rod and bearing. easily accesible materials i can use are aluminum, copper, brass, zinc, nickel silver ( mix of copper, nickel, zinc ?). is copper my best choice ?

also has anyone made theyre own oiling slot or holes in the rod small end ?

[F5 Dave]

My experience with engine type dyno is that you need to replicate somewhat a relevant acceleration rate as seen on track.
This varies of course with each gear ratio , so the acceleration rate needs to refactored to give sufficient run time that the
pipe temp reflects that as seen on track.
In my case with the inertia I chose and using 6th gear I changed the sprocket drive ratio until a full throttle run from 7000 to 15000
took around 9 secs.
I do a couple of all gear runs , once the water temp has stabilised at around 40*C , to heat the pipe wall temp , then do 3 6th gear
dyno recorded pulls.
These are combined to give an averaged data set.
The pipe temp in the header starts at around 450*C and I always rejet to see 630*C at the end of the pulls.
This method was later checked as being spot on accurate , when I purchased NT software that uses our on track data logger info to show
actual Hp delivered.
The peak power was with 2/10 and the peak power rpm was within 200.
But most important was that the results are always repeatable using the same test regime for every session.

That is interesting. I don't have. . .I'm going to say 'my' dyno, anymore, but had certain routines to get consistent results as possible. However I will venture that mine were clearly a compromise as despite the pretty serious 4ft industrial fan I didn't have enough cooling to do as you stated.

[jato]

heys guys i need to make some thrust washers for the small end of the rod and bearing. easily accesible materials i can use are aluminum, copper, brass, zinc, nickel silver ( mix of copper, nickel, zinc ?). is copper my best choice ?

also has anyone made theyre own oiling slot or holes in the rod small end ?

I expect someone will be along with an exact recommendation in due course but keep in mind a hi spec 125 will typically subject those small end washers to 5000 odd G's about 200 times a second so will destroy anything but a "tough" metal so that rules out copper , ally , and brass and possibly nickel silver (do you know the % of the mix? ). I know the last 1000rpm used to shorten the life of the hardened steel ones used in some of the 80's race bikes. what stroke and rpm are you looking at?

[F5 Dave]

We used hardened steel washers out of some Honda . They lasted ok but needed to be checked and changed as they brinneled eventually.

[Frits Overmars]

...the roller mass should simply be roughly equal to the bike + rider mass.You can forget all about the mass of bike and rider. You said it yourself, and Wobbly dotted the i's: you need to replicate the acceleration rate as seen on the track.
That is a value you can measure, and though the mass of bike and rider will have a direct influence on the acceleration rate, those masses themselves are irrelevant.


if I want portability, I need to overdrive the roller to be able to reduce its mass sufficiently (so a chassis dyno will not work due to the required roller mass).There are several dynos with a wheel-driven drum geared to a flywheel that spins at double the drum rpm, with 1/4 of the inertia and the mass that the drum would otherwise need to have. Below are some portable examples, with and without upgeared flywheel.
343013 343012 343011

[mantonakakis]

Thanks Frits, very helpful, as always.
With good controls, I suppose a brake dyno could also be made to replicate on-track acceleration, and potentially weigh less, at least if there's enough heat capacity built in for a test cycle like Wobbly described.
Convert output torque or power as measured to the acceleration that would result with specified mass and "road load" constants (can be found with a coast-down test), and set up a closed-loop control of output speed... Of course you would still want to be sure to include rotational inertia into the torque calculation.
A few years ago I worked on automatic transmission calibration for Toyota, and our multi-million dollar chassis brake dyno seemed to read about half of the actual torque when accelerating in first gear... I suspected that despite its high price tag, the manufacturer forgot to include the substantial roller inertia in their torque calculation. Maybe they assumed their dyno (which had a "road load" mode to simulate driving on the road) would only be used for steady-state testing?

Another interesting memory - the US EPA allows OEMs to conduct their own fuel economy and emissions testing in-house. The chassis dyno we used for that testing had a screen that the driver could view, with the most boring video game in the world. There was a continuously scrolling target speed plot (the official test cycle), with a dot showing the current wheel speed. The operator "drives" the car, using both pedals to change speed as needed, doing their best to keep the dot on the line. There are obvious ways to cheat the test (since it is done in house on good faith), but the EPA allows it to happen this way regardless. I guess they don't have the budget to do it all themselves?
Anyway, this reminded me of a previous discussion I saw here about using a dyno to simulate actual tracks, and I imagine the same methodology would work - derive your road load from a coast-down test and use previous track data to generate the test cycle (target speed trace? Or perhaps use a distance-based cycle instead, or ideally some combo, since you still want to measure maximum engine performance in the areas of the track where you can go full throttle). From my experience, the biggest challenge will be to stay awake! Or maybe a race simulation is more engaging than a fuel economy cycle...

[lohring]

My inertial dyno experience is with engine driven flywheels and smaller engines. If you would be interested I wrote an article on these dynos at namba.com/content/library/propwash/2019/april/16/ I have a spreadsheet that calculates some of the factors like stress and acceleration for this style flywheel. Below is a picture of our dyno.

Lohring Miller

343014

[mantonakakis]

My inertial dyno experience is with engine driven flywheels and smaller engines. If you would be interested I wrote an article on these dynos at namba.com/content/library/propwash/2019/april/16/ I have a spreadsheet that calculates some of the factors like stress and acceleration for this style flywheel. Below is a picture of our dyno.

Lohring Miller

343014

Thank you, Lohring!

[Haufen]

Hoping for a sanity check on inertial dyno roller/flywheel design (herein referred to as "roller"). If you feel like reading/thinking through all of this

I did not. Maybe I will give it a go later on. But if you yould like to know ideal dimensions / setup of an engine dyno to duplicate real road conditions, you can do that with the excel sheet from sportdevices. For a simple single roller the weight of the drum shall be twice the vehicle weight (including driver) to get 1:1 conditions (i.e. 4th gear pulls take just as long as on the road)

Sportdevices Excel File Download (https://www.sportdevices.com/download/rollerssheet.xls)
Dyno download page (https://www.sportdevices.com/download.php)

[mantonakakis]

I did not. Maybe I will give it a go later on. But if you yould like to know ideal dimensions / setup of an engine dyno to duplicate real road conditions, you can do that with the excel sheet from sportdevices. For a simple single roller the weight of the drum shall be twice the vehicle weight (including driver) to get 1:1 conditions (i.e. 4th gear pulls take just as long as on the road)

Sportdevices Excel File Download (https://www.sportdevices.com/download/rollerssheet.xls)
Dyno download page (https://www.sportdevices.com/download.php)

I don't blame you!
Their calculations give the same results as mine, so that sanity check is complete.
And the conclusion of 2x vehicle weight matches too (for a 1:1 wheel:roller circumferential speed ratio and solid roller).

[F5 Dave]

Thanks Frits, very helpful, as always.
With good controls, I suppose a brake dyno could also be made to replicate on-track acceleration, and potentially weigh less, at least if there's enough heat capacity built in for a test cycle like Wobbly described.
Convert output torque or power as measured to the acceleration that would result with specified mass and "road load" constants (can be found with a coast-down test), and set up a closed-loop control of output speed... Of course you would still want to be sure to include rotational inertia into the torque calculation.
A few years ago I worked on automatic transmission calibration for Toyota, and our multi-million dollar chassis brake dyno seemed to read about half of the actual torque when accelerating in first gear... I suspected that despite its high price tag, the manufacturer forgot to include the substantial roller inertia in their torque calculation. Maybe they assumed their dyno (which had a "road load" mode to simulate driving on the road) would only be used for steady-state testing?

Another interesting memory - the US EPA allows OEMs to conduct their own fuel economy and emissions testing in-house. The chassis dyno we used for that testing had a screen that the driver could view, with the most boring video game in the world. There was a continuously scrolling target speed plot (the official test cycle), with a dot showing the current wheel speed. The operator "drives" the car, using both pedals to change speed as needed, doing their best to keep the dot on the line. There are obvious ways to cheat the test (since it is done in house on good faith), but the EPA allows it to happen this way regardless. I guess they don't have the budget to do it all themselves?
Anyway, this reminded me of a previous discussion I saw here about using a dyno to simulate actual tracks, and I imagine the same methodology would work - derive your road load from a coast-down test and use previous track data to generate the test cycle (target speed trace? Or perhaps use a distance-based cycle instead, or ideally some combo, since you still want to measure maximum engine performance in the areas of the track where you can go full throttle). From my experience, the biggest challenge will be to stay awake! Or maybe a race simulation is more engaging than a fuel economy cycle...

I presume the EPA has upgraded the sw, so now you can pull over, rob banks, run over people and pick up hookers. :laugh:

[peewee]

I expect someone will be along with an exact recommendation in due course but keep in mind a hi spec 125 will typically subject those small end washers to 5000 odd G's about 200 times a second so will destroy anything but a "tough" metal so that rules out copper , ally , and brass and possibly nickel silver (do you know the % of the mix? ). I know the last 1000rpm used to shorten the life of the hardened steel ones used in some of the 80's race bikes. what stroke and rpm are you looking at?


We used hardened steel washers out of some Honda . They lasted ok but needed to be checked and changed as they brinneled eventually.

ive no experience with small end washers so i wasnt sure what material to use. not sure what the nickel silver mix would be. 60-20-20 perhaps but i would have to make some phone calls to be sure. would titanium do ok? i could get some of that easy enough. the engine only has to run for a few hours each summer. 58mm stroke at about 10k rpm

did the hardened steel wear a groove and lip in the wristpin and prevent it from being removed out of the piston pin bore ?

[peewee]

(do you know the % of the mix? ).

its this https://www.onlinemetals.com/en/product-guide/alloy/770%20nickel%20silver

[41juergen]

Thanks Frits, very helpful, as always.
With good controls, I suppose a brake dyno could also be made to replicate on-track acceleration, and potentially weigh less, at least if there's enough heat capacity built in for a test cycle like Wobbly described.
Convert output torque or power as measured to the acceleration that would result with specified mass and "road load" constants (can be found with a coast-down test), and set up a closed-loop control of output speed... Of course you would still want to be sure to include rotational inertia into the torque calculation.
A few years ago I worked on automatic transmission calibration for Toyota, and our multi-million dollar chassis brake dyno seemed to read about half of the actual torque when accelerating in first gear... I suspected that despite its high price tag, the manufacturer forgot to include the substantial roller inertia in their torque calculation. Maybe they assumed their dyno (which had a "road load" mode to simulate driving on the road) would only be used for steady-state testing?

Another interesting memory - the US EPA allows OEMs to conduct their own fuel economy and emissions testing in-house. The chassis dyno we used for that testing had a screen that the driver could view, with the most boring video game in the world. There was a continuously scrolling target speed plot (the official test cycle), with a dot showing the current wheel speed. The operator "drives" the car, using both pedals to change speed as needed, doing their best to keep the dot on the line. There are obvious ways to cheat the test (since it is done in house on good faith), but the EPA allows it to happen this way regardless. I guess they don't have the budget to do it all themselves?
Anyway, this reminded me of a previous discussion I saw here about using a dyno to simulate actual tracks, and I imagine the same methodology would work - derive your road load from a coast-down test and use previous track data to generate the test cycle (target speed trace? Or perhaps use a distance-based cycle instead, or ideally some combo, since you still want to measure maximum engine performance in the areas of the track where you can go full throttle). From my experience, the biggest challenge will be to stay awake! Or maybe a race simulation is more engaging than a fuel economy cycle...

Come one, a FTP-75 or a WLTC is not too hard to stay awake...:sleep: but of course you are right, that is very boring to run this tests on chassis dyno.
But if you go into Hybrids, running from "depleting" into "sustainable" mode it can take some hours :blink:
We will take robots in the future to do that (like an OEM is now doing in their new certification center in Korea).

[41juergen]

if your talking about boring the hole in the crank wheel, that can be done as most cranks should have plenty of excess metal around the hole. ive got one bored 2mm larger if i recall. was couple years ago when i had it done. still holding together fine

Sorry for the late response peewee. Maybe my wording was not perfect :innocent: : I'm looking for a conrod that fits to my requirements (want to get a longer rod into the TZ250 4DP engine) and I only can get e.g. Banshee 115 mm rods, but the big end bearing in them is too small to fit the 4DP crank big end pin...
I also checked the other recomendations and tips, unfortunately without success...

[jato]

its this https://www.onlinemetals.com/en/product-guide/alloy/770%20nickel%20silver

I'm not so sure about the nickel silver either now - i see its heavier (12%) than steel and not much stronger than mild steel . 4140/4340 with nitriding could be a likely candidate .
Titanium also but we need someone experienced with that to chime in ...

[F5 Dave]

ive no experience with small end washers so i wasnt sure what material to use. not sure what the nickel silver mix would be. 60-20-20 perhaps but i would have to make some phone calls to be sure. would titanium do ok? i could get some of that easy enough. the engine only has to run for a few hours each summer. 58mm stroke at about 10k rpm

did the hardened steel wear a groove and lip in the wristpin and prevent it from being removed out of the piston pin bore ?
In my case no the wristpin was not damaged by running thrust washers. It was a very long time ago but I think there was reasonable clearance, in fact I was running them only as the piston was wider than stock so I had to contain the bearing.

[TZ350]

343016 343017 343018

These are hardened steel washers from a Suzuki RGV250. 0,010" side clearance (0,254mm). Very close slip fit on the pin and no appreciable grooving of the pin after hours of service. These washers are used to centralize the rod when no big end washers are being used. I have seen steel and hard anodized aluminium in Yamaha KT100 cart engines. I was not that impressed with the life of the alloy KT100 ones. I would think washers made out of any good quality steel would be fine. I don't think hardening would be all that necessary for a short run competition engine.

[peewee]

I'm not so sure about the nickel silver either now - i see its heavier (12%) than steel and not much stronger than mild steel . 4140/4340 with nitriding could be a likely candidate .
Titanium also but we need someone experienced with that to chime in ...


In my case no the wristpin was not damaged by running thrust washers. It was a very long time ago but I think there was reasonable clearance, in fact I was running them only as the piston was wider than stock so I had to contain the bearing.




These are hardened steel Suzuki RGV250. 0,010" side clearance (0,254mm). Very close slip fit on the pin and no appreciable grooving of the pin after hours of service. These washers are used to centralize the rod when no big end washers are being used. I have seen steel and hard anodized aluminium in Yamaha KT100 cart engines. I was not that impressed with the life of the alloy KT100 ones. I would think washers made out of any good quality steel would be fine. I don't think hardening would be all that necessary for a short run competition engine.

yes i only need washers to keep the small bearing centered as the piston is wider than standard. like you say, im sure most any steel would work for a short run engine. theres plenty of stainless steels that i can get and im sure they would be fine so thats probly what ill use. titanium grade 2 is cheap enough but i have no experience with it.

ive got 2mm total gap of the small bearing and piston. my plan is to use atleast .5mm washers so ill have 1mm total gap. .5mm each side of bearing. i could probly make even slightly thicker washers for .25mm gap on each side of the piston, which might be a better choice. thnks guys ill get the material ordered and not over think it

havent decided yet but might drill some oiling holes at the 2 and 10 oclock position on the rod small end. although maybe they arent needed for a short run engine

[Niels Abildgaard]

titanium grade 2 is cheap enough but i have no experience with it.



Titanium is NO bearing alloy.
It seizes on anything.
A bitch in heat.

[katinas]

Yes, titanium, without special coatings, is worst material (especially pure titanium grade 1 and 2) for sliding pairs.
Titanium is unique material, in vacuum and argon gas, friction is lower than cooper, Al and iron. But in a real environment, its opposite, because naturally the titanium outside oxide layer are very thin and broke easy at contact place. Then, very reactive under oxide metal layer quickly stick to other parts. Thermal conductivity is low and absolutely no adhesion with any oils, even more worsened things.

I try polyamide-imide Torlon 4301 for small end side washers and they work. But still needed more test. Torlon 4203 is little stronger, but without additional PTFE and graphite. Is less wear resistant, but with oil around no big difference.
On special pocketed piston with narrow inside, tested without any washers, so piston inner sides directly centered conrod. It works without any troubles.

[oldjohnno]

These are hardened steel Suzuki RGV250. 0,010" side clearance (0,254mm). Very close slip fit on the pin and no appreciable grooving of the pin after hours of service. These washers are used to centralize the rod when no big end washers are being used. I have seen steel and hard anodized aluminium in Yamaha KT100 cart engines. I was not that impressed with the life of the alloy KT100 ones. I would think washers made out of any good quality steel would be fine. I don't think hardening would be all that necessary for a short run competition engine.

I've had good results with steel washers as well. I machine them from some big socket head capscrews I have on hand, not super hard but very tough, grade 12.9 on the metric scale or around 170,000 psi in old speak. Once they're parted off I polish the sides on some fine wet and dry on a surface plate.

[TZ350]

yes i only need washers to keep the small bearing centered as the piston is wider than standard.

For that I would follow Oldjohnno's suggestion's and if you don't need to locate the rod then only make the washer diameter big enough for the L/E bearing so as to not restrict lubrication.


I've had good results with steel washers as well. I machine them from some big socket head capscrews I have on hand. Once they're parted off I polish the sides on some fine wet and dry on a surface plate.

[jbiplane]

Want to share this info. For 30 USD possible get real miracle :) Or not ?
https://vano.en.alibaba.com/product/62211417779-802114354/Plastic_Enclosure_Motorcycle_ECU_Connector_Exciter _150_Motorcycle_ECU_BOX.html

[mantonakakis]

Want to share this info. For 30 USD possible get real miracle :) Or not ?
https://vano.en.alibaba.com/product/62211417779-802114354/Plastic_Enclosure_Motorcycle_ECU_Connector_Exciter _150_Motorcycle_ECU_BOX.html

It has a clutch! Awesome!

"featuring high fit accuracy, flexible movement of the pressure plate within the axial stroke,accurate return, and freedom from seizure, with small axial pressure at clutch meet and large static friction coefficient"

[mantonakakis]

We tested a winning Quad at Pikes Peak ,and the A/F was at 12.8:1 at the bottom, and 12.8:1 at the top - I couldn't believe it.
If you (or anyone else in this thread) ends up at Pikes Peak again, the beer (or other beverage of choice) is on me! I found exactly what I was looking for to fix my confusion re: carbs' circuits referred to mainly/only by throttle position and not engine speed.

[peewee]

preparing the pistons. all grinded surfaces i polished smooth

[oktrg500]

Hi,

I have been a daily lurker here since I discovered this thread a long time ago. A huge thanks to all for the knowledge being shared here.

Norway is a small country and there's not many dyno's around. As far as I'm aware, the only shop I would trust doing a two stroke dyno run is too far away for my budget. So, plug chops and seat of the pants dyno it is.

What buggers me a lot, is how to judge the smoke ring after WOT. I've always wanted to get to the bottom of this:
Quite a few people say you must look at both the width of the ring and the color of the ring.

I have experienced the color of the ring, and what the color looks like around the circumference of the porcelain is what I should pay attention to.

Is the width of the ring of any importance? If so, I'd like to understand how the color and the width relates to each other.

Attached is pics of a plug chop of my wifes scooter. I don't want to risk the wrath of my wife because the scooter seized. At the time this plug chop was done I think I could have used a smaller main jet and still be safe. Am I right thinking so?

[TZ350]

.
Welcome Octrg500

These are some earlier posts I found using the Google "site:" search option.

There may be other, better posts, cut and paste this into the search bar " plug reading site:https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner "

For the quotes below you will need to click through to the original posts to read the full story. Click on the little blue box that is after each posters ID.


275922 275923

B9 plug after Tokoroa.

B10 plug after Taumarunui

275921 275920

The B10 plug from Taumarunui after some hot laps and a proper plug chop before over rev deto set in. I would be interested in what Wob has to say about it.

Quite a bit on page 600 too.


276053 276054

Yes, Wob I would be very keen to know if the colour of the B10's fuel ring is more like you would expect.

343051 a bit lean for unleaded fuel.


Is this still running AvGas??
For Av its a bit rich, for Unleaded its a bit lean.
The plug heat range appears good, and the mixture is on the rich side of correct for Av.


This plug reading stuff is very interesting I have always wondered how it was done. Cutting open a plug each time looks like a real dedicated way of doing it.

276171 276172 NGK B9 Plug

276170 276169 NGK B10 Plug

I know (because I asked) the B9 and B10 plugs were new and fitted into a hot (up to temperature) 2T engine after practice and plug chopped at the end of one race each so there is not much running time on them.

Is it because the ones below are 4T that there is no (oil ???) stain on the nose of the porcelain like you see on TeeZees plugs.

http://www.wallaceracing.com/plug-reading-lm.html

276173 276174
(http://www.wallaceracing.com/plug-reading-lm.html)

[TZ350]

.

NZ Cylinders trouble shooting page is worth a read. http://www.nzcylinders.com/Avoiding%20problems.html


Hi guys - actually its bloody obvious - when they say "under 30 dets in 3 laps" they mean it was 30 dets.
The Honda manual recomends 3 dets per Km MAX when ridden FULL OUT,tuned on the edge.
Thus to have 30 dets in 3 laps WHEN THEY SHOULD BE RUNNING THE NEWLY REBUILT TOP AND BOTTOM END IN, on part throttle, is simply irresponsible idiocy.
That many dets means it has WAY too much advance, or is WAY too lean on part throttle.
I have seen this before many times, on engines that are using the kit ignitions or the switchable ignitions that use lots of static advance on the stator.
They deto like hell when ridden slowly - as you do when running in, because so much extra advance is wound in down low to get good part throttle response when riding hard.
But whilst toodling round at part throttle, they will deto to self destruction in no time.
The deto counter is there to tell the rider something is wrong - to keep on shagging the engine with the deto counter rolling over in front of his eyes, when running in is just plain dumb.
Pull out some advance, lift the needle, and watch the deto counter, if it clicks over at all when running in - STOP.

[Frits Overmars]

NZ Cylinders trouble shooting page is worth a read. http://www.nzcylinders.com/Avoiding%20problems.html
Excellent site.

[TZ350]

343055
preparing the pistons. all grinded surfaces I polished smooth

Great work Peewee on your pistons. When I raced RD's we cut the bottom part of that central rib away. It inevitably broke off in the inlet port otherwise.

343053 TZ750 and a 343054 Vertex piston.

[peewee]

Great work Peewee on your pistons. When I raced RD's we cut the bottom part of that central rib away. It inevitably broke off in the inlet port otherwise.

343053 TZ750 and a 343054 Vertex piston.


these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

[katinas]

She should be happy about what happened to her number.

[TZ350]

these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

These are cast RD400 pistons, one has lost its tongue. The RD and TZ Yamaha's have wide inlets.

343059
Will you be Ok with forged pistons and the bridged inlet port? I don't know, sorry........ :scratch:

[TZ350]

.
Following on from Katinas last post.

343060

Eva Nugis of Latvia racing what looks like a 350cc IZH-54
great motorcycle blog here (https://t.umblr.com/redirect?z=http%3A%2F%2Fwww.thevintagent.blogspot. fr%2F2014%2F01%2Fanke-eve-goldman-soviet-racing-women.html&t=YjkyMmE1NGQ4YzE3MWI1NzNlNTBmZjA1NzMzZjZmNTdlMWVh Mzg0ZCw2Y0Z6akxuNA%3D%3D&b=t%3AGeRbgcVYn3ZgQ3LGzrn3xg&p=https%3A%2F%2Fgibier3000.tumblr.com%2Fpost%2F751 65339071%2Feva-nugis-of-latvia-racing-what-looks-like-a-350cc&m=1)

https://thevintagent.com/2017/07/02/anke-eve-goldmann-soviet-racing-women/

[oldjohnno]

these cyl have a center inlet bridge but i wasnt sure if i need to leave (for stability) or remove the middle finger of the piston skirt. pistons are wossner forged but i have no experience with them so i dont know how strong they are

I use Wossners because they are so light, significantly lighter than anything else I've tried. On the downside though the skirts are very thin and tend to collapse pretty quickly. I've never had one crack or break but they'll shrink quite a lot (0.2mm or so) after a couple of hours of high rpms/load.

[Pursang]

If you (or anyone else in this thread) ends up at Pikes Peak again, the beer (or other beverage of choice) is on me! I found exactly what I was looking for to fix my confusion re: carbs' circuits referred to mainly/only by throttle position and not engine speed.


Remember a carburetors air/fuel ratio at WOT becomes increasingly rich as the air flow through it increases with increasing rpm unless there is some sort of fuel correction. Anyway for what its worth, that is my take on it..........

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

[husaberg]

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

My understanding is this high speed over enrichment is only a factor with a correct or smaller than optimum carb.
AFAIK If its to big it will actually not auto enrichen.

[mantonakakis]

Got a chance to try out this idea of needle/needle jet controlling WOT mixture at low RPM. Surprise surprise, Wobbly and Frits seem to be onto something ;)

On my 50cc single-speed, I am using a 19mm PHBG, 32 pilot, about 2.5 turns out on the mixture screw, 260AU atomizer, 60 slide. Yesterday I used a W9 needle (2.5mm at the top, 1.4mm at the bottom, I think 20mm taper length, next-to-leanest clip setting). With a 69 main jet, I was a little too lean at WOT, especially once RPM got into the pipe's range. Never saw more than 450C EGT, ever.

Today I changed to a W11 needle, similar length and top diameter, but 1.8mm end diameter. One notch richer on the clip, and now 80 main jet. Low RPM WOT performance improved significantly, and EGT rose closer to a 500C minimum, with a solid 600C-650C while climbing a steady grade for a couple km at about 11k-12k (on the pipe - too rich at high RPM and couldn't rev much higher). Closing the throttle a little from WOT brought the EGT up a little bit and seemed to give more power - maybe a little leaner due to the needle. This was especially the case as RPM decreased, I think.

Anyway, vast improvement in low RPM performance thanks to this concept! Can't wait to keep tuning!

[peewee]

These are cast RD400 pistons, one has lost its tongue. The RD and TZ Yamaha's have wide inlets.

343059
Will you be Ok with forged pistons and the bridged inlet port? I don't know, sorry........ :scratch:

it probly wouldnt be a bad idea to do something with the center tang. what do you think of the red line on the photo ? im sure the thrust force will be less on the side tangs but maybe i could do something with them as well. most of the side tangs are protruding into the cyl window and not giving any support anyways. anything to make the engine hold together longer:laugh:

i wonder if your broken tang had anything to do with a smaller inside corner radius ? what length conrod were you using ?

also included is a paper of stress concentration which someone might find useful for making piston windows and cutouts

[peewee]

ok im a idiot. i think maybe most of the thrust force would happen around bdc when the piston is starting upward. in which case, the side tangs would be in full contact with the cyl wall below the windows. so i should probly leave the side tangs mostly intact

[F5 Dave]

So, is this the reason that carbs that are considerably larger than required, for fuel delivery purposes, can provide a top end performance gain?
At WOT, (or WFO, if you read Dirt Bike in the 70's) air velocity and vacuum actually falls and a degree of leaning off occurs.

Time to replace the old Amal 32 with a 36mm?

Cheers, Daryl.

Time to replace the old Amal with just about anything else carburetor or otherwise.

[peewee]

getting this shit box sorted. .44mm gaskets on both sides of the spacer looks to be just right. transfer bottoms are flush with piston top edge and theres a bit of material above the ports to play with as exh open 86atdc and trans 120. hopefully get some material this week and make the small bearing washers

[Pursang]

Time to replace the old Amal with just about anything else carburetor or otherwise.

Harsh! :blink:

[F5 Dave]

Do your period rules allow you to slip in a Keihin from a CR or something?

[Pursang]

Do your period rules allow you to slip in a Keihin from a CR or something?

Any period(ish) Roundslide is ok!

I wont even use a Keihin on my Honda...:bleh:

343080
SL100 with 28mm Amal Mk2

Cheers, Daryl.

[F5 Dave]

Forgive me. Indeed that fine steed deserves the best racing Amal (was wondering if spell check would improve on that) available.

[RAW]

Making the auxiliary ducts wider than 12mm made less power was my experience

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

[RAW]

Making the auxiliary ducts wider than 12mm made less power was my experience

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

[jamathi]

The 12mm wide
Are you indicating that the maximum width of a sub exhaust duct in the RSA is 12mm at its widest point within the duct ?
I have an aprilia APE cylinder with sub exhaust ducts measuring almost 14mm in width & 13.4mm in the vertical axis at its largest point within the duct

More than 12mm gave less power....

[JanBros]

back from the 10hour race in Laon, France. it was a

undetectable step for manking
giant leap for us


343100

1st in our category in only our second attempt :woohoo:

343116343117343118

it's all about teamwork, even in the pits :

343120

and perhaps the most important picture of the WE :

343119

my new suspension survived the race, the soft side worked flawless but it seemed as if the hard part didn't and we just bottomed out the soft part. But this picture says it all : the hard part was not way near hard enough .

Thx to everyone sharing their info on this great site, you're all a part of our victory :rockon:


edit : first effort at hosting pictures on kiwi biker, but seems I'm doing something wrong ? why are they only links and no pictures visible ?

[sispeed]

These are cast RD400 pistons, one has lost its tongue. The RD and TZ Yamaha's have wide inlets.

343059
Will you be Ok with forged pistons and the bridged inlet port? I don't know, sorry........ :scratch:

If this type of piston is used in a RD 400 there is no wonder that one lost its tongue. They are YPVS Water-cooled Style and there is a bridged Inlet. RD 400 don't have a bridge, so chances are good the tongue snaps at the lower port of the inlet.
If I use such pistons in Air-cooled Motors, without a bridge I remove the tongue before installing and using the pistons
Regards Siggi

[mantonakakis]

Still trying to understand why/how the needle/tube annular area sets the fueling at low RPM WOT, and main jet takes over once engine speed increases enough. I tried the trick of removing the main jet completely, with the biggest needle tip diameter available, and I just made a lot of smoke and stalled the engine. But with a main jet in place, changing the needle tip diameter and/or clip position does indeed seem to make a big impact at low RPM WOT.

Maybe in my case this is due to a relatively small main jet which ends up restricting the flow even at low RPM. I am using a 0.80mm main, 1.80mm needle tip, and 2.60mm atomizer tube. This gives a needle/atomizer tube annular area ~5.5x greater than main jet area at WOT (I would need ~1.87mm main to make them equal). With no main jet, I suppose this annular area is simply far too large for my 50cc engine?

In trying to get a better understanding of this, I went through the Dellorto manual again. For my PHBG, the bushing/nozzle/shroud has an air feed hole from the idle circuit air inlet. It seems this allows air to flow through the idle circuit inlet and around the OUTSIDE of the atomizer tube before entering the venturi. And I guess when air flow is low in the venturi and there is little vacuum (low speed WOT), the shroud should cause a pressure drop around the atomizer tube outlet that pulls air through the idle circuit inlet and fuel through the main jet and out the needle/tube annular area?

In the case of my 50cc engine, should I trim down the shroud as Wobbly mentioned here? (https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131108956#post1131108956)

https://cdn3.volusion.com/vod3d.s9orw/v/vspfiles/photos/dellorto-AU-bushing-0965500-3.jpg

343127

[wobbly]

The drilling from the very front of the bellmouth thru into the emulsion shroud well is referred to as the Main Air Corrector circuit.
In most carbs this is adjustable with a replaceable jet , but that Dellorto doesn't have this facility.
A bigger air corrector drilling reverses the tendency for the fuelling to become richer as air flow increases.
A similar effect is seen with the shroud height , as is detailed in the Dellorto manual - a lower shroud richens the mixture at lower rpm
and then leans off the fuel curve at higher rpm WOT.
Having an annulus area at WOT that is 5 times the main jet area indicates a real weird jet combination that can never be tuned
to have any effect on low rpm WOT jetting - exactly as you discovered.

[wobbly]

I to can confirm that there is an optimum duct size for the Aux ports.
There is a catch 22 involved,making them bigger may well increase Blowdown flow Cd but in doing so you are also
increasing the area change where the side duct intersects with the main Ex.
This then increases the duct volume - and as going smaller has been the route to big power increases , this isn't a good thing.
The only way to find out is to ruin a cylinder like I did , by gradually increasing the width until power drops.
The other variable is the bridge length - shorter is better.
Again I kept grinding them back toward the bore with a concave radius on the exit side.
I lost power ( and the bridge started to bulge inward against the piston ) when going smaller than ( again ) 12mm length.

[mantonakakis]

The drilling from the very front of the bellmouth thru into the emulsion shroud well is referred to as the Main Air Corrector circuit.
In most carbs this is adjustable with a replaceable jet , but that Dellorto doesn't have this facility.
A bigger air corrector drilling reverses the tendency for the fuelling to become richer as air flow increases.
A similar effect is seen with the shroud height , as is detailed in the Dellorto manual - a lower shroud richens the mixture at lower rpm
and then leans off the fuel curve at higher rpm WOT.
Having an annulus area at WOT that is 5 times the main jet area indicates a real weird jet combination that can never be tuned
to have any effect on low rpm WOT jetting - exactly as you discovered.

Thanks so much for the insight, Wobbly. I just checked the carb, and there are indeed two air passages at the mouth of it - one that feeds the idle and starter circuits, and one that solely feeds the shroud/bushing around the outside of the emulsion tube (the one on the lower right in the picture). The emulsion tube/atomizer is about 0.8mm smaller in outer diameter than the inner diameter of the shroud piece, and sure enough, spraying carb cleaner into that inlet resulted in a nice flow around the outside of the emulsion tube and into the throat of the carb, and then on into my eyes ;)

In my case, I guess the best option is to try making a fatter needle tip diameter? Or fill and drill the emulsion tube and decrease the diameter of the top of the needle.

https://i.imgur.com/yawtYCH.jpg
https://i.imgur.com/bIbfVBJ.jpg

[husaberg]

there are pages of stuff here (https://www.kiwibiker.co.nz/forums/album.php?albumid=4844) the carbs have overlapping fuel circuits so there are many ways to skin the cat or at least massacring its hairsyle where the only option is shaving its head.
In Cameron's Street bike book there is the best description of tuning from zero i have seen.
Bell has lots of detail in regards to old Mikuni stuff esp VM and Rbinsons is worth reading

[oktrg500]

.
Welcome Octrg500

These are some earlier posts I found using the Google "site:" search option.

Thanks very much, TZ350. As always, you're very helpful. I appreciate it very much. The reason why I'd like to learn as much as possible about reading the smoke ring is this will also benefit my other projects: A 70cc aircooled engine. which started it's life as a 50cc Minarelli engine. A couple of Aprilia RS125 streetbikes, which are my rolling laboratories. And the RG500 streetbike, which is not so streetable anymore due to getting good help from a Swedish company tuning the engine :banana:

[TZ350]

343134

Tim out peddling a Team ESE NSR110 around, number 77.

343133

What we are trying to do now is make sense of the tire wear.

Any comments based on https://lifeatlean.com/motorcycle-tyre-wear-guide/ would be welcome.

[TZ350]

.
A bit more on air correction jets.

343135


Just a small point TeeZee, the elongated oval formed around the main air corrector feed hole you will need to fit a thin wall sleeve in there, pointing directly out the bellmouth to a point where its not
affected by the venturi .
The idle air is going to be affcted as well but not as drastically.
If you dont, the air corrector orifice will be subject to increasing negative pressure as the velocity increases - exactly the opposite to what is needed to lean out the fuel curve
that naturally gets richer in any carb like this.


258280258281258282

OK, used a bit of 1/4" SS tube and linished it down to 6mm, spinning the job with a battery drill makes for a fairly round finish, cleared the end with a center drill, tapped a 13mm length into the carb, Job done. The hole next to it is plugged and I may smooth it off with glue sometime.

But now I guess I have to go back and check it on the dyno again.

I may be able to use a bigger mainjet now more air will be going through the air correction jet.

Bigger main jet should mean richer down low to mid for smoother drive at the lower end of the torqe curve and then drill the air correction jet out untill the top makes best power.

258284

On other sessions while testing different carbs the area between 8 and 9 K on the graph, the curve was much smother and sounded better on the dyno when it was richer there.

258285

The blue line was the IE carb I tried a while back, the jetting on one of the runs didn't make much power but it drove well in the 8-9K area.

I wonder if with a bit of playing with a bigger main jet and carefully drilling out the air correction jet I can get the red line to drive as smoothly.

[peewee]

I've had good results with steel washers as well. I machine them from some big socket head capscrews I have on hand, not super hard but very tough, grade 12.9 on the metric scale or around 170,000 psi in old speak. Once they're parted off I polish the sides on some fine wet and dry on a surface plate.

hey mate im going to try some 4130 alloy in .63mm thick. which will give me about .6mm axial play of the bearing and it should be fine i think. since the bearing cage is far wider that the rod width, the washers wont reduce any lube to the bearing so i dont think ill drill any lube holes in the rod like i first thought. and its a short run engine on methanol so i wont have to worry about extreme heat

[EdE]

If this type of piston is used in a RD 400 there is no wonder that one lost its tongue. They are YPVS Water-cooled Style and there is a bridged Inlet. RD 400 doesn't have a bridge, so chances are good the tongue will snap at the lower edge of the inlet.
If I use such pistons in Air-cooled Motors, without a bridge I remove the tongue before installing and using the pistons
Regards Siggi

RZ350/Banshee pistons in RD400s
My experience has been 99% RD250/350/400/Early TZ/RZ so I have rebuilt and modified just a mountain of these engines so of i've seen many many RZ350/Banshee pistons come out of 400’s (and of course installed a mountain of them). These pistons were a absolutely without a doubt a wonderful windfall for the RD400 but you all are right the center tongue which was designed for a bridged intake catches on the RD400’s single intake. Stock and of course even worse with a modified intake. Being aircooled cylinders using more clearance than the watercoolers doesn’t help the issue either. I’ve been called more than once to help someone determine what the noise is after they had some four stroke shop bore their cylinders and give them a set of pistons.. Pull a reedcage and there’s the tang (or tongue).. Of course the other problem is most non 2stroke experienced shops or even those with just modern 2 stroke experience only put what I call micro chamfers on their ports and that doesn’t help… (aircooled cylinders need more chamfer!!) Bottom line from experience and observing piston wear patterns that are always ½ way up to all the way up the “usual” 4-5mm tang when run for any length of time in a 400 if they aren't broken off.. Is cut the tang off and put a chamfer on the cutout it forms, DEFINITELY leave the side “tangs”, and always use a really nice radius and a generous chamfer on the bottom of 400 intakes. Ed

[flyincat]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

[AndreasL]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

Expert, in any way, I’m not. But...

I would say this is, or at least was, the norm.
In the old days of 125/250/500 it’s all quiet natural to do the development on a 125 “dummy case” or engine.
Jan Thiel, jamathi, have told how all the Aprillia cylinders was developed on a single RSW case, even if the RSA was rather different, since they also had to fit the 250. Hope I got that right.
In the 60-70:s BMW i.e. developed new 16v heads for F2 on a single that was a cut off from the inline 4 it was destined for. Google Apfelbeck, who was the brains behind it as well as the patent holder, and prepare for a real “valve chock”. :msn-wink: Successful though. :niceone:

[RAW]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

Don’t cut it in half, just remove the items that are not required if you were to run the engine with one working cylinder only.
Depending upon the engine type & configuration you may need to rebalance the crank for a single cylinder use.

[41juergen]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

I have a TZR250 3XV (the V type) and have modified a TZR125 4FL to fit all the 3XV (or 4DP TZ type) parts as best as I can. Of course the crank housing and the crank itself is a bit different, but that's the compromise for me...
Welcome Ed, world is small... :2thumbsup

[katinas]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

This is indeed very helpful for development and mistakes friendly configuration. Still testing things on both Honda NS 250/2 and Suzuki RGV 250/2 with modified cranks for single cylinder. Both V 90 engines, but on NS 250 horizontal cylinder near primary drive and RGV 250 vertical cylinder at ignition side ( add photo). Mainly it depends on which shaft is easier to make.
On parallel twin end result would be more accurate, but with V engines is some mismatch (different cylinder position, crankcase volume, ex pipes).

[flyincat]

Thank you, all, for the helpful tips and pictures!

katinas - What is with the large aluminum sleeve in the blank cylinder in the last picture?

For a parallel twin, are there any balance related tripping hazards with replacing rod/counterbalance with a plain shaft? I know squat about balance but it seems balance in a parallel twin would be independent of the neighbor cylinder. Correct?

[rtechracing]

I posted my issues on this site hopeing to get some good feedback. Instead it ends up with a big argue regarding what Luc has claimed or said in the past. Why bother, instead lets spend our time and energy on a good discussion sharing information and knowledge about the fantastic art of 2-stroke.
Let`s agree on that we don`t have to share the same filosophy, some thinks one thing is the right way to go and someone else thinks another route is better.....if someone claims he can make 100HP from a 50cc engine so what! let him think that.
Can some of you guys that keeps asking questions about what Luc have said or claimed give me a good theory why the power drops before entering powerband like the dynograph shows?

Thanks a lot guys!!

I just wanted to update you guys on the issue I experienced with the H2 engine previously discussed. Luc had the oportunity to help me and after performing changes according to Luc`s calculations the engine have never been more powerful. We have made a new PB in top speed and ET and is currently second fastest bike in europe with this type of bike. There is still more to come from this engine and it has been a privilege to work with Luc so far and I look forward to future colaboration as well

[TZ350]

...lets spend our time and energy on a good discussion sharing information and knowledge about the fantastic art of 2-stroke. Can some of you guys give me a good theory why the power drops before entering powerband like the dynograph shows? Thanks a lot guys!!

I would love to know more about that common torque dip and learn more about your technique to improve it.


We have made a new PB in top speed and ET and is currently second fastest bike in Europe with this type of bike. There is still more to come from this engine and it has been a privilege to work with Luc so far and I look forward to future collaboration as well

Your success is great news. Can you share some more about the recent development of your bike.

[rtechracing]

I would love to know more about that common torque dip and learn some techniques that could improve it.
The torque dip is still there but flatter and way higher then before as it enters powerband and the overall graph is stronger than our all time high dyno reading.


Your success is great news. Can you share some more about the recent development of your bike.
Sorry, I am not allowed by the owner of the bike to share anything, I hope you respect that.

[rtechracing]

I would love to know more about that common torque dip and learn more about your technique to improve it.



Your success is great news. Can you share some more about the recent development of your bike.

The torque dip is still there but much flatter and way stronger as it enters powerband. The overall graph is stronger all the way and peaks higher than our all time high dyno reading.

[TZ350]

Sorry, I am not allowed by the owner of the bike to share anything, I hope you respect that.

I can understand it but don't respect it, taking from the table without contributing in return, would you respect that?

[wobbly]

Ha ha , we bitched about Luc because ( among other things ) we never got one useful piece of actual hard info .
Now you come on here singing his praises - and funny that , no info about the project.
So the point of telling us about this is ?
But you want us to help you - which we can as a group tell you all about the power band dip , its common knowledge.
Get real.

[peewee]

I can understand it but don't respect it, taking from the table without contributing in return, would you respect that?

what do you expect when site rules allow any rube to wander through and copy photos and take info

[Pursang]

what do you expect when site rules allow any rube to wander through and copy photos and take info

Hey!! Fair go! I resemble that remark!:wari:
.
.
343167 Copy and take this! :p

[katinas]

Thank you, all, for the helpful tips and pictures!

katinas - What is with the large aluminum sleeve in the blank cylinder in the last picture?



Sleeve on RGV just separate oil for bearings, from blanked cylinder crank space.
On NS, just put same oil in vertical blanked cylinder crank space and covered with plate instead of a cylinder. It could be usable for parallel twin too.

[F5 Dave]

So, are they like a tapered gas fitting thread?

[Pursang]

So, are they like a tapered gas fitting thread?;)

Do Not 'Dis' this Product of my Extensive Knowledge & Experience:
Fully Reverse Engineered, Anti-Anti Reversion Step-Tapered Header Pipe. Multi Championship Winner!! :first:
Universal application, adaptable to 2T & 4T. Tuned/Un-tuned length is fully micrometer adjustable.
Corrosion Resistant, Galvanised finish. Easy & Quick Home assembly and fitment with basic Tools & Technical Knowledge.
Order NOW! They're going FAST!! Contact ME NOW, or check my facebook for Full details!
Ok, Sure, NOT any Real details, just some Old accomplishments, you must be a Friend and Subscribe and sing My praises and send Real money to Me for Anything!

Rube...:banana:

[katinas]

Magic artwork photo

[speedpro]

Not going to mention any names but I find it hard to believe that the 2-stroke world is not totally dominated by his work.

[wobbly]

It is SpeedPro - just like the KZ kart class championship being raced in Lonato as we speak - its dominated by his finest creation , the Ryger.
Oh , no sorry , it will be - soon , very soon.
And dyno sheets will be produced to prove it - soon , very soon.
Ye of little faith.

[jamathi]

Dear multi-cylinder experts,
When doing cylinder development on a multi-cylinder engine, is it common to make a single cylinder development engine? For example, could a guy cut a parallel twin in half? Obviously on a water cooled, it would take some plumbing work. The crankshaft would need some major mods. Just curious if anyone goes through the hassle. Thanks!

I always did this, it is the only right way!

[husaberg]

I always did this, it is the only right way!

I have always heard them refered to as being test mules, i am not sure if that translates to Dutch or Italian.
343170

[fpayart]

Hello Jan,

I did not pay enough attention to this picture of the Aprilia single-cylinder.
I discover the device at the bottom of the chart disk.
Curious, is not it!
What was the function? Measuring sensor or signal for ignition?
I seem to see that in the lower part of the disc, the notching is irregular?

343176

Friendly
Francis

[jamathi]

Hello Jan,

I did not pay enough attention to this picture of the Aprilia single-cylinder.
I discover the device at the bottom of the chart disk.
Curious, is not it!
What was the function? Measuring sensor or signal for ignition?
I seem to see that in the lower part of the disc, the notching is irregular?

343176

Friendly
Francis

it was used for flow testing.
From the flow testing the idea of the RSA was born.

[TZ350]

343179 343178

Pinky is going to get a new heart.

A Suzuki GP100 fits in there real nice and with the NSR110 conversion it should be good for 30hp and water cooled for all day power.

Those Team GPR frames are real light and beautifully made.

[peewee]

does anybody know about these conrods ? https://www.ebay.com/itm/Yamaha-RD350-RD-350-RD250-RD-250-AIR-COOLED-Conrod-kit-Con-rod/122549493543?_trkparms=aid%3D1110001%26algo%3DSPLI CE.SIM%26ao%3D1%26asc%3D20131231084308%26meid%3Dd7 e2c5944a674cbfb8d1f5652c19c4f5%26pid%3D100010%26rk %3D2%26rkt%3D12%26sd%3D292342614514%26itm%3D122549 493543%26pmt%3D0%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100010.m2109

[F5 Dave]

343179 343178

Pinky is going to get a new heart.

A Suzuki GP100 fits in there real nice and with the NSR110 conversion it should be good for 30hp and water cooled for all day power.

Those Team GPR frames are real light and beautifully made.
Nice, rid thee of thy foulstroke Gubbins.

I only rode the TZR one Brent had, but it was clearly a better chassis than my NF4. Mind you it would have cost more than the $300 I effectively paid.

[husaberg]

does anybody know about these conrods ? https://www.ebay.com/itm/Yamaha-RD350-RD-350-RD250-RD-250-AIR-COOLED-Conrod-kit-Con-rod/122549493543?_trkparms=aid%3D1110001%26algo%3DSPLI CE.SIM%26ao%3D1%26asc%3D20131231084308%26meid%3Dd7 e2c5944a674cbfb8d1f5652c19c4f5%26pid%3D100010%26rk %3D2%26rkt%3D12%26sd%3D292342614514%26itm%3D122549 493543%26pmt%3D0%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100010.m2109

They are re branded Long brand rods
I remember someone not being happy with some... Mike?
but it might have been more to do with the bearing?

[wobbly]

No silver coating on the old ( useless ) M style cage - cheap junk.

[lucf]

I just wanted to update you guys on the issue I experienced with the H2 engine previously discussed. Luc had the oportunity to help me and after performing changes according to Luc`s calculations the engine have never been more powerful. We have made a new PB in top speed and ET and is currently second fastest bike in europe with this type of bike. There is still more to come from this engine and it has been a privilege to work with Luc so far and I look forward to future colaboration as well


I can understand it but don't respect it, taking from the table without contributing in return, would you respect that?


Ha ha , we bitched about Luc because ( among other things ) we never got one useful piece of actual hard info .
Now you come on here singing his praises - and funny that , no info about the project.
So the point of telling us about this is ?
But you want us to help you - which we can as a group tell you all about the power band dip , its common knowledge.
Get real.


rtechracing,
If you don't get the right information, I'm ready to make the right calculation for you.
Which will show exactly what is wrong, but only directly and without any information to this forum.

Everyone was free to help him !

[TZ350]

343180 very good big end brg.

Rod kits with this style of flat big end bearing are much better than the old copper coated W bearing which tends to break up.

343181 not so good big end brg.

[husaberg]

does anybody know about these conrods ? https://www.ebay.com/itm/Yamaha-RD350-RD-350-RD250-RD-250-AIR-COOLED-Conrod-kit-Con-rod/122549493543?_trkparms=aid%3D1110001%26algo%3DSPLI CE.SIM%26ao%3D1%26asc%3D20131231084308%26meid%3Dd7 e2c5944a674cbfb8d1f5652c19c4f5%26pid%3D100010%26rk %3D2%26rkt%3D12%26sd%3D292342614514%26itm%3D122549 493543%26pmt%3D0%26noa%3D1%26pg%3D2047675&_trksid=p2047675.c100010.m2109
.................



Yeah and as Mike says I built a crank with Long brand rod. Not a good ending. Bit like the picture Mike uses for his avatar.

[speedpro]

I saw the "L" on the rod and immediately thought "Long" brand, and F5 of course.

[husaberg]

I saw the "L" on the rod and immediately thought "Long" brand, and F5 of course.
I dug out a ac cr80 Clutch cover the oher day turns out they bolt onto a MB for those that wanted to delete the oilpump balancer set up to fia RS frame.

I also found the FZR250 rocker cover i swore i never had, that was for the Grumph engine..


What I have learnt is Long brand rod kits used to have crap bearings in them. I'd buy genuine MB50 bearings (if they are the same for yours) as I seem to remember they got superceeded by the CR part, but that now listed as MB part is super legal.
One of the Honda Leads runs the MB/CR big ed as well. either the 100 or 80SS


With no money for new parts the cycle repeated till I finally rebuilt my now fast engine with a new aftermarket Long brand rodkit. I'd won my first race mostly by luck and speed. Rod snapped. New std parts and it never did it again. Now other parts broke. I spent so much time chasing my tail I never had time to learn to ride.
The RG changed all that but heck I was in my mid twenties by then.
Sheesh.

[jato]

They are re branded Long brand rods
I remember someone not being happy with some... Mike?
but it might have been more to do with the bearing?

Years ago i remember someone wandering around the "Powder Keg" hotel in Ohakune , half a beer in one hand and half a con-rod in the other telling a sorrow filled story about Long rods... i think he ended up a sad drunk

[husaberg]

Years ago i remember someone wandering around the "Powder Keg" hotel in Ohakune , half a beer in one hand and half a con-rod in the other telling a sorrow filled story about Long rods... i think he ended up a sad drunk

Probably ended up spitting out diced carrots. He did well to walk after a broken rod.

[teriks]

rtechracing,
If you don't get the right information, I'm ready to make the right calculation for you.
Which will show exactly what is wrong, but only directly and without any information to this forum.

Everyone was free to help him !

Not sure why I'm wasting time and forum space writing this, but anyway.
Why the h-- spend time on a forum intended for sharing knowledge and ideas with such attitude?
Nothing good will come out of that for anyone, and certainty not for you lucf.

[F5 Dave]

Years ago i remember someone wandering around the "Powder Keg" hotel in Ohakune , half a beer in one hand and half a con-rod in the other telling a sorrow filled story about Long rods... i think he ended up a sad drunk
Well if it was me, I resent that. I'm not Sad.

But mine broke in Palmy and the bike shop I bought it from was given it to show the distributor.

[RomeuPT]

Hello

Long time not posting.

Sadly the shinning kz kart pistons don't fit the honda T-Port shape. Leaving small entrances from cranckcase to the exhaust port at TDC..

one more piece for the shelf

Cheers

343183

[Brett S]

Hello

Long time not posting.

Sadly the shinning kz kart pistons don't fit the honda T-Port shape. Leaving small entrances from cranckcase to the exhaust port at TDC..

one more piece for the shelf

Cheers

343183


Depending on which KZ piston you tried, there may be one that has a larger radius to keep the exhaust covered.
Last year Meteor released a TM KZ 10C piston that had the larger radius as shown in the pic. Casting 2630 (117gm) on top/left of original style 2311.
They also have a flat top version the TM factory team was using in 2018 as well with the larger radius.

[RomeuPT]

Depending on which KZ piston you tried, there may be one that has a larger radius to keep the exhaust covered.
Last year Meteor released a TM KZ 10C piston that had the larger radius as shown in the pic. Casting 2630 (117gm) on top/left of original style 2311.
They also have a flat top version the TM factory team was using in 2018 as well with the larger radius.

Hi.

Thanks.

This is actually a Iame piston because I need the 29,50mm height!

I will contact the dealer if they have this version for IAME

[DoldGuy]

Hi.

Thanks.

This is actually a Iame piston because I need the 29,50mm height!

I will contact the dealer if they have this version for IAME

Don’t know if this helps but:

Kawasaki 1994 KX125 Flat Top Piston has a 29.5 Compression Height & a 15mm Pin

1993 KX125 Flat Top Piston has a 29mm Compression Height & a 16 mm Pin.

[AndreasL]

Maybe (most likely) posted before, but what the...
Up here in the north it starts to get dark and cold so everything easing the pain is welcomed.

Ones again I’m amazed by the Jamathi-story and the complete sacrifice and devotion...and all the success and know how accumulated. And now shared with us through sites like Kiwibiker! ��

http://www.classic50racingclub.co.uk/mount-up---the-bikes.html

[katinas]

Eric Offenstadt NSR 500V


https://www.mcnews.com.au/honda-nsr500v-eric-offenstadt/

[TZ350]

Eric Offenstadt NSR 500V https://www.mcnews.com.au/honda-nsr500v-eric-offenstadt/

That is a very interesting bike. I particularly like the chain idler pulley. AS well as neutralizing some of the chain pull effects on suspension geometry. It looks a great way to stop the chain dragging on the swing-arm. I am going to copy the idea for my bike as the chain is slowly cutting its way through the swing-arm pivot on my beast.

343191 https://www.mcnews.com.au/honda-nsr500v-eric-offenstadt/

[husaberg]

That is a very interesting bike. I particularly like the chain idler pulley. AS well as neutralizing some of the chain pull effects on suspension geometry. It looks a great way to stop the chain dragging on the swing-arm. I am going to copy the idea for my bike as the chain is slowly cutting its way through the swing-arm pivot on my beast.

343191 https://www.mcnews.com.au/honda-nsr500v-eric-offenstadt/

ATK used to do it with two small sprockets one top one bottom.
https://motocrossactionmag.com/the-real-story-of-americas-most-famous-dirt-bike-designer-horst-leitner/
343192343193343194

[Michael Moore]

The large idler wheel will give a lower RPM at the bearing than the small wheels/sprockets, but it is more difficult to fit in an often crowded space. An idler that locates the bottom run of the chain can adjust the reaction to the lower forces on the over-run.

[F5 Dave]

My understanding is that will absorb a decent amount of power, if it gets warm you'll know, but try it on the dyno.

[JanBros]

I particularly like the chain idler pulley. AS well as neutralizing some of the chain pull effects on suspension geometry.

you also lose the benefits of the chain-effect. there is a reason not a single racing motorcycle uses this ;-)

[Michael Moore]

You can also have too much chain effect which is one reason why so many powerful race bikes have adjustable swing arm pivots. In addition, it may be that they are not so much trying to increase/reduce the chain effects, but to reduce the amount of variation in them in the working area of the rear suspension so the suspension can work smoothly based on contact patch loads and not the chain jerking things around.

Chris Cosentino has used dual idlers to control chain forces on his Rotacular singles and had them as a design feature on his Moto2 project (thanks for killing that FIM with the "no prototypes" rule):

http://www.eurospares.com/graphics/chassis/Cosentino/Rotacularsingleiso2.jpg

[Pursang]

Countershaft sprocket is nice and close to swingarm pivot. :clap:

C/S is inline with S/A pivot or slightly above. :no:
This can cause chain to contact the bottom of the Swing arm, during suspension compression.

C/S sprocket is about as small (13T) as would generally be recommended.:(
A larger sprocket would provide more S/A clearance, but require correspondingly larger rear sprocket to maintain ratio.
(More chain length, more mass, more inertia and more unsprung weight.) :apumpin:
Idler, as positioned, keeps chain further away from S/A than it would be without one.;)

Idler is significantly behind S/A pivot, and located on the frame, not on S/A, so does not really try to eliminate chain length variation through the suspension travel.:whistle:
Hence, spring loaded chain tensioner, fitted on bottom of S/A.:nya:

Idler is 'sort of' in line with lower pivot point of suspension unit and might also be intended to direct squat/anti-squat chain forces to the line of action of the rear suspension.:scratch:
Is this a good thing? Too many unknowns and variables for me to know.:weird:

But I give 1 point to the builder, for trying something outside the box.:niceone:

Cheers, Daryl

[TZ350]

But I give 1 point to the builder, for trying something outside the box.:niceone:


Totally agree, ....... https://www.kiwibiker.co.nz/forums/images/smilies/thumbsup.gif for trying something outside the box.

[pete376403]

BMW G450X had the countershaft sprocket centre in line with the swingarm pivot, so chain tension remained constant and to reduce chain effect on the rear suspension

[diesel pig]

BMW G450X had the countershaft sprocket centre in line with the swingarm pivot, so chain tension remained constant and to reduce chain effect on the rear suspension

Which is the gimmick Bimota used in the 1970's but had forgot about by the 1990's.

[andreas]

Old gold Blair. He says 23* spark advance is optimum. How would a kart 250 single spark graph look, like 19* at peak torque?

[OopsClunkThud]

Have a scavenging balance question. Is there a recommended target or range for the 'radial scavenging direction resultant'?
Clearly it's bad if it's greater than 90°, but is 90° the target or is it better to keep the resultant leaning away from the exhaust to keep it attached to the back wall?

Cylinder I'm starting with has a resultant of 73°

I understand this method is only a guidance and starting point, but that's where I'm at with this cylinder.

[Frits Overmars]

Have a scavenging balance question. Is there a recommended target or range for the 'radial scavenging direction resultant'? Clearly it's bad if it's greater than 90°, but is 90° the target or is it better to keep the resultant leaning away from the exhaust to keep it attached to the back wall? Cylinder I'm starting with has a resultant of 73°.
I understand this method is only a guidance and starting point, but that's where I'm at with this cylinder.With a radial scavenging direction resultant of 73° the scavenging column is leaning away from the exhaust, which in itself is a good thing: no losses.
But if you wish to maximize the transfer area, you'll also need ports more or less opposite the exhaust port, which will make the scavenging column lean towards the exhaust. A little leaning can be tolerated as a compromise (more area and more losses), but do not go too far past 100°.

[Frits Overmars]

Old gold Blair. He says 23* spark advance is optimum.Blair wrote that this value was for a designed BMEP of 105 psi, or 7,24 bar in real money. That was some time ago, in 1971.
The Aprilia RSA, a somewhat younger engine (2005), has a BMEP of more than double that, at 16° spark advance. Take your pick.

[wobbly]

Blairs 500 single was hamstrung by super conservative design elements.
A square Exhaust port - parallel header - 120mm skinny pipe etc.
This then results in very low dynamic compression, and with the low bmep generated , peak combustion efficiency was only gained with a ton of advance.
Modern race engines generate double the bmep , and all end up needing around 15* advance at peak power.

[andreas]

All right, imagine how the wrong conclusions appear. Thanks Frits and Wobbly.

[RomeuPT]

Depending on which KZ piston you tried, there may be one that has a larger radius to keep the exhaust covered.
Last year Meteor released a TM KZ 10C piston that had the larger radius as shown in the pic. Casting 2630 (117gm) on top/left of original style 2311.
They also have a flat top version the TM factory team was using in 2018 as well with the larger radius.

Mondokart don't reply to emails :/

is this the one with larger radius too (2641)?

https://www.mondokart.com/en/meteor-pistons-mondokart/pistons-for-tm-kz-mondokart/piston-tm-kz-r1-ring-07-mm-flat-sky-zero-degreesi-exclusive-news.html

[Brett S]

Mondokart don't reply to emails :/

is this the one with larger radius too (2641)?

https://www.mondokart.com/en/meteor-pistons-mondokart/pistons-for-tm-kz-mondokart/piston-tm-kz-r1-ring-07-mm-flat-sky-zero-degreesi-exclusive-news.html

That looks to be an exclusive (2702) to Mondokart with the 0.7mm ring.
I believe the 2641 has the same skirt cutout as the 2630 but cast with alowance for the flat top and is the light weight model to the 2630.
Without seeing one the, 2677 is the light weight, flat top with 0.8mm ring that might either be the same casting as the 2641 or the mondokart 2702 or they are all the same casting, i'm not sure.

[Frits Overmars]

Blairs 500 single was hamstrung by super conservative design elements. A square Exhaust port - parallel header - 120mm skinny pipe etc. This then results in very low dynamic compression, and with the low bmep generated , peak combustion efficiency was only gained with a ton of advance.
Modern race engines generate double the bmep , and all end up needing around 15* advance at peak power.Yep. The RSA has 16° ignition advance at 12.500 rpm (maximum BMEP and maximum torque) and 15° at 13.000 rpm (maximum power).

[Tim Ey]

Yep. The RSA has 16° ignition advance at 12.500 rpm (maximum BMEP and maximum torque) and 15° at 13.000 rpm (maximum power).

Talkin' RSA Power: Why did I never see a correction factor and air pressure & temperature on the power diagrams?
At which ambient conditions was the RSA investigated/developed?

[Frits Overmars]

Talkin' RSA Power: Why did I never see a correction factor and air pressure & temperature on the power diagrams? At which ambient conditions was the RSA investigated/developed?There is a whole lot more than just air pressure and temperature that does not show on the power graphs Tim. All it would take is one push at a button on the dyno computer and you would see something like this:

DRVE3452.PC:
2006-10-25; N°curva 3452 moto DRVE n°03/06
Albero Drd 01/05 C004 raf.sp10.1bilan; biella Drd 120mm n°13 C004;
cuscinettiRulli Apr.giocco 0.057 C004; pistone 2544 (961) C04;
testa AC 56-G std TR0.75-0.76 C36; cilindro APE341 54.011;
valvola scarico/condotto sup.C004 Inf.C004 molle C004; tubo 69/03 moto Protti ferro;
Colettore/termin/silenz: 38.7 +0m+1gr.Sil.Dlr Hrc-std; mappatura GP184+0%A0
98B-V020B-P083B; candela Denso 35 usata C036; accensione Poker; Carburatore Vhta 41
Moto n°7 new valvolina; carburazione AU248T1.5P265Max218m48-4f-P120;
benzina ELF olio ELF 909 4%; alimentazione 155°/89.5° as20°r0sc25°r10C004

But that would really clutter up the graphs, wouldn't it?

By the way: the dyno rooms, pictured below, were climatized, so temperature, pressure and even humidity were pretty constant.
343216 343217 343218 343219

[Haufen]

There is a whole lot more than just air pressure and temperature that does not show on the power graphs Tim.

I think he's got a point there. Nowadays, a dyno chart showing power without a reference under which ambient conditions this power was measured and by which formulas the power was corrected (eg. DIN 70020..) and where it was measured (e.g. engin, rear wheel etc.) is totally worthless.




By the way: the dyno rooms, pictured below, were climatized, so temperature, pressure and even humidity were pretty constant.
Of course they were, but I do not see a reference to this in your last post. What was the temperature of the intake air? What was the cabin pressure? By which formulas was the power corrected? What kind of power are we looking at? Has it been corrected at all?




But that would really clutter up the graphs, wouldn't it?


Not at all! A documentation like this (plus ambient conditions and test conditions (e.g. typre pressure, tyre type etc) is pure gold for everyone making dyno runs on a more or less regular basis and trying to get the max our of it. Be it for finding problems on the engine or understanding which direction to head to for more power. One could put it on a second page though.

Was that the data which belonged to the 54hp graph Tim was referring to? Or just a random one? Can you help us 'decipher' it?

[Frits Overmars]

Tyre pressure? Tyre type? Haufen, you do not seriously think that you can develop an engine to the required level by measuring rear wheel power, do you?
Tyre rolling losses are dependent on tyre deformation which is dependent on tyre pressure; those rolling losses heat up the tyre, which changes its pressure and the rolling resistance during the dyno run. Need I go on?

The RSA power was measured at the gearbox exit shaft, as has been mentioned repeatedly. The data-example I posted above is not from a 54 hp dyno run but from a different run, which by the way was not far short of 54 hp either.
I do not intend to start a language course of Italian technical abbreviations here, but anyone with a bit of two-stroke background should be able to deduce by the numbers what they are referring to.

The ambient factors were 27°C and 1013 mbar. Initially the ambient temperature was kept at the standardized 20°C, but in order to bring the circumstances more in line with the average circuit conditions it was later raised to 27°C. And because of the constant ambient factors there was no further correction required.
Anyway, most correcting algorithms are useless if not downright misleading when high-performance two-strokes are involved.

[TZ350]

343222

Aprilia's climate controlled dyno rooms are pretty impressive. And the sort of thing you need for professional engine development.

It is pretty obvious that they applied good scientific method in the development of the Race bikes, you would have to have a few screws lose to think or suggest otherwise.

343221 343223 50cc 2T

Team ESE's dyno is just an old Dynojet plonked in the corner of the work shop but we do Ok with it.

Our environmental control amounts to an exhaust fume extractor so we don't choke ourselves on smog.

Sure, we are not so scientific and measure at the back wheel but still make good progress.

The old Dynojet pretty quickly lets you know if your latest idea was a success or complete dud.

The ratio of success's to duds is about 55/45 so far. We make progress slowly but get there in the end.

The Dynojet is a great comparative tool.

343220 343224

Mike was pretty happy recording a 30hp run from his EFI Turbo 4T 100.

Was it 30,34hp SAE or 30,5hp DIN who cares. Just eliminate the variables like tire pressure the best you can and test it the same way each time and let the comparative results guide you.

[Frits Overmars]

I'm sure you Team ESE guys have more fun and less stress than the Aprilia racing department staff :2thumbsup

[Haufen]

Tyre pressure? Tyre type? Haufen, you do not seriously think that you can develop an engine to the required level by measuring rear wheel power, do you?
Tyre rolling losses are dependent on tyre deformation which is dependent on tyre pressure; those rolling losses heat up the tyre, which changes its pressure. Need I go on?

I am well aware. I wrote that passage regarding the tyres for the community to benefit from, as I figured the most common dyno type people reading here have acces to is an acceleration dyno just as Team ESE's dynojet.

What do you mean with required level?

Btw (this is again for anyone who is interested), there are good and worse tyres for dynoing. A good tyre for dynoing does not change circumference (by much) during high speed pulls and gives constant and repeatable readings once you start with a high enough pressure (higher than on the road in most cases). There may be differences in hp readings between tyres, even if both tyres can be categorized as 'good' by the definition above.



The RSA power was measured at the gearbox exit shaft, as has been mentioned repeatedly. The data-example I posted above is not from the 54 hp dyno run but from a different run, which by the way was not far short of 54 hp either.

I do not intend to start a language course of Italian technical abbreviations here, but anyone with a bit of two-stroke background should be able to deduce by the numbers what they are referring to.

The ambient factors were 27° and 1013 mbar. Initially the ambient temperature was kept at the standardized 20° C, but in order to bring the circumstances more in line with the average circuit conditions it was later raised to 27°. And because of the constant ambient factors there was no further correction required.
Anyway, most correcting algorithms are useless if not downright misleading when high-performance two-strokes are involved.

Come on Frits, you of all people should be well aware of the sensitivity of the high-performance two-stroke engine to air temperature, air pressure, humidity and when we're at it: water temperature (and EGT). Yet you draw a graph with your name on it containing none of the information just mentioned and when legitimately asked for the missing pieces, you post other information. That info was nice, thank you. But when we ask for temperatures and pressures, we don't care if the rod's name was Giovanna or if the head was the third from the right in the batch from april.

By the way, I am quite sure that - in contrast to the temperature - cabin pressure was not held constant at 1013mbar by the test cell for all the tests. The facilities capable of such a thing are quite expensive and as Jan mentioned elsewhere that he was rejetting on the dyno (there would be no need if everything was held constant), not given an acceleration dyno which he desired and that he did not use indication or a fuel metering device or exhaust gas analysis, (all valuable tools much cheaper than such a test cell) this would be highly unlikely. Also, using such a test cell - let alone several of these - just to keep the pressure at 1013mbar would be a waste of resources, as you could develop dedicated setups for e.g. higher altitude race tracks etc.

This leaves us with two options:
a) power was corrected and it is not known how as it came out already corrected (on the dyno computer screen there may have been two different hp values or at least the values during the measurement were not exactly the same as after post-processing). Or

b)there was indeed no power correction used, in which the repeatability from e.g. Friday to Monday (on a weekend nobody worked, if such a thing exists in motorsports) may be well off by a couple of percent. Let's say +10mbar from 1013mbar on Friday and -10mbar on Monday and we have found or gained a whole horse in 54. That is not really the precision one would prefer to have in one's tools, is it?

If I had to guess I'd vote for option a), and as we do not know by which factors or norm this was corrected, 54hp (measured) @ 1013mbar and 27°C, disregarding humidity, can be anything between 52,7 (SAE) and 54,6hp (Din). Or if it was PS (CV, metric hp) and not hp in Frits' chart, then between 52,1 and 53,9 hp.

The other way round, 54ps corrected by SAE would mean between 55,6ps (DIN) and 54ps corrected by DIN would mean 51,8ps (SAE) (=54,8 and 51 in hp).

So, depending on the method of measuring, the peak power of the Aprilia RSA is somewhere between 55,6 and 51,8 ps (or 54,8 and 51hp). I had hoped we would be able to get a much clearer picture after Tim's question.

[Frits Overmars]

What do you mean with required level?The level to be the best world-wide. What else?


I am quite sure that - in contrast to the temperature - cabin pressure was not held constant at 1013mbar Controlling the cabin pressure is about the simplest thing in a test cell, much easier and less energy-consuming than controlling the temperature, let alone the humidity. There are blowers pushing air in and ventilators sucking it out again. A simple set of louvres is all you need to balance in- and outflow and control the pressure.


you of all people should be well aware of the sensitivity of the high-performance two-stroke engine to air temperature, air pressure, humidity and when we're at it: water temperature (and EGT). Yet you draw a graph with your name on it containing none of the information just mentioned and when legitimately asked for the missing pieces, you post other information. That info was nice, thank you. But when we ask for temperatures and pressures....Which part of '27°C and 1013 mbar' didn't you understand?
Besides, I didn't realize that I was under an obligation to answer questions. In fact I didn't even know I was obliged to post anything.

[TZ350]

Come on Frits, you of all people should be well aware of the sensitivity of the high-performance two-stroke engine to air temperature, air pressure, humidity and when we're at it: water temperature (and EGT).

It is pretty obvious from their success that Aprilia were knowledgeable and careful operators, so your point is exactly? .... :scratch:

[wobbly]

Quote " By the way, I am quite sure that - in contrast to the temperature - cabin pressure was not held constant at 1013mbar by the test cell for all the tests. The facilities capable of such a thing are quite expensive and as Jan mentioned elsewhere that he was rejetting on the dyno (there would be no need if everything was held constant). " End quote.
OK - two statements couched as facts that are completely erroneous.

Firstly - ambient temp and pressure in a cell are easy and cheap to control.
At BSL we controlled the pressure by simply louvering the inlet and outlet fans by hand just before a test.
The temp was heated if needed by an inline burner , thermo controlled from within the cell.
My standard temp was 25*C and the incoming air was very rarely above this in mid summer , so cooling wasnt needed.
Humidity was deemed "too hard " to control without huge expenditure .But after checking the various correction standards we discovered that the Superflow dyno software predicted very accurately the needed
correction factor when the humidity changed.
The " real " corrected power was all but identical within the normal range of 25 to 75% here in NZ.

Second - yes Jan re-jetted on the dyno.
This had nothing to do with the ambient conditions , although that IS of course needed if the cell isnt controlled like it was at Aprilia.
The re-jetting regime was instituted to standardize testing , initially of pipes.
But since then I have found that virtually every small change made to a very high bmep race engine will result in a change in the final egt at peak power - skewing the results
to show power changes created by differing pipe temp, not the change created by the new setup.
Thus ever since Jan told me about this I religiously ensure every test run ends at 620*C , if not I rejet and rerun.
Same for water temp - every run starts at 40*C and my cooling setup is good enough to hold temp below 45* for the 3 pulls needed to achieve accurate averaging.

[husaberg]

Maybe you always need to look over your shoulder.
To see who is following behind.
343226
I think this pic is from the Garelli period?
We are lucky for the input we get here from some very knowledgeable and respected 2 stroke experts, Like the bloke above and others.
So if you take the time to ask a question of the people who contribute their knowledge so freely on here on the thread.
Respect their time taken to answer it, by reading their answers properly.
Also consider it's not a interrogation, no ones obliged to answer.

[Michael Moore]

Our environmental control amounts to an exhaust fume extractor so we don't choke ourselves on smog.

But that means you miss out on the fun effects from carbon monoxide poisoning: the vomiting, the headaches, the "ooh, I feel so bad."

cheers,
Michael

[TZ350]

But that means you miss out on the fun effects from carbon monoxide poisoning: the vomiting, the headaches, the "ooh, I feel so bad." cheers, Michael

Maybe we are not going to miss out on all the fun effects as the Govt is looking at legalizing the "Weed". Fun times to be had puffing on a roll your own while sitting in a cloud of volatile fumes expelled from carburetor blow back. Should be able to get a bit of the flash bang "ooh, I feel so bad." .... :laugh:

[AndreasL]

We are lucky for the input we get here from some very knowledgeable and respected 2 stroke experts...
So if you take the time to ask a question of the people who contribute their knowledge so freely on here on the thread.
Respect their time taken to answer it, by reading their answers properly.
Also consider it's not a interrogation, no ones obliged to answer.

Very well put and exactly my feeling.
My greatest fear, at least here ;), is if any of the above persons one day “doesn’t enjoy coming here and spend time and spread their know how” due to how they, or any one for that matter, are approached.

The “dinner party”-feeling and the possibility for n00bs trying the improve their 60 year old moped (that’s me) being able to get help and answers from world champions of the modern era...that’s totally unique. And it’s up to all of us to keep it that way.

[F5 Dave]

My dyno setup had a 4' industrial fan that you'd want to wear a jacket in front of in winter, but it struggled to keep the temperature constant.

[Frits Overmars]

343226
I think this pic is from the Garelli period?Yes it is. While Jan sat on the comfortable side of the double-glazed window, I was squatting next to the engine, wearing a welding helmet with clear glass, and earplugs and hearing protectors, and fiddled with the ignition. It was our first encounter with HCCI; it has taken us decades to understand what was going on back then.

[Pursang]

In the absence of a LIKE button.

What Husa and AndreasL said! :niceone:

Cheers, Daryl.

[husaberg]

Yes it is. While Jan sat on the comfortable side of the double-glazed window, I was squatting next to the engine, wearing a welding helmet with clear glass, and earplugs and hearing protectors, and fiddled with the ignition. It was our first encounter with HCCI; it has taken us decades to understand what was going on back then.

Jan does appear to have a mischievous grin on his face in that pic.

[andreas]

Either of these alterations are encouraged?

[Haufen]

First of all, I am sorry for the excitement I may have caused. It was not my intention to step on anyones toes. English is not my native language, so I may not always pick the correct word or come across in the right tone so that everybody can understand what I am after and in which way.

Secondly, I knew about the possibility of louvering the test cell fans, but was wrong about the range. I thought that one could adjust by a couple of mbars (+5 / -5 or so), but not that it would be possible to hold the test cell pressure stable throughout the whole year. In that case, the argumentation chain above is invalid.

Thirdly, I am all for respect between board members, and utterly independent of their 'rank'. This means also taking your time to read the questions (in this case Tim_Ey's questions) properly and adressing the items asked if one decides to answer.

And lastly, I am curious now:
By how much / in which range can you control the test cell pressure in this way on an average test cell?


It is pretty obvious from their success that Aprilia were knowledgeable and careful operators, so your point is exactly? .... :scratch:

My point is, that ambient conditions and the way power has been corrected is a standard information on any dyno sheet. And it is vital if you would like to compare and classify different measurements. At least now we know that the famous RSA dyno chart shows 54 uncorrected ps(?) measured at 1013mbar , 27°C.. This would be about 52,6hp corrected (25% humidity assumed) if measured at the same ambient conditions on wobblys dyno which seems to correct by EWG standards (k=1,000 @ 990mbar / 25°C / rh 0%)

[peewee]

But that means you miss out on the fun effects from carbon monoxide poisoning: the vomiting, the headaches, the "ooh, I feel so bad."

cheers,
Michael

gets more intetesting when theres some nitric acid vapor in the air :2thumbsup

[Frits Overmars]

English is not my native language, so I may not always pick the correct word or come across in the right tone so that everybody can understand what I am after and in which way.English is not my native language either. But I'd say your message came across. No hard feelings. My message is: you can ask anything, but you cannot demand it.


I knew about the possibility of louvering the test cell fans, but was wrong about the range. I thought that one could adjust by a couple of mbars (+5 / -5 or so)...It depends on the capacity of the blower, of course. You can visibly warp the ceiling of some test cells just by juggling with the louvres; you'll get scared to death when you calculate the force acting on the ceiling. And I know of a case where somebody attempted to open a test cell door while a test was in progress. The door broke his wrist...


I am all for respect between board members, and utterly independent of their 'rank'.I wouldn't dream of 'pulling rank'; I hate that kind of behaviour. But I do respect experience. I was lucky to work with the very best and I know nothing comes easy.


By how much / in which range can you control the test cell pressure in this way on an average test cell?I don't know what an 'average test cell' is capable of, but I'd say that 40 mbar ought to be achievable. Wob, what's your opinion ?


My point is, that ambient conditions and the way power has been corrected is a standard information on any dyno sheet. And it is vital if you would like to compare and classify different measurements.Of course it is vital information. In order to fully understand what you're looking at, you'd need not only know the ambient factors but also the engine coolant temperature and in fact all relevant engine data, like the set I posted as an example the other day, plus the mappings for rpm-throttle-ignition, rpm-throttle-powerjet and rpm-throttle-powervalve. All this information is accessible to the dyno operator, but it won't all fit on the graph. Besides, I was not trying to be comprehensive; I only wished to give an impression of things.

The standard values that you quote are new to me. I always went by standard conditions of 20°C (the Japanese use 15°C), 1013,25 mbar and 50% relative humidity.
As I wrote, SAE- and DIN-correction algorithms do not do justice to high-performance two-strokes.
I use the following correction algorithm, based on SAE 850085 (Eran Sher: A new practical model for the scavenging process) , SAE 930503, and my own findings.

corr.factor = (1013,25/Pdry)^(9/8)*((T+273)/(20+273))^(0,8) , where Pdry = actual pressure - partial H2O vapor pressure at actual temperature and relative humidity.

[katinas]

Either of these alterations are encouraged?

Andreas, I tested many times 1 alteration with different cut height, on similar Honda NS cylinders. This not changed max power, but rise torque at usual "dip zone" from 7000-8000 rpm.
Not tried 2 alteration, but this could be very good for piston ported engines. Hans Hummel always used interesting solutions on his cylinders for TZ.

[SwePatrick]

In below pic, the 'holes' above the wristpin is shortcircuiting my aux exhaustports with the transfers, i have no exchuse, i just measured wrong and now i have this piston, brand new with altered location of the ringstops.
And to spare me a lot of search of a new piston(67mm) i thought i´d ask an insane question here with the guys that has tested it all, you guys.. =)

Is there any way, easy way of filling these holes?
As is now it 'puffs' quite bad into the aux exhaustports when spinning the engine without the head monted.

JB-Weld, Pour in polyurethane, pour in molten aluminium, anything?

343232

Or just search whole world again for a suitable piston.....

[JanBros]

if I were to fill it with JB-weld or anything else , I would first put a couple of pins in the side of each hole that would prevent the whole part of coming out in one piece.

[SwePatrick]

if I were to fill it with JB-weld or anything else , I would first put a couple of pins in the side of each hole that would prevent the whole part of coming out in one piece.

Yes my former work was a concreteworker and i laid out a lot of, what is it called 'rebar' ,, so i got the same thought ;)

[wobbly]

The range of ambient air pressure we see in NZ is in the range of 990 to 1020 mBar , and we had no trouble at all of " correcting " this to an arbitrary
1010 as this was a very common average condition.
Yes Frits the pressure over area can be huge - sometimes it was all but impossible to open the door into the cell from the control room.
25*C was chosen again, arbitrarily , as it was nice to be warm in the cell in mid winter and it needed little adjustment during most of summer.
Bottom line was that the conditions were close to static for all testing - important for comparative purposes when ambient changes have greater effect than the element being changed.

[TZ350]

In below pic, the 'holes' above the wristpin is shortcircuiting my aux exhaustports with the transfers, Is there any way, easy way of filling these holes?

JB-Weld, Pour in polyurethane, pour in molten aluminium, anything?

343235



I have successfully glued the inside of the piston to block the bridge oiler holes.



230863

The oiler holes for the exhaust bridge need plugging.

230864

Normaly I would weld them but was persuaded to try gluing them with some super duper stuff that is as tough as shark shit.

230866

The finished result.

230865

[lodgernz]

I have successfully glued the inside of the piston to block the bridge oiler holes.

The stuff you mentioned: Is that it in the background, Belzona?

[peewee]

In below pic, the 'holes' above the wristpin is shortcircuiting my aux exhaustports with the transfers, i have no exchuse, i just measured wrong and now i have this piston, brand new with altered location of the ringstops.
And to spare me a lot of search of a new piston(67mm) i thought i´d ask an insane question here with the guys that has tested it all, you guys.. =)

Is there any way, easy way of filling these holes?
As is now it 'puffs' quite bad into the aux exhaustports when spinning the engine without the head monted.

JB-Weld, Pour in polyurethane, pour in molten aluminium, anything?

343232

Or just search whole world again for a suitable piston.....

maybe you can put pins from say a needle bearing. also maybe you can grind the side walls at the rear wider. even perhaps the roof at the rear taller. so basically the window gets larger as it goes toward the piston center. this would make it near impossible for epoxy to come out. also theres some over size piston for 250sx and such but I think are 68.5 mm.

[TZ350]

The stuff you mentioned: Is that it in the background, Belzona?

Yes .......


232140

After 40+ dyno pulls at near 30hp the glue blocking the oiler holes is still there inside the piston..

[SwePatrick]

I have successfully glued the inside of the piston to block the bridge oiler holes.

Yes, i had a slight memory you did =)
Thanks for the links to the post, i´ll read up again =)

[SwePatrick]

maybe you can put pins from say a needle bearing. also maybe you can grind the side walls at the rear wider. even perhaps the roof at the rear taller. so basically the window gets larger as it goes toward the piston center. this would make it near impossible for epoxy to come out. also theres some over size piston for 250sx and such but I think are 68.5 mm.

I understand completely, i had that thought also ;)

I can´t bore the cylinder any more, class rules :(

I was thinking something like this:
First, grind some grooves inside the pits,also grind the pit a bit larger then the opening and drill in some 'rebar' to secure it.
then shotblast the pits to get a rough clean surface.
Make a mold to get the pistonradious correct, drill small hole in the mold to pour the epoxi inside.
Heat up the piston some before as it tends to make the epoxi less viscous and grab on to the material better, say about 70-80 degrees.

Let it harden, and adjust after if necessery.

I had luck before with jb weld in other locations it seems to take quite good beating with heat, i have also tested added aluminium 'dust' from grinding aluminium into JB-weld, and by that got a very aluminiumlike material.
This engine is going away from methanol also as i want to test NOS instead ;)

[Frits Overmars]

EWG standards (k=1,000 @ 990mbar / 25°C / rh 0%)Haufen, I cannot figure this out: why on earth would one specify a standard relative humidity of zero percent? It would mean cooling all the incoming air in the test cell (and that is a lot!) down to 0°C in order to condense all H2O vapor, which would require a huge amount of energy, and consequently heating all that air up again to the specified ambient temperature, which would once more devour energy.
Jan Thiel and myself considered this approach in 1992 when we were working at Rumi, and it turned out that a separate transformer house would have to be installed for that to be possible. It would mean that 98% of all test facilities would not be able to meet the standard.

[husaberg]

Haufen, I cannot figure this out: why on earth would one specify a standard relative humidity of zero percent? It would mean cooling all the incoming air in the test cell (and that is a lot!) down to 0°C in order to condense all the


H2O vapor, which would require a huge amount of energy, and consequently heating all that air up again to the specified ambient temperature, which would once more devour energy.
Jan Thiel and myself considered this approach in 1992 when we were working at Rumi, and it turned out that a separate transformer house would have to be installed for that to be possible. It would mean that 98% of all test facilities would not be able to meet the standard.

I remember reading something Cameron wrote about the USA Kawasakis tuning operation was all done in the winter on the cold hell hole of a place.
They made huge HP in testing but for some reason not so much during summer and tended to have cooling issues.:rolleyes:

[jamathi]

Yes it is. While Jan sat on the comfortable side of the double-glazed window, I was squatting next to the engine, wearing a welding helmet with clear glass, and earplugs and hearing protectors, and fiddled with the ignition. It was our first encounter with HCCI; it has taken us decades to understand what was going on back then.

We were very amazed I remember!
We were trying to make an ignition advance curve.....
You could change the timing 10° or more and nothing changed!!!!
Later, at Aprilia we had a gear-change problem.
Does this ever happen with kart engines?

[SwePatrick]

Haufen, I cannot figure this out: why on earth would one specify a standard relative humidity of zero percent? It would mean cooling all the incoming air in the test cell (and that is a lot!) down to 0°C in order to condense all H2O vapor, which would require a huge amount of energy, and consequently heating all that air up again to the specified ambient temperature, which would once more devour energy.
Jan Thiel and myself considered this approach in 1992 when we were working at Rumi, and it turned out that a separate transformer house would have to be installed for that to be possible. It would mean that 98% of all test facilities would not be able to meet the standard.



You don´t copy the exact given enviroment in the dynocell just because the problems involved as you mention.
You just compensate against that 'standard day' that would be a perfect day, from your numbers on your mediocre day ;)

If dynoing 30hp on a bad day, the correction says what it might produce that 'perfect day', just to beeing able to compare to others.

[andreas]

Andreas, I tested many times 1 alteration with different cut height, on similar Honda NS cylinders. This not changed max power, but rise torque at usual "dip zone" from 7000-8000 rpm.
Not tried 2 alteration, but this could be very good for piston ported engines. Hans Hummel always used interesting solutions on his cylinders for TZ.

Yes I remember seeing H Hummels cylinders. I think in your pic 1, and probably 2 (as a double) is the second alt. Here is the same on an old cylinder where things went too far.

Warning: Photo is not for sensitive viewers.

[Haufen]

In below pic, the 'holes' above the wristpin is shortcircuiting my aux exhaustports with the transfers, i have no exchuse, i just measured wrong and now i have this piston, brand new with altered location of the ringstops.
And to spare me a lot of search of a new piston(67mm) i thought i´d ask an insane question here with the guys that has tested it all, you guys.. =)

Is there any way, easy way of filling these holes?

I have successfully done this in the past with a product called scotch weld by manufacturer 3m. You roughen up the piston (do undercuts if you can), clamp an aluminium stripe around it (pour it in soapy water before so that it does not stick as much to the epoxy - use spit if you forgot to prepare the soapy water), then put it in the oven to dry and harden (@120-150°C iirc). Before use, do re-work on the new outer shape of the piston if required.

I did several of these and all held up perfectly well for many hours at full load on the dyno on an engine with about 12k red line rpm.

Today, I would, however, roll a small aluminum sheet, cut out the required shape and have it laser welded to the piston.


Haufen, I cannot figure this out: why on earth would one specify a standard relative humidity of zero percent? It would mean cooling all the incoming air in the test cell (and that is a lot!) down to 0°C in order to condense all H2O vapor, which would require a huge amount of energy, and consequently heating all that air up again to the specified ambient temperature, which would once more devour energy.
Jan Thiel and myself considered this approach in 1992 when we were working at Rumi, and it turned out that a separate transformer house would have to be installed for that to be possible. It would mean that 98% of all test facilities would not be able to meet the standard.

Yes that's true. Fortunately, as pointed out be SwePatrick, you don't have to reproduce the exact target conditions, just get as close as you can. The measurement will then be 'valid' if the correction factor is between 0,96 and 1,06 (in EWG there may be other limits for other standards).

-----------

BTW, seems like wobbly is only around 2 hp away from the RSA with his KZ engine, despite all the limitations in the KZ rulebook. Pretty cool stuff!

(I got these number using the EWG standard to reverse - calculate the performance his KZ engine might have had when tested under the same ambient conditions as the RSA (and an assumed 25% humidity) the KZ would be at 51,9 and the RSA at 54 - both measured under the ambient conditions from wobbly's last dyno chart would leave the KZ at 50,5 and put the RSA at 52,6).

[peewee]

I can´t bore the cylinder any more, class rules :(
;)

it seems like millenium once told me they could apply plating to .36mm thick. this may let you go back to any common 66.4mm 250 piston. other wise devcon titanium putty may be the way to go

[katinas]

Detail pictures of KR 500 1979 crankcase

https://www.ebay.co.uk/itm/Kawasaki-KR500-1979-engine-cases-Classic-Racing-Motorcycle-Bike/352775303916?hash=item52230bf2ec:g:ZdEAAOSwMcZc3Z~ e

[SwePatrick]

I have successfully done this in the past with a product called scotch weld by manufacturer 3m. You roughen up the piston (do undercuts if you can), clamp an aluminium stripe around it (pour it in soapy water before so that it does not stick as much to the epoxy - use spit if you forgot to prepare the soapy water), then put it in the oven to dry and harden (@120-150°C iirc). Before use, do re-work on the new outer shape of the piston if required.

I did several of these and all held up perfectly well for many hours at full load on the dyno on an engine with about 12k red line rpm.

Today, I would, however, roll a small aluminum sheet, cut out the required shape and have it laser welded to the piston.


.

I ended up doing almost that, i´ve got a different epoxi from Loctite, cant remember the name as we speak, but it has been really good earlier when i have modified other things in aluminium.
However, i drilled a hole into the piston and locked a kevlarstrengthened m4 nylonscrew with the same epoxi(special ordered at my work long time ago, i work at ABB and are a 'toolmaker')
I heated up the piston to about 70 degree celsius after blasted and cleaned it, i did also undercut as you describe.
The heat makes the epoxi very low viscous so it grabs the blasted surface really good.
Then i use 'package tape' as a mold and filled half the pit, i don´t need to fill the whole pit.

It takes about 36 hours for this epoxi to fully cure.
I have noticed that those faster epoxies aren´t as good when it comes to 'adhesive', stick to aluminium, in other words.

343259

[SwePatrick]

it seems like millenium once told me they could apply plating to .36mm thick. this may let you go back to any common 66.4mm 250 piston. other wise devcon titanium putty may be the way to go

Good info, but i got a cast iron liner.

[TZ350]

Good info, but i got a cast iron liner.

You can plate an iron liner. Some have done it here to extend the life of the liner.

[SwePatrick]

You can plate an iron liner. Some have done here to extend the life of the liner.

if needing to revert back for 66.4 bore, i can always buy an new liner and port it the same as mine is now, it's cheaper as i can bore and hone the liner myself.

[andreas]

I ended up doing almost that, i´ve got a different epoxi from Loctite, cant remember the name as we speak, but it has been really good earlier when i have modified other things in aluminium.
However, i drilled a hole into the piston and locked a kevlarstrengthened m4 screw with the same epoxi(special ordered at my work long time ago, i work at ABB and are a 'toolmaker')
I heated up the piston to about 70 degree celsius after blasted and cleaned it, i did also undercut as you describe.
The heat makes the epoxi very low viscous so it grabs the blasted surface really good.
Then i use 'package tape' as a mold and filled half the pit, i don´t need to fill the whole pit.

It takes about 36 hours for this epoxi to fully cure.
I have noticed that those faster epoxies aren´t as good when it comes to 'adhesive', stick to aluminium, in other words.

343259

This epoxy you mention, is good for transfer ducts and what not? I've used Hagmans for this usually but if you find the loctite name I'd like to try it.