ESE's works engine tuner

[husaberg]

Als je niets aardigs te zeggen hebt, zeg dan helemaal niets

[wobbly]

TZ250 - 3XV Toroid with 10mm plug - 56 Bore
TZ400 - Toroid with 14mm plug - 66 Bore
Both 50% SAR.

[Haufen]

Looks like there may be some performance to be found in our good old two-strokes after all - even if the baseline is a certain "125cm³ motorbike racing engine from Aprilia" :drool:



Basis
A 125 cm³ motorbike racing engine from Aprilia is used as the basis for the simulations...


Abstract
The use of MAN-type loop scavenging port arrangements in a 125 cc two-stroke racing engi-ne is being investigated. These make it possible to provide larger cross-sections for the trans-fer ports, but at the expense of the exhaust port cross-section. The investigation is carried out using 1D calculations with GT-Suite. It is shown that significantly higher maximum outputs are possible in this way. However, this requires large exhaust widths, as otherwise the exhaust port is too small and the advantage of the larger transfer cross-section is overcompensated. Mixed forms between the original MAN loop scavenging and Schnürle loop scavenging can represent a good compromise. One open point is the quality of the scavenging. A study found in the literature on the use of MAN loop scavenging on a small engine shows significantly worse results than is known from large engines. There is still a need for further investigation here.


Conclusions
It has been shown that port arrangements of the MAN loop scavenging type have the potential to achieve higher peak outputs than is possible with conventional configurations. A configuration with the same maximum output as the basis but a wider power band is also shown...

You can access and download the paper here:
https://mobilityrxiv.sae.org/preprint/application-of-man-loop-scavenging-in-a-125-cc-two-stroke-racing-engine--sae-pp-00395

[yatasaki]

Haufen, I would say that we have loop scavenging if there is transfer port beneath exhaust port on existing cylinders we use today. ..short circuiting comes on my mind immediately .
Loop was abandoned on diesels because of scavenge efficiency, especially when long strokes were introduced.
Uniflow is unbeatable.

[porttiming124]

TZ250 - 3XV Toroid with 10mm plug - 56 Bore
TZ400 - Toroid with 14mm plug - 66 Bore
Both 50% SAR.

Woobly
Can you tell me if there is an ideal thickness of the aluminum between the bowl and the exterior?

[Frits Overmars]

Looks like there may be some performance to be found in our good old two-strokes after all.... You can access and download the paper here:
https://mobilityrxiv.sae.org/preprint/application-of-man-loop-scavenging-in-a-125-cc-two-stroke-racing-engine--sae-pp-00395This 'Novel Port Design' looks strangely familiar :msn-wink:
354753354752

[wobbly]

Porttiming 124 - the combustion bowl thickness depends entirely upon how much support the cover can provide.
You can regard the bowl inner face as a cantilevered beam , clamped at the bore and with a uniformly distributed load across it from the peak cylinder pressure.
In the 3XV design I ended up with 7mm thickness , as the cover , when the assembly was analyzed in FEA equalized the stress level across the bowl by its added support around the plug sealing face.
Without sufficient cover support the 6061 insert would come close to the the yield point of the material.

[porttiming124]

Porttiming 124 - the combustion bowl thickness depends entirely upon how much support the cover can provide.
You can regard the bowl inner face as a cantilevered beam , clamped at the bore and with a uniformly distributed load across it from the peak cylinder pressure.
In the 3XV design I ended up with 7mm thickness , as the cover , when the assembly was analyzed in FEA equalized the stress level across the bowl by its added support around the plug sealing face.
Without sufficient cover support the 6061 insert would come close the the yield point of the material.

Perfect thank you

[Flettner]

Haufen, I would say that we have loop scavenging if there is transfer port beneath exhaust port on existing cylinders we use today. ..short circuiting comes on my mind immediately .
Loop was abandoned on diesels because of scavenge efficiency, especially when long strokes were introduced.
Uniflow is unbeatable.

Uniflow has it's issues also...

[Haufen]

Haufen, I would say that we have loop scavenging if there is transfer port beneath exhaust port on existing cylinders we use today. ..short circuiting comes on my mind immediately .

I agree, short circuiting will be one of the 'hot' topics if there are transfer ports below the exhaust port. Speaking of hot - as will be temperature and heat transferred to the fresh charge in these ports. The former might not be that worse if the relative angle between the ports and the exhaust port is considered. For ports beneath the exhaust port, the charge would have to make a 180° U-turn to short circuit out of the exhaust. This is more than between the main transfer ports and the exhaust window in the conventional configuration - in most cases at least. The latter could be kept in check by water cooling and careful design of the coolant circuit, especially to shield the transfers from exhaust heat.



This 'Novel Port Design' looks strangely familiar :msn-wink:
354753354752


You mean the novel port design by Fleck et al from 2006 which is quoted in the paper in Figure 4? Other than that both designs have ports all around the bore, I don't see any resemblance? One is loop, yours is a symmetrical fountain (is there a correct wording for this?), one has one exhaust pipe, yours has two.

I would love to see the potential of such systems demonstrated on a running engine. From what I understood, getting your FOS system to work has been quite challenging so far - and there are also no results available (?) from the Fleck engine either. From a complexity and novelty (on smaller and high reving engines at least) standpoint, I would put the Fleck Design somewhere between the conventional loop and your FOS design.

[Tim Ey]

I got two questions for the Ignitec Freaks here:

1. Do you also get problems when using "Special" Settings for the bike? I think I killed 1-2 pistons with it &
I stopped using that now and returned to "Classic".

2. Ignitec claims that you need more than 14 Volts when revving over 12krpm. The control unit will be happy with 18 Volts. Battery can be build easily or even taken from a power tool (with balancer inside).
Are there any proper AC-DC regulators that are able to provide 18 Volts?
Or do I need to take a 12V & a 6V regulator and work with two batteries in serie? :facepalm:

[Mike Fisher]

I havn't run them yet but I've got 14.8V LiPo radio control batteries to try in a total loss Ignitech set up.

[F5 Dave]

I'd peak power at 13 and overrev from there. Running a convential cheapo rec reg and capacitor I could all gears it through the gears on the dyno reading a meter (or pc) and the Voltage would not drop.
CR250 alternator was enough to drive as well as an electric water pump. Are you over thinking things?

[wobbly]

Tim Ey , why would you need Special , unless running odd numbers of lobes to use a unusual rotor setup.
You need this when cutting one lobe in 1/2 for example to get proper twin fire on a RD/LC/RZ/Banshee
The Ignitech will be just fine on a 14.2 V normal charging system as long as you run the Ignitech coil , or even better the RGV/ RS Aprilia 125/250 coils.
Going to 15,000 with 14.2V charging from a CR250 stator was no issue on a KZ.
But for example the Ignitech will not function at all with a stock Honda RS125 coil as the primary resistance and inductance need to match the DC-DC Converter
and Honda did the matching in a different way.
I have run 15.6V Lith/Ion lightweight batteries to 14,000 on a twin with no issues.
I think you get a warning on screen over 16V and it will auto shut down above this level - 18V is impossible , or it used to be , maybe this has changed recently.

[flyonly]

Tim Ey , why would you need Special , unless running odd numbers of lobes to use a unusual rotor setup.
You need this when cutting one lobe in 1/2 for example to get proper twin fire on a RD/LC/RZ/Banshee
The Ignitech will be just fine on a 14.2 V normal charging system as long as you run the Ignitech coil , or even better the RGV/ RS Aprilia 125/250 coils.
For example the Ignitech will not function at all with a stock Honda RS125 coil as the primary resistance and inductance need to match the DC-DC Converter
and Honda did the matching in a different way.
I have run 15.6V Lith/Ion lightweight batteries with no issues.
I think you get a warning on screen over 16V and it will auto shut down above this level - 18V is impossible.

Woobly.

Is there a source for coils you could recommend. I am currently running total loss and the coil that came with the KTM


Sent from my iPhone using Tapatalk

[wobbly]

The RGV/RS Aprilia are available from bike wreakers , but are cheep as chips on Ebay.

[porttiming124]

Hello everyone.
I have an exhaust runner to fill in the bottom part along the entire length.
My runner is quite long (72mm) and it's difficult to access it with the tig torch.
I think I've already read Woobly or someone else recommending Hobart brazing rods as an alternative.
Can someone enlighten me on this please?

[Tim Ey]

Are you over thinking things?
Yes. Most probably.


The manual states that the ECU operates from 8-18V and shuts down above 20V.

I never got the issue that the engine did not want to rev further. Just wanted to see if anyone got other information. Thanks!


Wob: To be honest, I do not know how I got to special settings. I am using Ignitec stuff since more than 10 years. Looking back I apparently started using "special" three years ago. I do not know how I ended up there. Back to classic it is!

RGV/RS250 ignition coil is a must have.

[wobbly]

So no hand drawn Dyno files or CAD renditions - here is the real thing finally.
3XV going onto a 4DP , Ive got the hardware , now the hours of epoxy and porting starts.
Then onto the dyno to do the changes needed for the PV ,PJ and Ignition to suit the EngMod cylinders and pipes.

[wobbly]

You can use aluminum stick welding repair rods to fill in a duct - its easy as its so small and you can see what's happening.
But the trick is to angle the part such that the liquid flux material runs away from the new weld pool , this helps prevent porous holes in the filled in material.
Of course vapor blasting and or chemical etching away any old oil contaminants is mandatory.
Even then its not what you would call " pretty " but hey its supposed to make Hp not win a beauty contest.

[porttiming124]

You can use aluminum stick welding repair rods to fill in a duct - its easy as its so small and you can see what's happening.
But the trick is to angle the part such that the liquid flux material runs away from the new weld pool , this helps prevent porous holes in the filled in material.
Of course vapor blasting and or chemical etching away any old oil contaminants is mandatory.
Even then its not what you would call " pretty " but hey its supposed to make Hp not win a beauty contest.

I just had the nichasyl removed from them, they are very clean. Thanks Woobly for the recommendations.

[41juergen]

So no hand drawn Dyno files or CAD renditions - here is the real thing finally.
3XV going onto a 4DP , Ive got the hardware , now the hours of epoxy and porting starts.
Then onto the dyno to do the changes needed for the PV ,PJ and Ignition to suit the EngMod cylinders and pipes.

Looking forward to see the results!
BTW: I'm prepraring 3MA barrels with the same idea now, let's see how this will work out...

[wobbly]

41jueurgen - I did look at the 3MA but the boost port is miles too wide and way below BDC , also wasnt sure as its fitted backwards if the stud pattern is the same as 3YL/4DP and if the cylinder bore
is Desaxe offset.

[41juergen]

41jueurgen - I did look at the 3MA but the boost port is miles too wide and way below BDC , also wasnt sure as its fitted backwards if the stud pattern is the same as 3YL/4DP and if the cylinder bore
is Desaxe offset.
Of course you are right, but these cylinders will go on a 3MA engine.
Will see how far I can narrow the C port either with welding rods or welding itself. The plan is to shape the A port to a tear drop shape to get the aux ex port right..will show pics how far I can get..

[TZ350]

I think you get a warning on screen over 16V and it will auto shut down above this level - 18V is impossible , or it used to be , maybe this has changed recently.

Used to be 18Volts. I run a 5.0 Amp hour 18Volt Ryobi battery drill battery with my DC CDI 2 race Ignitec. I think they must have lifted the Voltage celling to 20Volts. Anyway it works Ok for me.

[F5 Dave]

Best check if CDI-2 and Race version if going that way.

[Condyn]

TZ, you are running it total loss I assume? How long does a battery last you? I am setting mine up tomorrow and have not been able to decide if I want a charging system.

[TZ350]

Best check if CDI-2 and Race version if going that way.

Yes, pay to check.


TZ, you are running it total loss I assume? How long does a battery last you? I am setting mine up tomorrow and have not been able to decide if I want a charging system.

Our preference is a 12V charging stator/rotor, 12V rectifier/regulator and capacitor (no battery) for a push and go system.

354768

Total loss, the 5 Amp hour battery lasts me the whole day.

Some times a charging system is not possible or practicable so we run total loss. As an experiment I connected the 18Volt 5 amp hour Ryobi battery to the car heater electric water pump that we use on our bikes. It pumped water for two hours before I got bored and went to lunch. With the 18V battery I had to use a 24V temperature gauge. The gauge switches the pump on/off and is very good at keeping the coolant temperature at its pre set target value of 45 deg C. 40 made the most power but 50 carburetted much better. So 45-48 it is. With these cheep Chinese switchable temperature gauges we found we can keep the coolant temperature in a very tight range.

[Condyn]

Thank you for the great info!

[wobbly]

TeeZee , when using a high voltage total loss supply, you used a 24V temp controller that is readily available - what effect does this have on the electric pump.
And secondarily what is that pump commonly used on , so I can get one.

[diesel pig]

TZ350, did you ever get that straight cut primary gear conversion done on your GP125?

[TZ350]

TZ350, did you ever get that straight cut primary gear conversion done on your GP125?

Yes, but no measurable power gain at the back wheel. Well not any I could measure with the dyno. Total disappointment.

[TZ350]

TeeZee , when using a high voltage total loss supply, you used a 24V temp controller that is readily available - what effect does this have on the electric pump.
And secondarily what is that pump commonly used on , so I can get one.

354771

The temperature gauge comes in three flavors 12V, 24V and 230V all with a 10A relay. We usually use the 12V version but with the 18V battery I found I needed the 24V one.

On 18V the 12V temperature gauge would work every time until the motor started then the gauge would switch itself off !!@#$$%????. Started again after I switched the motor off.

The relay switches out whatever the input voltage is. So 18V in on the red wire and you get 18V out on the yellow wire. Both black wires are common earth.

354770

Universal water pump. All from Aliexpress. Delivery is usually quite quick 2-3 weeks. Also you can setup on Aliexpress a Chinese version of Paypal.

The 12V water pump seems to handle the 18V Ok. Anyway I have used it running 18V at several race meetings now. Our other bikes use these pumps too but on 12V.

There are other axillary water pumps that push more water but of course, draw more current too.

[wobbly]

Cool , thankyou , you have a bench power supply, could you apply 15.6V to a 12V controller and see if it shuts down please.

[husaberg]

Yes, but no measurable power gain at the back wheel. Well not any I could measure with the dyno. Total disappointment.

I am guessing you could not float the main bearing?

[F5 Dave]

Yes, but no measurable power gain at the back wheel. Well not any I could measure with the dyno. Total disappointment.
I tried on RG50. No dyno difference back to back. :(

[F5 Dave]

354771

The temperature gauge comes in three flavors 12V, 24V and 230V all with a 10A relay. We usually use the 12V version but with the 18V battery I found I needed the 24V one.

On 18V the 12V temperature gauge would work every time until the motor started then the gauge would switch itself off !!@#$$%????. Started again after I switched the motor off.

The relay switches out whatever the input voltage is. So 18V in on the red wire and you get 18V out on the yellow wire. Both black wires are common earth.

354770

Universal water pump. All from Aliexpress. Delivery is usually quite quick 2-3 weeks. Also you can setup on Aliexpress a Chinese version of Paypal.

The 12V water pump seems to handle the 18V Ok. Anyway I have used it running 18V at several race meetings now. Our other bikes use these pumps too but on 12V.

There are other axillary water pumps that push more water but of course, draw more current too.

If you put a scope on the powerail you probably would witness the power rail being shaken up and down enough to cause issues and a reset but too fast to show on a meter.

[wobbly]

Just of interest if I upload the 3XV head cover model to Craftcloud 3D, the price delivered for two is around 380 USD. This cost the same amount here in NZD to be done in a CNC mill. I could reduce the material volume by about 25% as it was optimized / simplified for CNC , where it costs more to remove more.

[Gradella23]

Just of interest if I upload the 3XV head cover model to Craftcloud 3D, the price delivered for two is around 380 USD. This cost the same amount here in NZD to be done in a CNC mill. I could reduce the material volume by about 25% as it was optimized / simplified for CNC , where it costs more to remove more.

looks nasty wob, but isn't it always cheaper and better from a thickness/weight perspective to cast head covers since they're not too complex shapes?

[wobbly]

If I optimized the shape to be laser sintered ( minimized material volume ), I think that using 3D printed core/mold generation and casting - followed by subsequent CNC finish machining would be an interesting call.
The cost of CNC for a small part like this would probably be 50/50 CAM and setup Vs machine time, so maybe more cost effective if doing alot more than just 2 prototypes.
But as it stands it has minimal material removed as machine time is expensive in multi axis CNC.

[90GTVert]

Hope it's OK for a FNG to ask a question here.

I was told that I should rough up both the air filter and engine sides of a PWK carburetor for better performance on my 2T. I've searched, but haven't found much. Most just seem to polish the filter side. I've always thought that pre-fuel areas would be best polished. Once fuel is introduced, then some texture. Maybe this doesn't apply to carburetors? The person that told me claims to be the builder of some fast bikes, but it's the internet so I wanted to see what the real pros have to say about it and I never got any clarification from this person as to why they think I would want a rougher finish on the filter side.

[F5 Dave]

Get an old carb and make a real mess of it with a bastard file, take a picture and post it on same forum, say thanks, gained you 2hp.

Then carve some power grooves in an old head claim another 2.

If that hasn't aroused derision , try one of those propeller tailpipe fittings from the 80s, claim 7hp. And better gas mileage, obviously.

[wobbly]

Gotta have some golf ball dimples somewhere as well, then add some " turbo" slots in the crank flywheels.
But obviously adding boundary layer turbulence on the dry intake side dramatically increases airflow , once its been proven send the results to AirBus so they can rough up the intakes of their jet engines.
Come to think about it , Boeing are in trouble as well , maybe this is the silver bullet for intake efficiency and decreasing fuel consumption in commercial jet liners.
Sorry , not very helpful but I can think of plenty more suggestions - this is the Interweb as you said.

[_____]

Gotta have some golf ball dimples somewhere as well, then add some " turbo" slots in the crank flywheels.
But obviously adding boundary layer turbulence on the dry intake side dramatically increases airflow , once its been proven send the results to AirBus so they can rough up the intakes of their jet engines.
Come to think about it , Boeing are in trouble as well , maybe this is the silver bullet for intake efficiency and decreasing fuel consumption in commercial jet liners.

Made my day!


Sorry , not very helpful but I can think of plenty more suggestions - this is the Interweb as you said.
Slide50 additive, Nology wires & anything that is CNC milled and blue anodized?

BR Chris

[Pursang]

Save all that trouble, just buy a heavier power band.....the Red ones are usually the fastest!

[Frits Overmars]

I was starting to get seriously worried that no one here bothered to stress the importance of the powerband. Fortunately, Pursang saved the day.
354775

[90GTVert]

OK, got it. Thanks.

I've got an engine that refuses to stop killing pistons with even large amounts of fuel and some of the things the person said made a lot of sense so I was exploring the idea just in case I was missing something. It runs well, but by the end of 1/8 mile passes EGT is high and I have to basically drown it in fuel to finally cool it, but by then it's down on power. Piston shows detonation. Seems to be carb related, because it ran just fine with a 28mm VHST and now it's putting pistons on the wall of shame with a 34mm PWK. Simple answer is to go back to the VHST, but I've been trying to figure out why it's happening. Put a programmable ignition on it and put a 16* flat "curve" in it (what the manufacturer of the cylinder suggests at peak power) and it still did it, as it did with more traditional curves. I found that it was actually delivering less fuel with larger jets at one point, even though the bowl didn't appear to be draining (clear bowl & GoPro observation) so I used a larger bowl and made a main jet extender to put the jet near the bottom and then it was showing richer and richer on plug reads as it should, but still failed with high EGTs at the end of runs. It's to manufacturer spec on squish with no modifications to change compression or porting, aside from port matching at the base to the supplied gaskets. I have rode with 2 other people with the same engine (Malossi RC-One 94cc) with 34mm PWKs and neither had trouble with them. One is the exact same carb and I took his tune and it was 1400 EGT within 1/8 mile and even tried his entire carb and filter to make sure I didn't have a bad carb with no luck. I've ran a scope in the pipe (the pipe made for this engine) to make sure the stinger didn't have anything restricting it in case that was causing more heat. At this point it's quicker with the PWK, but even when I can match past best results for EGT observed at 60MPH during acceleration, it will heat up more than it should by the time I let off around 70MPH.

I just finished installing a detonation gauge (the one Wobbly has suggested to others in this thread). I've swapped atomizers, but some things I've read say they can cause fueling issues at sustained WOT if they aren't right. I'm going to dial timing back more at peak and probably go ruin more stuff once the new piston arrives.

Anyway, I wasn't trying to introduce stupid ideas and be a clown. I'm just grasping at straws because this has been going on for way too long now and every time I think I may have finally got it... it murders another piston. Thanks again for even bothering to read my posts.

[136kg136ps]

Okay, so seriously. Go to page 1 of this thread and also register at PitLane which is French forum and find the Aprilia threads.
Pay particular attention to Wob, Frits, Jan and Vannik but also to see all the mods which have worked or failed and WHY they faile or worked.


There is more two stroke wisdom in their posts than the entire rest of the internet combined. You can eliminate a lot of early trial and error by learning from the honest mistakes some the home mechanics here have made and how they remedied them using advice freely given.

[Frits Overmars]

Okay, so seriously. Go to page 1 of this thread and also register at PitLane which is French forum and find the Aprilia threads.
Pay particular attention to Wob, Frits, Jan and Vannik but also to see all the mods which have worked or failed and WHY they faile or worked.
There is more two stroke wisdom in their posts than the entire rest of the internet combined. You can eliminate a lot of early trial and error by learning from the honest mistakes some the home mechanics here have made and how they remedied them using advice freely given.The Pit-Lane forum in its entirety might be a rather large lump to swallow. And on top of that it's French. But no worries, if you go to
http://www.pit-lane.biz/t117p246-gp125-caracteristiques-aprilia-rsa
you'll find that the Frogs allowed me and other two-stroke characters to write in English. And as I keep pointing out, all photos are in English anyway.

As for KiwiBiker, this is the thread to visit, as 136kg136ps already remarked. I have fond memories of my first encounter with Wobbly, which you will find here:
http://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1130172752#post1130172752

I also posted some stuff in "FOS tips & concepts":
https://onedrive.live.com/?authkey=%21ABfdzwPhevl4qMs&id=8DD58EFB966FB3DC%216309&cid=8DD58EFB966FB3DC

[90GTVert]

Thanks for the links and advice. Believe it or not, I'm not a total noob to two-strokes. I'm a scooter guy that's been messing with them for roughly 20 years. Predominantly bolt-on and pretty mild porting and I do cut trenches in cases, which was how I was introduced to Wobbly's presence online. I've read Bell and Jennings long ago and got very little into Blair before realizing it was over my head, and I know of the legends like some of the present company. I have had this and Pit Lane bookmarked for quite some time now, but I run my own scooter forum and YouTube in addition to some locals that are looking for help and by the time I get done reading and replying to other people's problems I make excuses and don't want to spend more time reading daunting page counts worth of undoubtedly valuable info. I used to google search this thread and could find some answers easier that way, but that no longer seems to work.

Hopefully this gets posted soon, along with my previous reply. I've moderated and ran scooter forums for nearly 20 years now so it's really weird being the new guy awaiting approval.

[wobbly]

So you have confirmed that the bowl is not gradually lowering in level over the duration of your test time - yes.
The quick check would be simply to take off the bowl nut on both carbs , and using the fuel on/off valve on the tank , do a flow rate test on both carbs for a set length of time.
You might find that the smaller carb has bigger fuel passages and or a bigger float valve area when the floats are fully down.

If that isnt an issue then you need to do a needle tip/emulsion tube annulus area check at WOT.
This annulus should be at the very minimum about 30% larger than the main jet.
It can also be confirmed by taking out the main , or drilling out a huge sized one.
With no main installed it should carburate fine up to about 1/2 throttle, then go so rich that it dies up top - if not then the needle end is too big, and or is combined with a too small tube.
But PWK's dont have a replaceable tube from memory, so in that case it must be the needle.
I have seen this issue several times when people fit big PWK carbs on LC 250/350 and RZ racebikes , the needle tip annulus simply wont pass enough fuel at WOT.

The next area for investigation is the main air corrector jet or drilling.
If its too large the fuel curve goes progressively leaner with rpm.
The same can be said of the needle shroud height - the higher it is , the richer the carb will run , and thus obviously visa versa , with rising rpm.

Lastly , something you have also tested it seems is that if the ignition curve is overly retarded past peak power , trying to generate overev , then you can end up having to fit a huge main to cool the engine as the rpm goes past peak power.
This means you are using fuel as a coolant and to control the egt , not to make power.

Man 1400* is insanely lean on any fuel - so something is very , very wrong - just the mere fact it goes there sends alarm bells about lack of compression or ignition , as well as the obvious fuel restriction scenarios.

[Wos]

Maybe there is somewhere a leak in case, sealings, mainfold rubber that allows engine to breath fresh air!?

Especially check rubber, if its another one for the bigger carb ��

[90GTVert]

So you have confirmed that the bowl is not gradually lowering in level over the duration of your test time - yes.
The quick check would be simply to take off the bowl nut on both carbs , and using the fuel on/off valve on the tank , do a flow rate test on both carbs for a set length of time.
You might find that the smaller carb has bigger fuel passages and or a bigger float valve area when the floats are fully down.

I've observed it on a couple of different test days with a GoPro. Here's one before the main jet extender when it died and lost compression as I slowed from the 2nd pass (stuck ring), but the bowl wasn't really draining. This was with a 200MJ.
https://youtu.be/52bbQkNldqc?si=oZItL-sxVKKcaNVB


These are plug chops before the main jet extender, where you can see the mix ring disappearing as I went larger. Note : these are not test pass and immediate plug removal. I don't have a track or great spot to use regularly, so these all include a few miles to/from the spot at low throttle, but they seem to tell the story regardless.
https://i.postimg.cc/QC2DggCQ/P1000822.jpg

These were after the main jet extender. I think the 220 has less of a mix ring due to washing. The other guys with my setup are 175-195MJ so that's getting to be a lot of fuel. What's odd is that it ran the best time on one pass with the 220. For some reason the 210 acted very rich, with lower RPM and EGT.
L to R : Break-in ride (new ring), 205, 210, 215, 220, 210 redo.
https://i.postimg.cc/x8jMj5z2/IMG-4987.jpg

I should test the flow through the carb. I have tested supply flow and that was around 450ml/min using 3/16" hose from tank to carb. I found once that fuel supply flow was low some time ago and why surprised me. I had 1/4" hose up to the filter and then 3/16" to match the carb's barb and that mismatch caused flow to drop. I would have thought that the 3/16" would dictate max flow, but not that it would flow less than all 3/16". Did multiple tests and it was always better for me to use equal size hose on both sides of the filter. I haven't put the GoPro on to look at the carb with the bigger jets and main jet extender, but I saw the fueling and figured it was fine. Plus, by the time I realize I need to try something else, it dies again.




If that isnt an issue then you need to do a needle tip/emulsion tube annulus area check at WOT.
This annulus should be at the very minimum about 30% larger than the main jet.
It can also be confirmed by taking out the main , or drilling out a huge sized one.
With no main installed it should carburate fine up to about 1/2 throttle, then go so rich that it dies up top - if not then the needle end is too big, and or is combined with a too small tube.
But PWK's dont have a replaceable tube from memory, so in that case it must be the needle.
I have seen this issue several times when people fit big PWK carbs on LC 250/350 and RZ racebikes , the needle tip annulus simply wont pass enough fuel at WOT.


I haven't done any annulus test, and TBH I'll look up what that is. LOL
I have tried a needle first tuning method, where I ran it on the stand and made sure it broke up from richness with no main jet. That process is shown in the video below if anyone's interested.
https://youtu.be/UUzZfZHvsAU?si=1e5lTn0UYQv0shAP


The next area for investigation is the main air corrector jet or drilling.
If its too large the fuel curve goes progressively leaner with rpm.
The same can be said of the needle shroud height - the higher it is , the richer the carb will run , and thus obviously visa versa , with rising rpm.

I've never had to fiddle with either of these in all the years of tuning scoots, so if it comes to that I'll be looking up more info as well.


Lastly , something you have also tested it seems is that if the ignition curve is overly retarded past peak power , trying to generate overev , then you can end up having to fit a huge main to cool the engine as the rpm goes past peak power.
This means you are using fuel as a coolant and to control the egt , not to make power.

The last tests that I did were with 16* flat and a sort of clone of the curve that the engine maker's ignition provides with slightly less timing between low and high rev because I was pretty sure I heard detonation on my way back from test runs at about 12,000RPM and low throttle. Here's that curve. I did notice that it looks like less fuel on the plug with the more standard curve vs the 16* flat. Also, it wants to foul plugs with 16* at low RPM.
https://i.postimg.cc/KYvhYTHR/3.png


Man 1400* is insanely lean on any fuel - so something is very , very wrong - just the mere fact it goes there sends alarm bells about lack of compression or ignition , as well as the obvious fuel restriction scenarios.

Yeah, it was quite scary. I actually tested my EGT sensor and setup because I thought it had to be wrong if it didn't fail immediately, but I got away with it a few times and the EGT appears to be working roughly as it should as near as I can tell.


Thanks very much for the info/suggestions!!!

[90GTVert]

Maybe there is somewhere a leak in case, sealings, mainfold rubber that allows engine to breath fresh air!?

Especially check rubber, if its another one for the bigger carb ��

Good thought, but I leak test regularly. I had one that refused to stay in tune probably 10 years ago and found a crack in the case and that taught me to check whenever I make a change that affects sealing. Thanks.

EDIT : I posted a long reply to Wobbly with pics and video before this post, but I don't know where that went. Hope it's just still waiting for approval.

[F5 Dave]

I've used a main jet extender in desperation on long tracks before I realised that my carbs internal drilling feeding the float needle was actually the restriction.

But let's start at the beginning, or rather the end. What size was your stinger? As you raise in power it needs to increase. The perfect size to 20hp may kill a 25hp bike.

Oh and sorry for the ribbing at the start, but to be fair we did have a marvelous time.

[wobbly]

One more variable to throw in here - main jet sizing.
I have found it is absolutely necessary to use a set of pin gauges to size the main jets , the Dellorto ones are all over the place and are nowhere near what is marked on them.
Keihin QC may be OK, but I trust no one and would check anyway.
You can use an injector test rig as well to make flow comparisons.

[90GTVert]

I've used a main jet extender in desperation on long tracks before I realised that my carbs internal drilling feeding the float needle was actually the restriction.

I think the extender is a good thing. Not saying there's not other problem, but the jet seems way too high without it. It should be a little closer in the standard bowl, but the setup puts the carb at an angle and I like keeping more fuel in there.

Here's the standard setup with a larger clear bowl :
https://uploads.tapatalk-cdn.com/20240607/83832ec452afb3d2e1713fbc68fab0e8.jpg

My homemade extender :
https://uploads.tapatalk-cdn.com/20240607/aa7bee55f74ff942bf21007f357ba7d3.jpg

https://uploads.tapatalk-cdn.com/20240607/cc942a69168234a0b8dd1def23e141b5.jpg




But let's start at the beginning, or rather the end. What size was your stinger? As you raise in power it needs to increase. The perfect size to 20hp may kill a 25hp bike.
I will get back to you on that. It's the pipe made for the setup. It's a Malossi RC-One (MHR 94cc) with the Malossi MHR 94cc exhaust. Same pipe that the two other people I have rode with using the same setup and 34mm PWKs use. Pretty much everything on their bikes is the same setup, but it all works easily for them with no drama.


Oh and sorry for the ribbing at the start, but to be fair we did have a marvelous time.
LOL Glad you guys had a good time. No worries. I'm very appreciative for all the help. I can't tell you how frustrating it has been to be the guy that actually has a spreadsheet of 600 1/8 mile runs with EGT, RPM, temp and DA (every run with this engine for the last 2 years) and to try my best to be thoughtful and thorough and fail and fail while watching everyone else pop a 34mm on theirs, swap a few jets, use the popular needles (JJL/JJK) and live happily ever after. I thought for sure if I bought the exact carb that my friend uses on his, with his setup, I'd have little to do but fine tune and wheelie off into the sunset. WRONG. For most people that I talk to, this goes beyond any normal level of tuning and they are lost like me or I have some claimed pros giving me advice, but on YouTube comments and such you really have no idea who is suggesting things and most of the time another "pro" will contradict what they say.




One more variable to throw in here - main jet sizing.
I have found it is absolutely necessary to use a set of pin gauges to size the main jets , the Dellorto ones are all over the place and are nowhere near what is marked on them.
Keihin QC may be OK, but I trust no one and would check anyway.
You can use an injector test rig as well to make flow comparisons.

I didn't have anything for that size, but I did work a brass rod down as a sort of go/no-go gauge after the 210 jet was an outlier in the temp and RPM data collected. It was indeed somewhere between the 205 and 215, which makes it even more strange to me that it acted richer than the 215. It was about 200RPM lower on average during acceleration runs with 70-80F cooler EGT than the jets on either side of it. I don't have access to any flow equipment, but I did intend to take a close look and see if there's anything obvious like taper on an end or something different. I forgot about it after the engine failed again and I was just trying to source a piston.

[F5 Dave]

An extender is only any good if your float level is too low. It just buys you some more time, but the real problem is that the float level should not drop.

Running on a big angle, well, maybe. . But I'd want to get the carb a bit more level and get it working right then consider more angle if you free the demons.

So PWK is keihin. Oko and several others make clones. Their cloning machine is a bit variable. Some people get away with it , but I've spent a bit of time at the track helping the less fortunate ones. Usually with float and float jet issues I'd never really seen on my Japanese keihins.

[Pursang]

https://uploads.tapatalk-cdn.com/20240607/cc942a69168234a0b8dd1def23e141b5.jpg


Looks like a blob of water, in the well at the bottom of the jet pickup! That would move about under accell. & decell., and restrict the fuel flow through the jet!

[41juergen]

Thanks for the links and advice. Believe it or not, I'm not a total noob to two-strokes. I'm a scooter guy that's been messing with them for roughly 20 years. Predominantly bolt-on and pretty mild porting and I do cut trenches in cases, which was how I was introduced to Wobbly's presence online. I've read Bell and Jennings long ago and got very little into Blair before realizing it was over my head, and I know of the legends like some of the present company. I have had this and Pit Lane bookmarked for quite some time now, but I run my own scooter forum and YouTube in addition to some locals that are looking for help and by the time I get done reading and replying to other people's problems I make excuses and don't want to spend more time reading daunting page counts worth of undoubtedly valuable info. I used to google search this thread and could find some answers easier that way, but that no longer seems to work.

Hopefully this gets posted soon, along with my previous reply. I've moderated and ran scooter forums for nearly 20 years now so it's really weird being the new guy awaiting approval.

Have you ever been on a dyno with Lambda sensor measurement? Could give you a quick feedback whats going on with fueling over the rpm range...

[Betaversio]

Hello everyone!

Dear guru's, I would like to ask question.

We have been discussing with friends about pipe max diameter. It's quite clear that narrow pipe just produces weak pulses and when you increase diameter, effect of pipe increases. At some point, more diameter is not better any more, and question is, what is mechanism what defines that max diameter in particular engine with current scavenging?

There have been few ideas in thought. First, and most obivious, what have been around since these old books discussed above, is that too deep of a diffuser will take too much energy away from main exhaust pulse, and big positive return wave is too weak to be effective enough.

Second idea is that during scavenging, when exhaust pulse is about to start scavenging, too big of a pressure difference between exhaust port and part in cylinder near it without (at this point) proper flow from transfer port makes short circuit happening. Important thing in this case is that pressure difference comes from exhaust side and transfer flow is not yet fast enough to keep up scavenging loop working. If it was given more time, then there would not be any difference between making "vacuum" with exhaust or making "boost" with crankcase.

Third idea is about the same than last one, but more simpler way. It is just "too high flow velocity is too turbulent to make proper scavenging".

Second and third idea tells you, that in many cases bad scavenging needs weak pipe, becouse bad scavenging is so easy to mix up to be even worse. Of course, there is also cases when scavenging is so bad that anything you can flush through is just better. I have tried this one with one cylinder with horrible transfers. :bleh:

Any thoughts? Thank you

P.S. this have been wonderful topic to read

[koenich]

I can't tell you how frustrating it has been to be the guy that actually has a spreadsheet of 600 1/8 mile runs with EGT, RPM, temp and DA (every run with this engine for the last 2 years) and to try my best to be thoughtful and thorough and fail and fail while watching everyone else pop a 34mm on theirs, swap a few jets, use the popular needles (JJL/JJK) and live happily ever after. I thought for sure if I bought the exact carb that my friend uses on his, with his setup, I'd have little to do but fine tune and wheelie off into the sunset. WRONG. For most people that I talk to, this goes beyond any normal level of tuning and they are lost like me or I have some claimed pros giving me advice...

Just saw the Polini logo on the carb - are you sure it's not an underlying carb issue? I was at a similar point than you, although put in less effort.

Had my go with 3 different Polini PWK30 carbs and no matter which jets, needle or slide I couldn't get one of them to run even close to a good tune. After wasting a full day changing parts I questioned my own abilities or if the engine is the problem, so to rule out the engine being the problem switched back to the trusty OKO PWK30 and tada - bike ran like a champ again. Same story with a few friends Polini PWKs...

[Condyn]

I find the whole idea of “short circuiting with a big sucky pipe” to be misleading to some extent. Yes, there is a limit, but even on mediocre “developed” elevator shaft transfer geometry engines, I have had very very good results with increasing cone angles to what many would consider “ too steep “. Would I add a 4+ degree header that is 25 percent to this? No, but there is way more to the equation than just belly diameter.

[Frits Overmars]

Have you ever been on a dyno with Lambda sensor measurement? Could give you a quick feedback whats going on with fueling over the rpm range...
354784
..........

[wobbly]

I believe the first documented case of a belly diameter that was "too big " was documented by Erv Kanemoto , and he described its effect as " overscavenging".
He was working on an early TZ750 to be run at Daytona , and designed the largest pipes that could actually be fitted on the bike without issues of grounding them.
No matter what he did with these 110 diameter belly pipes , they always made less power.

This engine was very oversquare , had elevator shaft transfer ducts , and the A port front wall was not angled back well past bore center.
Thus the more efficient diffuser was, very early in the cycle , pulling mixture around the corner from the A port , as it had limited directional control or rearward bias.
As it turned out , this was confirmed later in the same series of cylinders with the TZ350 , and it wasnt until the 6 port G series , that 110 diameter pipes would be capable of
increased power output, and were fitted to the bike from the factory.

Regarding the use of available wave energy , this I believe is less of an issue , as a fatter pipe can be fitted with steeper rear cones , that does not act in the normal manner of severely restricting overev power.
A 24* included angle rear on a 110 pipe acts steep , on a 120 diameter belly it acts very shallow in its powerband effect, with more front side , less peak , and more overev.
Lastly , the idea of increasing scavenging via diffuser action efficiency has a very real and dramatic effect on power production.
But so the called " pumping " action of the case in being able to increase the Delivery Ratio is a very minor element in the overall engine efficiency , as increasing the case volume obviously
reduces this effect , but this is more than offset by that cases extra volume being available for an increased diffuser effect to act upon , thus increasing Scavenging Efficiency as well as the Delivery Ratio..

Moving along in development history we now have very narrow range of efficient case volume ratio's that work with the much better scavenging regimes as seen in later model designs.
For a reed low to mid 1.3 ratio , and for a rotary valve low to mid 1.2 ratio, and yes , the crappyer the duct geometry is , the smaller case , then works with a less efficient diffuser and that pairing
shows more power potential overall.
As always no free lunch , due to the action of transfer duct geometry being the final arbiter of what combination of case volume /pipe volume is the most synergistic.

[Condyn]

Wob, Great information, especially interesting is your explanation regarding the use of available wave energy, which has opened my eyes up even more to the fact that cone angles only paint part of the picture.

I also read the same Kevin Cameron article regarding the fat pipes, and Erv Kanemotos findings. This was early on in my pipe building journey, and because I had a crappy 70s Yamaha 4 port turd, I thought 110mm could be the limit. Slowly I started breaking this trend by pumping up the pipes. The A port has in fact been massaged for more rearward bias, and I do see the importance.
We are currently at 130mm in the belly section with more power across the entire curve.

With modern developed transfer geometry, or at least semi modern developed, Do you see any racing application where a smaller case than 1.2-1.3 could benefit on the track?

[Betaversio]

This belly diameter question came into think when pipes designed using EngMod did not work expectedly. Simulation calibration was done accordingly, and good pipe found in simulator was always "the fatter the better". Some of these pipes were built (in many engines, some bad and some good) and results were similar. Fat pipes did not rev as these supposed to be - and did not make power.

Then we started to think about this, and came into conclusion that becouse simu and scavenging model is 1D, it cannot tell when pipe is about to be too fat. You can of course change scavenging parameters, but it does not help when you don't know how much and in wich point to change them. So, we did not realize that and made too fat pipes.

At some point I was using kind of a "free search script" on EngMod to look after good pipe and it gave as result 140mm fat 660mm long (short..) pipe for 80cc engine that should rev around 12.5-13k peak power due to lack of time-area. In EngMod it gave great power. This did help when figuring out scavenging model problem as that pipe was so silly that only M.F. would believe in it :laugh:

[wobbly]

The 1.3 for reeds seems to be a hard fact. I tested a TM KZ10B model by machining 5mm off the reed block mounting face on the case.
So this gave alot smaller volume up around 1.32 - result , it lost about 1.5 Hp almost everywhere , and I tried softer and heavier reed backups and rejetted to achieve the same egt.
Net result - NFG , and no the reeds were not masking the boost port entry.
So next I added a 10mm spacer , this gave from memory about 1.285 CCR - again a power loss of closer to 2 Hp , but by using softer petals I got most of the front side back.
But by going a tiny bit softer by grinding small 1/2 moon cutouts just in front of the reed clamp plate , it absolutely shat it pants and all the peak and overev disappeared.

In the rotary valve engine I have tested ( in EngMod) a 110cc bucket race engine that TeeZee was working on , and he had machined off the flywheel OD and fitted a long rod.
This gave a 1.2 ratio , and my first reaction was , thats way too big as the Aprilia had around 1.24.
Well dream on - it lost a heap of power everywhere in the sim when I made it that smaller figure.
In the real engine , it would also have benefitted from less parasitic flywheel drag as well , a win /win.

Re the pipe wave energy usage. When I did the TM R1 pipe design the sim really liked a super steep last diffuser cone on a 134 Dia entry into the mid section.
This pumped up the front side dramatically , especially when I went under the 66% diffuser length guideline - longer made less power everywhere.
But going above 30* included on the rear cone did not seem to work as expected , so I reduced the mid exit to 132 and put in a huge series of 3 cones , with progressively increasing angles, as per the Aprilia layout.
This ended up with 28/31/33* angles and made more power everywhere , but I was skeptical and built and tested 3 different rear cone variations , including the 30* single angle.
Well , bow down to Uncle Neels , the sim was absolutely on the money.

[Condyn]

In the Sim, with your level of understanding and experience, I would be interested in what you observe at 600-800 below peak when shrinking the CCR to around 1.4 vs 1.3 on a reed motor.

[wobbly]

Man , the easiest question this week. 20 secs later here is the answer.
Wouldn't go there if I was you.
I could get some front side back with thin petals , but then they would go spastic up top , been there done that - no free lunch today.

[Condyn]

Thank you for taking the time.

[wobbly]

Pleased to help.

[90GTVert]

I've been spending a bunch of time testing and looking over things suggested to me related to tuning issues after swapping to a 34mm PWK.

Pretty sure I found why the 210 main jet acts totally different (richer) than the jets near it. These are Keihin jets, all ordered at the same time. The 210 has a large opening in the end. The orifice through was checked in the past and seems to be on par somewhere between 205 and 215. It's just the entrance that's bigger than every other jet I bought, Keihin or Stage6. Number stamp is on the side vs top like the others. Stamping size doesn't match on any of them.

https://i.postimg.cc/hGbYFSY0/P1010238.jpg


I made up a little test rig for checking fuel flow through the carb. Drilled a 1/2" hole in the bottom of a bowl and did multiple tests. I checked the 28mm VHST that I used prior to the 34mm PWK and a 28mm PHBH just as another reference point.

Fuel through PWK : 410ml/min, ~2.8mm float needle seat hole
Fuel through VHST : 520ml/min, 3.1-3.2mm float needle seat hole
Fuel through PHBH : 420ml/min, ~1.9mm float needle seat hole

Fuel through 3/16" hoses and filter without a carburetor : 870ml/min


Someone that saw my posts here was kind enough to email me a French language vid showing PWK mods for better fueling (linked below). I drilled out the cap covering it and then drilled the fuel passage headed to the needle area to 4mm. The holes around the float were enlarged to 2.5mm and the vent holes were done with a 3/32" bit. The fuel passage was sealed back off to the outside by tapping to M5x0.8 and installing a set screw with a very small amount of JB Weld on the threads to be sure it seals. The float needle chamber was deburred from drilling and polished with a Q-tip and aluminum polish.

https://youtu.be/EFXFvepG59c?si=VlGWV0ExmHVGAEVd

https://i.postimg.cc/6qjsk9yP/IMG-5102.jpg


I also removed the float stop in the bowl. It lets the float open just a tiny bit more.

https://i.postimg.cc/Z59ZhyPx/IMG-5104.jpg

https://i.postimg.cc/vHcC1w1Q/IMG-5105.jpg

I rechecked fuel flow and it went up to 560ml/min. That's almost a 37% increase!


F5 Dave asked about stinger size, so I checked the MHR 94cc pipe made for the RC-One and the Stage6 R/T 100 exhaust that I have. The MHR stinger is around 19mm. The S6 pipe is 22mm, but using a 20mm removable reducer. I have used the R/T 100 exhaust on this engine and it will allow more RPM, but 1/8 mile times are slower so I never actually use it.

https://i.postimg.cc/Qd7Pbgkw/IMG-5107.jpg]



Here are 20, 30 and 40 hole Polini atomizers. It's odd to me that the 20 and 40 have small holes and the 30 has large holes.

https://i.postimg.cc/PrJnm87n/IMG-5096.jpg


I searched for info about atomizers, but it was contradictory in some cases and left me uncertain overall. I thought about it and assume that holes open to fuel will richen the mixture some and holes open to air will lean it out a little. If that's the case, I wondered how many holes were bathed in fuel.

I marked the carb where holes should be, height-wise. All of the atomizers match up, having 5 holes per column, just different amounts of rows.

https://i.postimg.cc/pTW6RwbM/P1010294.jpg


After more testing, I think 1 atomizer hole is in fuel. That's with the carb straight up. I would think if fuel drains at all, then the fuel bathed hole becomes another air entry and leans out to some degree. If that's the case, I still don't know if I want 20 small holes or 30 large ones. I didn't notice any obvious difference when I broke the original 30 hole and swapped in a 20. Some like to say no holes on a 2T atomizer, but I don't have a 0 hole atomizer and I don't know that trying to fill with solder would be wise.

The atomizers are different IDs. About 2.71mm for the 20 and 40 hole and 2.76mm for the 30 hole. I don't have a really precise way to measure those, but somewhere in the ballpark and the 30 hole is definitely larger inside.


That brings me to the needle tip and emulsion tube annulus that Wobbly mentioned. I've used JJK and HLJ needles.

20/40 Hole Atomizer with JJL leaves me at about 28% larger by the time I get up to a 220MJ. With the HLJ I'd have to stay around a 210MJ.
30 Hole Atomizer with JJL allows just above 220MJ to stay 30% larger annulus. With the HLJ, about a 215 would fall in the range.

Here's where it is confusing and odd to me. Maybe this is normal, but I had to look up annulus so clearly I've never done this sort of analysis before. The nozzle/needle bushing/needle jet ID is 2.6-2.65mm. They make both of those sizes and I can't tell which, but I believe it's in that range. If the needle is going through there still at WOT, shouldn't that be a restriction? I need to check where the needle is for sure. If it's not in the nozzle, then I suppose the area is just fine and not a restriction so it's a false alarm. If it is in there, then at 2.6mm I'd need to stay 200-205MJ to keep that 30% margin. EDIT : The needle is out of that orifice and only behind the shrouded section at full throttle.


Regarding the pic that looked like a water droplet in the bottom of the bowl; that's just a water spot on the outside.

I've never had it on a dyno. I have had others suggest a wideband, which I have, but I haven't wanted to put a big bung in the exhaust so I haven't done it here at home.

To koenich; this is a Polini PWK. The only other PWK I have tried is my friend's identical PWK. Both of us got them from the same source and everything and they seemed to check out side by side. I actually chose it because he had it and the same engine so I thought it would be a matter of using the tune he came up with as the baseline and a little fine tuning and I'd be ready to roll. Did not expect to be 8 months in (carpal tunnel surgery in that time and waiting on pistons multiple times now) and still tearing up parts.


Thanks again to all that have read and replied.

[Tim Ey]

Regarding the aftermarket PWKs:
I fiddled a lot with the aftermarket stuff.

Stage6 anno 2006 gave my bike seizures.
OKO was fine.
Polini on an Aprilia RS125 did funny stuff in fast lefthand corners - it leaned out badly.

Apart from overflooding due do even the most microscopic debris, I never had an issue with original Keihin carbs.

Today, I would check every hole in the aftermarket carbs before mounting them. You'll never know what hits you.

[wobbly]

First off the main jet issue.
Having totally different entry geometry means that the actual flow rates will bear no relationship to each other.
You will have to make a simple flow rig using a bottle with a hose connected to the jet, and flow a set amount of liquid over a time base to find out what is going on. But having differing venturi setups is a huge spanner in the works.
I have never seen that in any other carb main jets, ever.

Re the emulsion tubes.
Again that is super wierd as I have seen dozens of Keihin 2T - 34/35/38 PWK carbs and none of them even have an emulsion tube.
The transition/ mid jetting is changed by the needle parallel diameter , then the taper.
This is a Keihin design " thing ". As all other carbs have screw in tubes of incremental size variation.
All the other 2T carbs with a variable diameter emulsion tube have no side holes, and the shroud height changes the fuel curve flow rate with rpm/ air flow

The only two stroke carbs I know of that have holes in the emulsion tubes are only a couple of years of Mikuni - RD Yamaha I think.
That system of emulsion tube air correction is for 4 strokes - but having said that I have no previous experience with carbs designed for " scooters ".
But anyway , those holes admit air from a main air corrector jet/drilling that comes in thru the front of the floor of the bellmouth.
The tube is in a " well " with fuel entering at the bottom and air at the top, and the holes change the fuel curve, more/bigger holes = increasing leaness with rpm/air flow.

Then you say the tubes are differing inside diameter and have differing hole configurations.
So in my opinion what you have is a bunch of jet parts that make it impossible to apply any logic whatever to get the carb tuned , as everything has more than one variable changing at a time.
An absolute complete nightmare when not all the parts being changed are from the same " series " of jet type, they should be all exactly the same apart from one variable.

[90GTVert]

Thanks once again guys. It's at least sort of nice to hear than I'm not totally crazy and inept. It drives me nuts that everyone else just throws these things on and goes. One guy uses coolant temp as his only indicator for the engine, which I explained is a terrible idea, and I'm recording RPM, EGT, ET, in a spreadsheet with practically a book now of each change made and it's just eating pistons that now I can't even find. I bought the last AA piston that the manufacturer has and they tried to offer me a BB or D as the others they had around. Awesome. That's why I went ahead and added the detonation gauge to it. I can use whatever info I can get. It sounds like I should just put a 28mm VHST that worked before back, but it kills me not to figure it out and I learn best through experience so I'm going through the wringer for no good reason probably... but at least the experience and you guys and others have taught me a few things. I think that's why all of us do this crap. We wanna be fast, but you gotta like to learn and experiment too.

[F5 Dave]

I'd try running the bigger stinger pipe and see if that brings your temp down as an experiment.

[koenich]

Agreed with Dave. 19 mm stinger (plus added dp of the 180° pipe to the silencer) sounds quite critical for an engine that should easily produce 40 HP on the crank...

[Frits Overmars]

Agreed with Dave. 19 mm stinger (plus added dp of the 180° pipe to the silencer) sounds quite critical for an engine that should easily produce 40 HP on the crank...It is. 40 crankshaft-HP requires a restrictor diameter (D5 in the drawing below) of at least 19,6 mm Ø.
And that's just the restrictor; the stinger diameter D6 must be clearly larger than that.
354794

[90GTVert]

Agreed with Dave. 19 mm stinger (plus added dp of the 180° pipe to the silencer) sounds quite critical for an engine that should easily produce 40 HP on the crank...

The manufacturer claims 31HP @ 13,800RPM and 14LB-FT @ 13,500RPM. I have seen one person on YouTube dyno one at 33HP, but his dyno also said it was at 10,500RPM. This thing is just waking up at that point so I don't know if something is up with his calibration or what. The same guy did his own scoot with the same Malossi engine and it was 29.75HP again at the odd 10,500RPM. Most say 25-30HP on a dyno from what I've seen.

52mm bore on 44mm stroke (93.4cc), 90mm conrod. 130* transfer, 195.5* exhaust durations. 14.6:1 UCCR. The engine kit comes with a 28mm VHST, but I swapped to a 34mm PWK as some say you can get a little more out of it that way. I have seen some improvement, but not much... of course I don't think it has ever been right either. For anyone unfamiliar, it's a whole kit. You buy an engine, but it's unassembled and the cases don't come anywhere near matching the cylinder base (cases are smaller). Some don't seem to touch it and some (including me) port match it. I'm sure that accounts for some variation.

Mine's not making 40HP. I've had it up to 85MPH. I don't really care about top speed though and I'm sure it could go a little faster. My best 0-60s and 1/8 miles are 6.9 and 9.6X @ 67-68MPH. I'm also not a jockey at 6'2 and 300lb (scoot and I are about 550lb) and the scoot is tall so I can't get into the throttle all the way quickly off the line. My smaller friend with the same setup and the same Polini PWK in a long low scoot does IIRC 5.7 0-60 and 9.1 @ 70-71 in the 1/8 and he can go over 90MPH. I'm not built for scooter racing, but I love the experimenting and trying to get quicker/faster... even if it isn't that fast. It's a street scoot that I actually ride. I've hit a deer on it that busted me up but the scoot came back to life, I've been hit by a hay bale lost from a truck ahead of me and wrecked it and it's still going. Used to ride 50-100 miles almost every night (not with this engine, but 90-110cc Minarelli clone strokers).

https://i.postimg.cc/76YBXD2T/351214831-229468493175039-164380313142533104-n.jpg



I got the piston and put it mostly back together. Just put the Malossi exhaust on last night. I think I'm going to start with it, because I already have multiple other variables from it's last runs and the exhaust changes the CVT tune, the RPM that it works at, and slows it down, and I think that's a lot for the first try. I typically do sets of 4 dragy passes when I test each change, back and forth, that way data stays pretty reliable when averaged. I may start doing 2 runs each time just to lessen risk slightly as I try to figure it out. If EGT still isn't looking good I will swap the pipe out. I'll be backing timing down slightly at power and more at lower RPM. Just trying to avoid detonation that is seen on the piston, but fingers are crossed that the knock sensor will help me see where it happens if it still does.

https://i.postimg.cc/QttvMDpr/Conservative-Compare.png

[Wos]

Bore 52... stroke 44...and engine is realy doing its max at 13500?...i am afraid it isnt..

[wobbly]

Usual story of an oversquare engine.

[wobbly]

I was going to edit the above and say " severely oversquare " that is always going to be limited in STA at high rpm.
But anyway the 3XV TZ250 mufflers are done , I am looking for a supplier here in NZ that used to have a huge bag of Silent Sport muffler packing and would sell any amount.
Anyone know who that was ?

[F5 Dave]

Silent Sport was the loose pack strand stuff. Local shop used to sell big bags. Went back to using Daytona matting as it was measurably quieter on the racebije.

[Flettner]

Wobbly, what pipe restrictor dia would you imagine a 65cc (say a KX65) would have?

Edit, I see Frits has a calculation, D5, but I need to know the HP first. Off to the dyno I guess.

[wobbly]

I have not done a 65cc engine in the sim. But a 50cc Athena race engine making 20Hp crank had a 16mm nozzle, and a KTM 85 race ( ie not MX ) with 38Hp crank had a 20mm nozzle.
Both optimized as 0.8 Mach in the nozzle.

[Flettner]

Im running 2x 17 dia at the moment, peaks at 11,300.
So far detonation is not an issue.
Unfortunately its a heavily under square engine at 48 × 58.
Will be rectifying that with a subsequent build, engine after next 54 × 55 , vairable disc valve, water cooled, twin blade powervalves (to suit the twin exhaust ports).

[F5 Dave]

Wobbly, what pipe restrictor dia would you imagine a 65cc (say a KX65) would have?

Edit, I see Frits has a calculation, D5, but I need to know the HP first. Off to the dyno I guess.

Oh lordy, are we talking about your twin pipe AG? The area of two xx mm holes vs the area of a single hole is what might be worth looking at?

[wobbly]

I think you would easily get away with 2X15mm in that.

[Flettner]

The pipes on the AG are a bit 'Dad and Dave' , the second bend on each pipe were hydroformed and not very well at that
Not accurate at all, so the next set of pipes have all been formed in press tools (many press tools). Ill make the restrictor part of the pipe interchangeable so I can experiment with different sizes.
After the restrictor (welded in 17mm section at the moment) the tail pipe opens out to 20mm out through the mufflers.

[diesel pig]

Leaving aside Throttle position sensor and solenoid controlled power jet issues* Would a 28mm Diameter or 36mm Diameter Carburetor be better from a Max Power vs Power band width point of view(far more important in circuit racing than people think). The 2 stroke in question would be hopefully a well tuned F4 Bucket 100cc.

* I think there are things that can be done for both things on Carbs that do not have them. Mind you if I am right about those things it brings into the Question those OKO copies of PWK 28mm over bored to 30mm,32mm and 34mm but are OKO's any good?

[wobbly]

Its not just a question of what carb and what size , its far, far more nuanced than that.
Take for example the very best of the 50cc FreeTech class engines - where essentially " anything goes ".
Many use a 30mm HV Lectron , this would appear to be extreme excess at a first glance, as when using a 30mm Dellorto carb a KZ 125 engine is capable of around 50 Hp at 13800 rpm.
But the HV Lectron has a 26mm venturi behind the slide , thus at part throttle it appears to the engines inflow as a much smaller diameter , but at WOT the carb is not in any
way the limiting factor.
At the outer extremities of what is possible, our old mate the Devil is very firmly in the detail.
And that my friends, is exactly what EngMod is capable of revealing to all and sundry.

[Frits Overmars]

Wobbly, what pipe restrictor dia would you imagine a 65cc (say a KX65) would have?
Edit, I see Frits has a calculation, D5, but I need to know the HP first. Off to the dyno I guess.Neil, note that the calculation of restrictor diameter D5 in the FOS pipe concept is based on crankshaft horsepower, not rear wheel power. So you'd need to multiply the power you measure on the dyno by about 1,15. Then the restrictor would match the power the engine is making now.
But the purpose of pipe improvement is to get more power so don't hesitate to be greedy and calculate D5 for a generous horsepower number.
Too large a D5 may hurt the power but it won't hurt the engine.

[wobbly]

Hey Mr Pig , regarding the carb question again , I am tending to the 36mm carb if the rest of the project is dialed into being used for roadracing.
The point here is that using the TPS and the Solenoid allows a longer pipe design , that will then overev easily by switching of some fuel just past peak.
If its as I suspect a WankStriker version , tap out the powerjet tube and machine out the wings in the bellmouth floor.
These work well in an MX scenario for throttle response below the pipe , but have a huge loss of airflow CFM when compared back to back with say a PWM.
You can tune the intake length slightly long to pump up the front side , and one of those sexy looking carbon fiber add on bellmouth extensions would help there as well.

[Grumph]

Any advantage to using a Smartcarb over a Lectron ?

Any comment on the Smartcarb generally Wob ?

[diesel pig]

Any advantage to using a Smartcarb over a Lectron ?

Any comment on the Smartcarb generally Wob ?

I will back that up, there general Smartcarb sexiness and easy way of tuning them(as I have seen in some youtube video's) that has got me very interested in them. But do you lose out on power at the very top of the rev's? or power band width? using them.

My first name is the same as Flettner's so by all means keep calling me Mr pig(i don't mind) it avoids confusion.

[wobbly]

I have fully tested the SmartCarb in two very different applications.
Technically the modus operandi of those and the Lectron are very similar, but the latest Lectron's now have alot more adjustability and their patented new needle is a real game changer.

The Lectron in HV series is better than the SC's egg shaped venturi in throttle response but the big unsolved issue with the SC is that it's all but impossible to get a pair to jet with equal EGT on a twin.
There is simply not enough adjustability in the " main " area of the needle , and there is an insufficient number of close tuned needle variations available - be it for a twin or not.

The Lectron has a simple powerjet , be it with a screw needle or jet swaps , so its dead easy to get a perfect WOT tune in tiny EGT increments.
I can easily keep an engine within 10*C of its perfect best power EGT on any day using the Lectron 's PJ - that tuning I found is impossible with a SC.

[Grumph]

Thanks Wob. Interesting re repeatability between carbs on a twin.

Maybe the "hand made" aspect counts against them here.

[wobbly]

Its not repeatability between carbs , its the crank windup in early TZ and case/manifold/pipe variations in later TZ that need split jetting and or split timing.
You simply cannot get small enough variation in the SC needle setting to equalize the EGT.
A couple of jet sizes in a PJ can fix it instantly.

[koenich]

Mind you if I am right about those things it brings into the Question those OKO copies of PWK 28mm over bored to 30mm,32mm and 34mm but are OKO's any good?
The OKO's are good in my experience, been using their PWK 30 since years on my 50cc (with Keihin jets and needle). However you can't bore them to much more than 30 mm, otherwise the slide won't have guidance and the wall thickness towards your manifold gets very thin. So if you are looking for sth > 30 mm dia, you need the bigger body...

[diesel pig]

You are right about it being a 36mm Air-striker Carb Wobbly, I was worried it was just too big to give me a good power band width. One of the other things that made me interested in Smart Carbs was there claim that it was not troubled by changes in Temperature and Altitude and watching you-tubes of guys on enduro bikes equipped with Smart Carbs riding from a cold damp bottom of a hill to a sunny clear top of the hill and saying there was no difference in the tune.
It's the one thing that annoys me about High performance Two Strokes is chasing EGT at a race meeting (I know it's important, That's why I am doing it) I just thought the Smart Carb would be cool to just set and forget it until the next change one did with the motor. Or am I just fooling myself?

[F5 Dave]

Intelijet?

Wob has commented before , what is consensus now for ease at a race meet?

[wobbly]

The SC and Lectron behave in the same way to changes in RAD.
That is way less sensitivity to those changes , I would estimate they are affected about 1/2 as much as the fuel blob producing normal type carbs.
The mechanism is based on the fuel being " sheared " into much finer droplet size by the action of the flat sided needle , and changes in air density change this effect.
Its got bugger all to do with the smoke and mirrors marketing waffle produced by SC about the Aux Venturi above the bellmouth thats connected to the top of the fuel bowl , as a
Lectron doesnt have that but it works in exactly the same manner.
So you would still need to change the fueling on a cold morning warmup , but then only have to change it once later in the day when its steaming hot and the Density Altitude
has increased a 1000 ft.
I would have had to do 4 jet changes in a normal carb to keep on the money.
And that right there is the downfall of the SC , making small accurate main jet changes is all but impossible - the Lectron PJ takes a minute and is repeatably accurate every time.
The Intelijet works well in that it adds air correction, that not only changes the fuel curve it increases atomization.

Edit - I have asked Lectron about adding an air corrector to the PJ circuit ( as SC flatly refused to do this ) and they said they had done testing on this very thing , but felt it added too much complexity
( another tuning variable ) for negligible gain in performance.

[F5 Dave]

Certainly the intelijet is cheaper if you already have pwk. Or even before.

[diesel pig]

I must say I was very impressed by the Smart-Carb Tuning on the you-tube videos they just stopped the motor. Held the throttle wide open and turned one knob on the top of the carb for tuning Right for Rich and Left for lean. I had a quick look at the Lectron site. I must admit I could not figure out how one did the tuning Rod the power jet was obvious but not the Rod to me. So Wobbly, I think you leaning towards the Lectron and one tuning change per day is way easier than four to me. So a Carb with a tuning Rod instead of needles and jets still has my interest. But what size and brand do you think one should be picked by someone who is a keen 100cc 2-Stroke bucketer but no expert tuner?

[wobbly]

So here is my take - you want a tuning rod and you want it simple to change the jetting.
The Lectron also is a very simple scenario for adjusting the rod , but as it has an adjustable PJ thats not even necessary.
They do have a screw needle adjuster setup for the top of the PJ , so a 10 sec screwdriver adjustment of that sounds like you.
They have a needle turn/jet size chart to follow , so thats simple as well.
As for size I think the ideal would be a 34HV as this has a 4mm smaller venturi behind the slide and at part throttle that gives you the response of a 30mm carb.
Perfect combination in a roadrace bucket scenario where you are never going to have a " real " close ratio cluster.

[crbbt]

Look how long it took lectron the add a proper TPS because of "complexity"

[wobbly]

So you tell me how many carbs have ever had TPS on the market , its confined to a super small 2T road race and MX number and the rest are 4T that usually have injection now anyway.
If I wanted a in situ TPS the only 2T carbs are the SPJ on RS125/250 Hondas , and a few of years of MX bikes in the early 2000 that had electronic servo's and or PJ.
Lectron with their new patented needle now have the opportunity to sell larger numbers of units into the older Superbike market and the 4T MX carbureted market.
So their TPS is just an extension of market sales capability , not " complexity " as such - a bit of an unfair criticism in my humble view.

[diesel pig]

One thing I notice when i was on the lectron site was the power jets on there carbs did not appear to be solenoid controlled. Or maybe this is not important to get overrev with tuning Rod Carbs?

and you are right on the gearbox Wobbly, Even taking a advantage of all the micofiche sites on the Web these days. The best I could do was mix and match gears from different models of the same basic engine to get a "closer" than stock gearbox but far from close ratio gearbox.

[jbiplane]

This is another test for my fuel injected 2-stroke boxer using as load air brake = small propeller with adjustable blade angle
2-stroke boxer resonator add just 17% of power, but bsfc become much better

https://www.youtube.com/watch?v=CWHl829Qqcc

[wobbly]

The solenoid PJ situation I am working on right now. It appears that all the suppliers of the original Mikuni setup are out of stock as the kit is NLA.
I need the solenoid setup for the 350 YPVS racebike I am doing that has just been fitted with Billetron 38HV with twin PJ in place.
These sit dead square on the reed block face using Mikuni ovel carb rubbers - easy free Hp.
The switched jet is a deadly setup for overev , be it just off/on/off or PWM with TPS, available on Zeel or Ignitech's
The Dellorto solenoid used on the RSA I believe was an air control of some sort for a Weber fitted to Fiats - so Im looking to adapt that sort of thing onto the standard Mikuni PJ kit.
Will post the result on here as soon as I have it sorted.

[190mech]

wobbly,
I seem to remember that Jan Thiel said they used off the shelf Keihin solenoid valves on the Dellorto for the RSA. He even gave the part number..

[diesel pig]

The solenoid PJ situation I am working on right now. It appears that all the suppliers of the original Mikuni setup are out of stock as the kit is NLA.
I need the solenoid setup for the 350 YPVS racebike I am doing that has just been fitted with Billetron 38HV with twin PJ in place.
These sit dead square on the reed block face using Mikuni ovel carb rubbers - easy free Hp.
The switched jet is a deadly setup for overev , be it just off/on/off or PWM with TPS, available on Zeel or Ignitech's
The Dellorto solenoid used on the RSA I believe was an air control of some sort for a Weber fitted to Fiats - so Im looking to adapt that sort of thing onto the standard Mikuni PJ kit.
Will post the result on here as soon as I have it sorted.

And that picture Wobbly posted confirms what I was thinking about how to get a solenoid to work on a carb with a power jet that did not have solenoid fitted at the Factory. kudos Wobbly

[husaberg]

wobbly,
I seem to remember that Jan Thiel said they used off the shelf Keihin solenoid valves on the Dellorto for the RSA. He even gave the part number..


And that picture Wobbly posted confirms what I was thinking about how to get a solenoid to work on a carb with a power jet that did not have solenoid fitted at the Factory. kudos Wobbly

My understanding was wn the Aprilia they originally used a stepper motor and it could progressively shut off the flow I assume using a needle valve
It was an idle control stepper motor off a Fiat uno. I think they later went to a Keihin part of an RS125R
DP get a Keihin off latish NSR250, they have a tps and are likely a better size. ALso factory downdraft.
you can get kits for them to give them more adjustability
https://nsr-world.com/tuning/250-tuning/carburation-index/carburettors/
Dave was trying to steer you to a dial a jet
https://thunderproducts.com/product-category/fuel-systems/dial-a-jet/
https://thunderproducts.com/product-category/fuel-systems/intelajet/

[diesel pig]

Thanks Husaberg and Wobbly for both your input. Much to think about. The thing I have to keep in mind is being just one guy at a club meeting is to keep the Carb tuning steps as simple and straight forward as possible to keep on top of the two strokes I am running.

[speedpro]

What about using a boost control PWM solenoid to bleed away the vacuum signal from the powerjet? You'd have a normal powerjet circuit but with a T-junction with the solenoid off to the side. When you don't want the powerjet to supply fuel energize the solenoid to allow air to be drawn in rather than fuel to be drawn in via the jet. If it was progressive via the PWM control you would have air mixing with the petrol from the jet before it got to the powerjet tube in the throat of the carb. The desired fuel would get there that little bit quicker due to the airflow which it would mix with plus instead of globs of fuel it would be a mix of fuel and air.

I had a much less sophisticated version on my turbo McIntosh but it resulted in the same outcome. A mixture or air and fuel entered the opening of the carb through the "jet"

[Frits Overmars]

My understanding was in the Aprilia they originally used a stepper motor and it could progressively shut off the flow I assume using a needle valve.
It was an idle control stepper motor off a Fiat uno. I think they later went to a Keihin part.Exactly
...

[ken seeber]

PISTON PIN PLUGS.

As it turns out, Vortex have been making plugs for their 60 cc MiniRok kart engine for some years. So, if you've got an engine with a 12 mm pin, here's your chance. Approx 15 Euro each from Mondo Karts. Looks like some form of PEEK high temp material and most likely from bar stock.

Begs the question as to whether they do (or could do) a version for their (or any) KZ engine with the usual 15 mm pin. Obviously the dimensional relationship of the circlip groove to the adjacent piston skirt face would have to be maintained.


354831

[jfn2]

I ordered a set of these awhile back but never did get them, so I made my own from torlon. I purchased a foot long rod and I have alot of material left-over. I designed them just like Frist's pictures and have had no problems. I used them on a KTM314 motor. Fantastic motor! It was used for GNCC racing here in the states.

[Peter1962]

I ordered a set of these awhile back but never did get them, so I made my own from torlon. I purchased a foot long rod and I have alot of material left-over. I designed them just like Frist's pictures and have had no problems. I used them on a KTM314 motor. Fantastic motor! It was used for GNCC racing here in the states.

314 ? Did you stroke the crankshaft ? Or is it a big bore ?

[jfn2]

Peter
Stroked 3.5mm with a clean-up bore. (72.16mm I think?) And it seems I was mistaken. The cc's only come out to 309cc's. I built a Yamaha engine to arround 314cc's or something like that.

[wobbly]

After alot of on line research here is what I believe is the simple/cheap version of a solenoid PJ , as the idiot price original is now NLA..
The tube solenoid just needs a threaded adapter to the much cheaper and still available Mikuni standard PJ kit , and a jet or insert fitted inside the holder that is much bigger than that used in say a Lectron powerjet system.

https://www.summitracing.com/search/part-type/powersports-carburetor-jet-kits/product-line/mikuni-power-jet-kits

https://nz.element14.com/ledex/195203-234/solenoid-tubular-push-continuous/dp/1331806

Here is a setup I have cobbled together from bits I had in my parts boxes - perfect for Mr Pig if he wants it.
This combined with the lever type TPS ( same as PWK style ) now available on the new Lectron carbs would be the trickest setup.

[diesel pig]

This combined with the lever type TPS ( same as PWK style ) now available on the new Lectron carbs would be the trickest setup.

It must be new I could not find it on there site. Must not of updated the site yet.

[wobbly]

Can we get .mov video added to allowable file posting on here ?

[husaberg]

Can we get .mov video added to allowable file posting on here ?
I have asked the site techy administrator.

[Frits Overmars]

Can we get .mov video added to allowable file posting on here ?

I have asked the site techy administrator.
Having .PDF allowed would be fine too. I'm testing it now. So if I succeed, you can forget about this post.
354834

[136kg136ps]

It worked for me Frits. Firefox and in the US.

[F5 Dave]

Android here, working well.

[Jonny snatchsniffer]

Hi all, 1st post on here but what a thread this is, taken a while to read but have a few pages left, brilliant

Re- polini carbs, out of the box they are proper shite and the reason being is that it doesn't have a normal 2 stroke needle shroud, this makes jetting nearly impossible with wot needing bigger jets an richer needles, I have one on my lambretta and had to get the lack of shroud pressed out and a normal one pressed out
I'd get a genuine pwk 33 or 35mm
I have a pwm 38mm on my 28hp vespa polini 130 road scoot and its easy to jet and needle

[wobbly]

I tested the Keihins back to back for the SKUSA Stock Honda classes , the PWM is easily the best.

[F5 Dave]

Strange, I've had little to do with PWM as PWK so ubiquitous esp in dirt circles where we feed a lot of parts from.

Attack of the Clones: I see Aliexpress etc offer PWM things too. Buyer beware in my opinion.

[wobbly]

Yea , I just check on Ebay , PWM 38 from China $90 NZD , from Germany $ 900 NZD.
You decide who is taking the piss.

[Jonny snatchsniffer]

I got that pwm for £26 of ebay brand new in box
Found out more about the polini pwk carbs
You cant adjust the float height as they ha a light float and a heavy one, use the heavy one if you have vibrations lol
There is also something called the air brake jet on the back of the carb at around 6 o'clock at the bottom of bellmouth, this should be closed for 2 strokes and open for the foul strokes, apparently this stops air entering the atomiser as there should be no holes in 2 stroke atomiser, the more holes in the atomiser with the open air brake jet the leaner it will run, this is for emissions crap
So for the 2 stroke you need to blank off or close the air brake jet, fucking mental, no wonder everyone has trouble with them as you may have been given an open one as to a m8s closed one
Still prefer the proper keihin, shame it goes from 28mm and then straight to 33 for the pwk, but don't waste money on the air striker as its just another gimmick and for me done nothing to performance.

Quick question, ive put a 54.5/105 crank in my vespa instead of standard 51/97 increasing the stroke, this means that with my particular barrel the piston ends up around 1.3 mm below exhaust and transfers at bdc, the scooter fraternity here say this isn't a problem but would it be beneficial to lower the bottom of the transfer ports to top of piston at bdc or not?

[Jonny snatchsniffer]

Strange, I've had little to do with PWM as PWK so ubiquitous esp in dirt circles where we feed a lot of parts from.

Attack of the Clones: I see Aliexpress etc offer PWM things too. Buyer beware in my opinion.
The pwm was make for road racing, but then they made short body pwk's for the mx bikes, pwm is for outright power

[wobbly]

I would say leave the bottom of the Exhaust port above BDC to help with short circuiting , but as the bulk of flow exiting the transfers is around BDC then having a big negative step there
will absolutely ruin the flow stream regime , but you still need the duct to be reducing somewhat linearly in area as it approaches the port , so how you drop the floor needs some thought.

And if you have done a port STA calculation , it will of course assume the port area goes from the timing height , down to BDC.

It has also been suggested having the transfer bottom flush will help the mixture adhere to and cool the dome.

[Vannik]

And if you have done a port STA calculation , it will of course assume the port area goes from the timing height , down to BDC.


Not the calculation in Dat2T, it uses the actual port shape and timings.

[husaberg]

Having .PDF allowed would be fine too. I'm testing it now. So if I succeed, you can forget about this post.
354834
I have had a few occasions when pdfs failed. I assume it was due to size. I will ask about that as well.
I had a feeling there used to be something like 2mb.
when this is the case you can save say first x pages as separate files by printing as a PDF using the the printing range to say 10 pages, so it will be 4 files instead of one big ones..



Valid file extensions: doc dxf gif jpeg jpg kmz mp3 pdf png pps ppt psd swf torrent xls zip

[F5 Dave]

The pwm was make for road racing, but then they made short body pwk's for the mx bikes, pwm is for outright power
I changed the long pwk for a short one on my GG 300 Enduro with an extender on the bellmouth. Best improvement was probably it being virtually new.

Bear in mind the Enduro an MX bikes have different needs from roadrace. As a long time 50cc racer I appreciated both.

Bigish 2 stroke dirtbikes are absolutely awesome. Different mindset in single-track forest.

[90GTVert]

Found out more about the polini pwk carbs
You cant adjust the float height as they ha a light float and a heavy one, use the heavy one if you have vibrations lol
There is also something called the air brake jet on the back of the carb at around 6 o'clock at the bottom of bellmouth, this should be closed for 2 strokes and open for the foul strokes, apparently this stops air entering the atomiser as there should be no holes in 2 stroke atomiser, the more holes in the atomiser with the open air brake jet the leaner it will run, this is for emissions crap
So for the 2 stroke you need to blank off or close the air brake jet, fucking mental, no wonder everyone has trouble with them as you may have been given an open one as to a m8s closed one
Still prefer the proper keihin, shame it goes from 28mm and then straight to 33 for the pwk, but don't waste money on the air striker as its just another gimmick and for me done nothing to performance.



Thanks for the info on the Polini PWKs.


In case this is useful for anyone, I bought a few more main jets for my PWK and spent some time testing jets that overlapped each other in size to see how it turned out. I got some real Keihin jets this time. Turns out the ones that I thought were Keihin (with the oddly ultra rich 210 jet that I showed) were Niche Cycle.

2L bottle with bottom cutout, upside down. Cap tapped for hose barb, epoxied in because the caps today are so thin that it won't seal otherwise. 3/16" hose > shutoff > 3/16" hose. Main jets fit well in the hose. 24" from end of hose to top of water level. Water level marked on bottle so I could make sure it stayed the same for all tests.

https://i.postimg.cc/FKnVG854/IMG-5162.jpg

This is what I came up with. I think the flow numbers are probably somewhat arbitrary. I've got 24" of water above the jet, not sure on volume. If you tested with more or less water you'd get different results. I just wanted to be able to compare what I have rather than worry about some standard. I almost got wrapped up in a project to build a rig that would keep a set height of water above the jet at all times and horizontal exit flow at the jet after reading about Ford Zenith main jet testing and then I thought... you're still waiting to order a cylinder kit (circlip came out and trashed the current one with a brand new piston)... why spend money testing these things and turn it into a whole thing? I assume flow would be greater with water level always constant instead of draining, possibly changing results with larger jets more than smaller... but I think this comparatively simple method still tells a story.

I don't have full sets of all jets, so that's why data points are missing. GZYF are the amazon jets. Flow numbers are ml/min. All tests were 20 seconds. 3 tests gives a 60 second flow figure. Better to do 2-3 tests to watch for inconsistency than to do 1 60 second test for each IMO... and I'm transferring out of a beaker and into a graduated cylinder for more accurate measurement... which takes a lot of time so doing 3x the volume multiple times would greatly increase time/effort. I assure you, it's not just pour in and look. I'm tapping and smacking stuff trying to get air bubbles out and it's a whole process.

https://i.postimg.cc/x15RNq6q/Main-Jet-Flow-Test.png

Niche Cycle jets are to be avoided! They are the leanest of all of the jets, but even worse than that is that they have a huge spike at 210 and otherwise there's only minimal change from 205 to 215.

The amazon jets aren't awful... but then 235 and 240 flowed less than the 230. Not by a lot, but it's dangerous to think you're adding fuel while reducing it any.

Both Keihin and Stage6 jets seem to go up at a good rate without anything that alarms me. Stage6 jets flow slightly more than their Keihin counterparts and their flow rate change doesn't look as steady. I think both are just fine choices though.

What I think I learned is what I've known for years... go with big name brand jets and buy as many as you can from one manufacturer. Also, orifice size is what we usually think about, but entry design/size matter quite a bit.

Example 1) The 210 in the Niche jets that flows way more than the jets around it. Orifice size falls in line, but the entry on the 210 is huge compared to the others.

Example 2) My drilled main jet, 2.5mm (250) flows less than the amazon 250 jet. The smaller GZYF jets flow as much as it does. The drilled jet is one diameter all the way through. The others have a larger area at entry.

[wobbly]

You are right off course Neels , but I was alluding to the fact that if a cylinder is lifted and is set to a specific timing, that timing will not
have the " correct " area and a port, with its floor above BDC, extra timing would be needed to generate the required STA
But yes EngMod can have that higher floor timing incorporated , and thus the STA created will be with the actual reduced area generated by the roof and floor heights from TDC.
But as we spend alot of time trying to center as big a depression at the Exhaust port as possible around BDC , it seems counter intuitive to me to firstly have to lift the transfers higher
than otherwise would be the case , and have to do this as the transfer floor is above the piston . What possible advantage could this approach accrue.

[Jonny snatchsniffer]

I originally went for the 54/105 crank as the bgm one twisted on the dyno, at the time my budget was was pretty much limited as the bgm so called race crank was only £160 and only needed the sealing pad removed from cases to fit, the polini crank was a 52.8 stroke with a 102mm rod to make the cc 135 to comply with the Italian polini cup race series, standard is 51/97 and at the time the polini was about £650, 3 times my budget.
Wish I'd gone with that in the first place as the bgm twisted so much, about 1.2mm runout it also made the flywheel magnets smash into the stator laminates, rendering it useless, it also ruined the cases with the drive side bearing spin in the case wearing the lip that stopes it coming into the main case, so in effect was now floating instead of being fixed.
Replacement cases and macining £300, a fabric crank with primatist rod with vat was around £600 then all new bearings another 100
I've learnt my lesson for sure.
Polini spec for timings were 131 transfers all the same height for A B and boost port and 190 for exhaust wich ended up at 192 to suit the pipe, the head is spigoted into the barrel
I've not done the sta as im inherently lazy
My porting the barrel to get the bridged exhaust to get the port ends in a non linear path so the port edge went into the barrel with the sort of scoop that's better for flow was very limited bt barrel studs which also make the transfers narrower than they should be
I'm not equipped to do anything inside the bore either and don't have the knowhow so I think I'll leave that alone, plus my polini kit is no longer made as they are now 60mm bore and are now allowed in 152cc form for racing.

The plug in my lambretta head is shit too with it being too short for the b9egv plug, usually on all my othe heads the non thread part of the plug sits flush with the combustion chamber but on this on its like a mm short, it's also an offset plug and has a chamfer on the combustion side, seems OK with no plug washer a bpr9es is better to get the spark further in, ive never tried to use a plug without a washer so don't know the outcome of what would happen if I did, why the offset plug with a center squish I have no idea, original lambretta heads have an offset plug too but also a side squish

[wobbly]

We won 4 SKUSA titles with no plug washer, and as a by product I could index the plug much easier.

[lohring]

Model boat racers have used flow meters for years to set needle valves. They should work equally well for carb jets. Below is a diagram and picture. The flow rate of propane through a regulator is measured. We used 40 inches of water as the propane pressure.

Lohring Miller

[F5 Dave]

No a bad sort of yootoobe in TPI.


https://youtu.be/SIk-a8rdg6g?si=ZSaK4UPMS_yc3oR7

Bonus footage of Neil and Rob using the ESE dyno.

[diesel pig]

No a bad sort of yootoobe in TPI.


https://youtu.be/SIk-a8rdg6g?si=ZSaK4UPMS_yc3oR7

Bonus footage of Neil and Rob using the ESE dyno.

Beat me to it.

[Frits Overmars]

No a bad sort of yootoobe in TPI.

https://youtu.be/SIk-a8rdg6g?si=ZSaK4UPMS_yc3oR7
Bonus footage of Neil and Rob using the ESE dyno.354845 354846
Not my pictures, but I felt I should borrow them.

[Jonny snatchsniffer]

We won 4 SKUSA titles with no plug washer, and as a by product I could index the plug much easier.
That's interesting to know, did you use any kind of sealant on the thread or the face of the plug?
Did you notice any difference in power with doing so?

[wobbly]

On the dyno with no washer and the plug indexed it was a repeatable 0.3 Hp, in 40Hp - no sealant , just cranked it up R7376-10.
Probably as much due to the com increase as much as anything.
I data log checked and this translated into a lap reduction of around 2/10sec. But this was also checked for fun against a BR10EGV , and that was easily 0.5 sec slower.

[Storbeck]

A question for Frits, or anyone else familiar with this.

Apologies for asking a question that has almost certainly been addressed before but I have searched and searched and not found a definitive answer.

The shape described by the FOS port shape concept, this is NOT the shape of a template as it would be wrapped around the cylinder wall, this is a flat cross section that would need to be "projected" onto the curved wall. Correct?

And then would it be projected straight onto the wall, or would it be projected at a downward angle as the port is angled downward?

[Frits Overmars]

The shape described by the FOS port shape concept, this is NOT the shape of a template as it would be wrapped around the cylinder wall, this is a flat cross section that would need to be "projected" onto the curved wall. Correct?
And then would it be projected straight onto the wall, or would it be projected at a downward angle as the port is angled downward?Correct, Storbeck. The FOS port shape concept shows a flat cross section that is projected onto the cylinder bore, perpendicular to the bore axis.

[husaberg]

A question for Frits, or anyone else familiar with this.

Apologies for asking a question that has almost certainly been addressed before but I have searched and searched and not found a definitive answer.

The shape described by the FOS port shape concept, this is NOT the shape of a template as it would be wrapped around the cylinder wall, this is a flat cross section that would need to be "projected" onto the curved wall. Correct?

And then would it be projected straight onto the wall, or would it be projected at a downward angle as the port is angled downward?


Correct, Storbeck. The FOS port shape concept shows a flat cross section that is projected onto the cylinder bore, perpendicular to the bore axis.

I am not sure if I understood the last bit but I remember this bit

The exhaust port isn't canted downward 30°. The flange mounting face is canted downward 30° but the roof of the exhaust duct exits the cylinder at 25°.
The reason is that this angle gives the best flow.

The power valve starts opening at 10,000 rpm and it is fully open at 12,000 rpm. It can keep up with acceleration in any gear. And when you blip the throttle in neutral, the power valve servomotor moves almost as quickly as the revcounter needle.

[wobbly]

The projected shape onto the bore generates the chordal area - this is basically useless for any enlightening analysis , it just guides you toward what are the best physical dimensions at the bore face.
But the Effective Area , that then includes the Cosine of the down angle of the port Chordal Area then generates the STA, when rpm is factored in as well.
This combination of Chordal Area /Cosine / RPM can then be used to create an accurate indicator that will enable the user to hone in on the best really meaningful compromises that are required for their specific project end use.

[Frits Overmars]

The FOS port shape concept has one primary purpose: to keep the piston ring alive.
In addition, it can be used to optimize the blowdown angle.area for any given exhaust port height.

[wobbly]

To be clear Frits I was in no way making any criticism , just stating that your neat guide gives anyone the optimum geometry for the port shape only.
And yes it does generate the maximum chordal blowdown angle area for any predetermined timing, but even that cannot be " used " as this then has to modified to include the duct down angle
thus giving what is actually the point of the whole exercise - the Port Effective Angle Area.

[F5 Dave]

Well it's been a while, and Friday has passed, but this is kinda my Jam. Friday night music.

Throwback. Man I love redhead lasses.

Time for some religious music. Kinda.


https://youtu.be/9ipCKIxdHTs?si=HGdSCcp9kLbKjlIy
https://youtu.be/9ipCKIxdHTs?si=HGdSCcp9kLbKjlIy

https://youtu.be/9ipCKIxdHTs?si=HGdSCcp9kLbKjlIy

[koba]

Hey Team,

I used to post here a bit but sadly my attention has been diverted elsewhere for many years.
On and off I do try to catch up and thoroughly enjoy all the wisdom shared and great banter etc.

So, thanks to all of you who do contribute and make it such a cool place!

One thing I've managed to do as one of my many, many side projects is to put together a TF125 engine as a basic bucket build.
It was really fun and I challenged myself to keep it as simple as possible, minimal fancy tools etc.

It's turned out pretty well so far, the feedback from the riders is very positive.
The bike isn't finished yet, needing a shorter pipe to put it all together but even so it's done well and goes bloody good.

Enjoy :drinknsin
I'm sure I'll get some feedback on things I've got totally wrong in there :laugh:
Do let me know if there is anything obviously dumb etc. as I'll fix it up so it doesn't put anyone astray.

https://www.bucketracing.org.nz/tf125build

[wobbly]

If you are going to actually build a pipe at some stage I dont get why you are even considering using a design that is so obviously flawed.
The only reason it would be " insensitive " is because the engine is making bugger all power.
Post the .pack file on the site and I will help with something a bit cleverer.

[koba]

If you are going to actually build a pipe at some stage I dont get why you are even considering using a design that is so obviously flawed.
The only reason it would be " insensitive " is because the engine is making bugger all power.
Post the .pack file on the site and I will help with something a bit cleverer.

That would be awesome!

I had one already built on another bike so was just trying to get a quick result, still never managed to test it before moving though.

I'll try get hold of the .pack file, I accidentally left it on the wrong drive on the other side of the world.

[jonny quest]

The magnetic ignition trigger, which in my case is round. Is the middle of this trigger supposed to line up with the trailing edge of flywheel pad at .020" before TDC?
Retrofitting a YZ250 ignition system on something else and just need a starting point.

[wobbly]

Alignment of the lobe trailing edge and the center of the pole is used by aftermarket CDI. The stock ignitions have a timing line on the rotor
that aligns with a small raised marker line on the case - each one has a differing set angle at this point.
You would need to strobe it to find out what rpm they align , and check with a protractor or dial to see what static that represents on the 250.
Some factory manuals show the curve and state the static angle the lines align at.

[jonny quest]

Long story short, I put a YZ250 ignition system on a CR250. I have no reference lines.

It ended up being pretty easy to set timing. I initially guessed at it being retarded. I then rode bike and kept advancing it until it stopped accelerating harder off bottom.

I'll dyno it for best performance later, then mark cases, flywheel and stator for future.

It actually runs really good with just seat of pants tuning so far, and starts really easy. I must have done something right.

[TZ350]

.
A hole in one .....

354865 354866

I always kinda thought that the runs on the dyno were to short for any serious trouble but I was wrong, again!

[F5 Dave]

Weight loss program for reciprocating parts. ;)

[wobbly]

Easy to check the CCR now , bonus.

[Wos]

😞...let us learn from 😉 ...what was the reason in your case?

Remember that picture...in our case four mistakes

Dyno load was kept to high, for to long time.

Ignition at peak to early

Powerjet to lean

Thanks! 😉

Wolfgang ✋️

[Frits Overmars]

Dyno load was kept too high, for too long time.
Ignition at peak too early
Powerjet too leanAnd in addition, or maybe instead of all of the above:
How thin was that piston crown?
To be safe, it should be 15% of the bore. Judging from the above picture, it was not even half of that.
In a foul-stroke you might have gotten away with it. But not in a two-stroke.

[jonny quest]

And in addition, or maybe instead of all of the above:
How thin was that piston crown?
To be safe, it should be 15% of the bore. Judging from the above picture, it was not even half of that.
In a foul-stroke you might have gotten away with it. But not in a two-stroke.

As someone who works with both 2 and 4 stroke engines... it's amazing to me how much more complicated a 4strk piston is.... and how much lighter they are than a 2 strk piston.

A 2 stroke definitely needs thicker crowns.

[wobbly]

You are onto it as usual Frits , when I first tried the semi flat top piston design in a TM the 4* conical stock piston had an 6mm dome with 3 x 2mm ribs = 15%.
I machined 1.2mm off it to achieve the 38mm Diameter 50% area flat.
That worked on the dyno to test the viability and Hp potential of the head designs, but at the track the dome sunk 1.5mm in the middle the instant it went over 620*C
with 5 full power gear changes ( our normal best power egt at the time ).
Once the com had been automatically reduced it was fine , but now of course - slower.

[lodgernz]

.
A hole in one .....

354865 354866

I always kinda thought that the runs on the dyno were to short for any serious trouble but I was wrong, again!

Jeez that crown is awfully thin.

[husaberg]

Jeez that crown is awfully thin.

I looks like its been nibbled a way a bit by the ignition bunnies

And in addition, or maybe instead of all of the above:
How thin was that piston crown?
To be safe, it should be 15% of the bore. Judging from the above picture, it was not even half of that.
In a foul-stroke you might have gotten away with it. But not in a two-stroke.
That second picture seems to show its a lot thicker than it seems in the first.

https://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=354866&d=1722920360

[Wos]

I ve forgotten to list our fifth reason for melting the piston.

We converted a yamaha wr 125 enduro to a yz125 cross konfiguration but kept the spring of powervalve of enduro that opend valve later...that leeds to higher compression in high revs

All in all small misstakes ;)

All points fixed now and bike is running like never before 😉😘

Grüße Wolfgang

[Frits Overmars]

You are onto it as usual Frits , when I first tried the semi flat top piston design in a TM the 4* conical stock piston had an 6mm dome with 3 x 2mm ribs = 15%.
I machined 1.2mm off it to achieve the 38mm Diameter 50% area flat. That worked on the dyno to test the viability and Hp potential of the head designs, but at the track the dome sunk 1.5mm in the middle the instant it went over 620*C with 5 full power gear changes ( our normal best power egt at the time ).
Once the com had been automatically reduced it was fine , but now of course - slower.That's what got me thinking back in the day. In the 1980s the piston crowns of Jan Thiels unbeatable Garelli twins (six straight world titles) adjusted themselves just like you described. But I think it made the bikes faster rather than slower. In any case it made them overrev easier and every rider likes that.


I ve forgotten to list our fifth reason for melting the piston. We converted a yamaha wr 125 enduro to a yz125 cross konfiguration but kept the spring of powervalve of enduro that opened valve later...that leads to higher compression in high revsTo be pedantic: it leads to a higher effective compression ratio but not necessarily to a higher compression pressure because the pipe will have a word or two to say about that, and with the power valve lowering the exhaust port, the pipe will receive less exhaust gas energy to work with.
The late opening of the powervalve may well be a major problem cause, but for a different reason: it reduces the blowdown angle.area, so at high revs hot combustion gases will enter the transfer ducts and drastically raise the cylinder temperature. And when the cylinder gets hotter, so will the piston.

[wobbly]

Right again Frits , in the two projects I have done recently , both using PV that close all 3 ports , it was a real balancing act to adjust the ignition and the PV height to prevent detonation
in the mid range. In the sim you can see the huge trapped pressure in the cylinder created if the PV is too low.
This may in fact make more power at that point, but with the TubMax ( temp of the trapped unburnt squish gases ) thru the roof , destructive deto is inevitable, and difficult to control.
The KZ overeved better as well , but though it gained about 400rpm in the top it lost more than a useable 1000 rpm on the bottom off slow corners.

[Wos]

Dear Frits, dear Wob,

Think diffrence opening of powervalve was only about 1000 reves...yes effektive pressure counts there... but i think that was not MAIN reason for failure

All togther was reason ;)
AND
We tuned ignition peak by riding on the fields...rider had only chainsaw reve measurement , his eyes and feeling at his ass 😉...before we went to dyno ..and he felt peak only about 900 to late... this was the reason we set at powerpeak 3 degree to early ignition :(... thats realy a lot to early at this point especially if you have good filling there😮

Grüße Wolfgang ;)

[41juergen]

[QUOTE=wobbly;1131227467]Right again Frits , in the two projects I have done recently , both using PV that close all 3 ports , it was a real balancing act to adjust the ignition and the PV height to prevent detonation
in the mid range. In the sim you can see the huge trapped pressure in the cylinder created if the PV is too low.
This may in fact make more power at that point, but with the TubMax ( temp of the trapped unburnt squish gases ) thru the roof , destructive deto is inevitable, and difficult to control.
@Wob: thank's agin for that feedback, when I played around exactly that happened and after all the leassons learned from you, I went the right pass to cure that... :niceone:

[lodgernz]

I see that Alex Degnes ("2-stroke Stuffing") bike "Moped Dick" was the second fastest 50 at Bonneville, at 133kph (81.978mph)

[Peter1962]

I see that Alex Degnes ("2-stroke Stuffing") bike "Moped Dick" was the second fastest 50 at Bonneville, at 133kph (81.978mph)

Congratulations to that ! :headbang:

I sure hope that Alex returns to being active on the forum.

[diesel pig]

133 Kph is very good considering how thin the air is in Bonneville which affects non turbo and non supercharged engines quite badly I understand.

I look forward to his youtube video about his time there.

[lodgernz]

133 Kph is very good considering how thin the air is in Bonneville which affects non turbo and non supercharged engines quite badly I understand.

I look forward to his youtube video about his time there.

Yes, not a bad speed for normally aspirated and unstreamlined. The 50 that was about 6mph faster was in a different class, so who knows what that would look like.

[diesel pig]

Yes, not a bad speed for normally aspirated and unstreamlined. The 50 that was about 6mph faster was in a different class, so who knows what that would look like.

That's right it is not streamlined. That would here a big effect on the speed.

[diesel pig]

That's right it is not streamlined. That would here a big effect on the speed.

I remember reading in John Robinson's book on MC Chassis just how bad aerodynamics on MC's were, even with fairings on, they have bad aerodynamics. ironically there power to weight is fantastic.

[F5 Dave]

It is a lie down bike from what little I've seen.
A Freetech 50 in that chassis would murder it.
Local NZ (Faired but not fill streamliner) is 149km
Not trying to knock. He's only gaining info ATM.

[SwePatrick]

Friday!
Weekend, pop a beer and enjoy!



https://youtu.be/dacMUrzxh_Y

[adegnes]

We almost got the bike working reliable enough, but not quite.

First run on gas, 73mph. Far too rich, egt stabilized at 870f. This was with a 24mm PWK, 105 main jet.
Bonneville sits at about 4200ft/1250m, same elevation as Mack Colorado where we did some testing beforehand(not nearly enough, the engine was falling apart and most of the week was spent doing repairs).
4200 is bad already, but with the extreme heat, and humidity things get much worse. You get effective elevation printed on the timing slip after a run, our runs were done at an equivalent to over 8000ft/2400m.

Stupid as I am I didn't bring any smaller mains than 100.
Switched to a 28mm pwk with that 100 jet, as lean as we could go, and did another run. 82mph.

Egt still low at 1050f. Running 116 leaded.

Both runs done early in the morning.
Hard to find small pwk main jets in the pits, no way to go leaner.

Switched over to methanol and 30% nitromethane through a 35mm alcohol pumper carb.
Running this carb/fuel combo was the initial plan, but a clogged tank vent fooled me into thinking it didn't work too well. Didn't realize that vent was glogged until Bonneville tech inspection when demonstrating how our fuel shutoff solenoid worked.

Had a few failed runs were the bike would not rev, and just die after taking off.
The rotary valve was failing, so was that fuel solenoid.

Didn't bring a spare RV of course. Made new one out of a saw blade.
Bypassed the solenoid.
Bike seemed to run good on our roller in the pits.
New run. Seized 10s in. Too lean. Plug/piston top had started melting.
Salvageable.

New ring, dialed in lots more fuel. Back in line, last run.
Warmed up, stalled, then wouldn't run at all, RV had shifted on the axle and was now almost timed 180deg out...
Track closed.

354899


Notice the low temperatures. Also notice how stable the variator keeps rpm.
If only I had time before this to dyno it properly and figure out where peak power is actually sitting. There's a new pipe on it. Simulations say about 15500.
Installed a brake caliper for locking the gear ratio, but it had too much flex to work properly. Plan was to feel where power was sitting with that brake and adjust variator accordingly.

Also we might be running out of gear.

Being Norwegian I'm not used to the extreme heat. Felt like I was operating at about 20%. One day I drank roughly 15l of water and didn't pee once!

Hoping to be able to fly over sometime soon, fix the RV and get an unofficial record run done in Mack.

Questions:
- Could the friction disadvantages cancel out the flow advantage of a rotary valve vs reed in small engines like a 50?
There's so little torque, and very high rpm.

- pop off and fulcrum height in pumper carbs. I'm thinking I want to set this so that both high/low needles work in their normal range, no more than 3 turns out or so. Correct? Probably want really low pop off with a 35mm carb on a 50.

[adegnes]

Must add that the engine in use is very much a conventional specimen, and does not invole any of my usual free jazz experimental features.

Iame M50 cylinder(you might remember it) ported to rsa-ish spec.
Normal RV case induction.

[adegnes]

Moped Dick.

354900

[adegnes]

I'm sorry to say that Mark Atkinson "makr" passed earlier this year.
Head injury from motorcycle accident. Seemed fine, then died a few days later.
I was just about to ask him if I could come by his shop in Salt Lake when I heard.
RIP.

354901

[F5 Dave]

Hey good to see you post again. I tap on my phone in a cafe at a comfortable temperature. I salute you for your efforts. No one ever seem to crack a decent run without several visits. Best of luck.

[diesel pig]

I just watched your video of your time on the salt. adegnes, and it's ever what you think is going to be the problem that turns out to be the problem after seeing others time on the salt. Remember in the movie "World's fastness Indian" it turned what was eight trip's to the salt into one trip for the movie.

[husaberg]

I'm sorry to say that Mark Atkinson "makr" passed earlier this year.
Head injury from motorcycle accident. Seemed fine, then died a few days later.
I was just about to ask him if I could come by his shop in Salt Lake when I heard.
RIP.

354901

Bummer he was a talented dude. Speed of cheese will remain undefined

https://www.youtube.com/watch?v=pQQWhbSgv5w
https://www.youtube.com/watch?v=IfXNADcoMTs

[crbbt]

Quick question.

Will a single Det sensor pick up detonation on all cylinders in a multi cylinder engine?

I am planing on using a stud mounted sensor on the NX5.
I haven't found a two channel det sensor.
So I was going to mounted it to the cylinder which uses the leaner jet.

[41juergen]

Company April Sytems out of UK has a setup for 2 cylinder bikes...

[crbbt]

thank you!

[wobbly]

You can mount a det sensor on each head and run the signal wires to a 2 pole/2 position switch mounted on the bars or the dash.
The switch output then goes to det sensor input, means you can select what head to monitor.
Why are you running one cylinder leaner - it is alot better ( more power ) to change the ignition timing to end up with equal jetting, as the cause of the difference in the V Twin Yamaha engines is that
the case volumes are not the same , the intake lengths are different and the pipe shapes are also not the same.
In the 3YL/4DP it needs + 2* on the LH side.

[Tim Ey]

Why are you running one cylinder leaner - it is alot better ( more power ) to change the ignition timing to end up with equal jetting, as the cause of the difference in the V Twin Yamaha engines is that
the case volumes are not the same , the intake lengths are different and the pipe shapes are also not the same.
In the 3YL/4DP it needs + 2* on the LH side.
So which side has the longer intake and which side has the lower crankcase volume?

On the RGV250, the LH cylinder has the shorter inlet and the higher CR. Also 10 numbers higher mainjet.
So I assume you would increase ignition timing on the leaner side and adapt jetting?

[wobbly]

I dont think it matters what the cause of the jet split actually is - I decreased the timing by 1* on the RH side and it halved the EGT difference but power dropped.
So that direction wasnt optimum - I then reset the RH to zero and added 1* to the LH side , again that halved the split and power went up , and then with 2*added the EGT,s were around 10* different up to peak power
and they came together after PJ switching in the overev.
This need a small split of one size in PJ to get equal temps up the front side , and then equal EGT as before when they were switched off ( power on ) past peak.

[Grumph]

A guy I know spent hours equalising the case volumes on an '88 RS250.

Such is progress it's now possible to do effectively the same thing electronically.
And probably better.
thanks Wob.

[adegnes]

Wobbly, for peak power in a 50, how does reeds compare to RV with all clever reed-tricks applied?
I have a suspicion there's a point when going down in cc where friction cancels out the benefits of RV.
Wishful thinking maybe, it would be nice to not have the carb sticking out the side of the bike without having to resort to flappy belts or bevel gears.

Tried the 11yr Lagavulin Offerman? Not too bad! Then again it's hard to find a bad Lagavulin...

[crbbt]

I had never questioned why the jetting was different between the cylinders.

Looks like I'll be slotting one of the pick up!

or buying an expensive ignition

[koba]

I had never questioned why the jetting was different between the cylinders.

Looks like I'll be slotting one of the pick up!

or buying an expensive ignition

Buy a good ignition, in context this is very cheap.

[wobbly]

Two issues - in the case of reeds the crankcase volume is a " tuneable" element up to a point.
A bigger case ( and its associated Helmholtz frequency ) needs to be paired with a thinner petals higher 1st Mode frequency.
This works really well in that power rises , up to a point where the petals reduced stiffness in cantilevered bending causes loss of control at higher rpm
and then power drops - dramatically.

I tested this to death in the KZ , by making a small 1/2 moon cutouts in the petal sides up near the clamp, in 0.1 mm increments of depth.
With each subsequent increase in depth the now softer petal made more power everywhere - up to a depth of around 3mm/side.
At this point I had an extra 1.5 to 2 Hp up the front side and about 1 Hp at peak.
At 3.1mm depth suddenly the peak and overev power dropped hugely.
I now have a tape on gauge plate as a guide to the exactly correct depth to Dremmel.

At the same time as I was testing the petals I played with case volume by machining 5 mm off the reed block mount face on the case.
Running the now smaller case volume it lost power everywhere , and I only gained back 1/2 the loss by going 0.12mm thicker with the petals.
Then I went bigger in volume by adding a 10mm spacer plate - this lost power as well , so I started first with softer petals , then the side cutouts.
But it very soon hit the wall with reed flutter and I could never get back the power seen with a stock case volume.
That volume gave a ratio of exactly 1.3 - and so it seems that for a wide range of engine displacements that ratio is the baseline to start experimenting with.

The second issue is the superiority factor or Rotary Vs Reeds. Again I have tested this in a 125cc engine that was available in both configurations and had identical cylinder stud fixing.
After optimizing the Rotary with a carbon valve and using HPC friction coatings and CNC cut indentation cutouts on both the cover and case face , it ended up making around 3.5 Hp more than
the reed version after that to was optimized using the modified petals at 1.3 case volume.
The rotary ended up down at 1.22 case volume , and I went bigger by machining the case around the outsides of the flywheels to achieve 1.2 ratio but it then lost a bunch of front side
no matter what valve closing was used , so I had to machine a ring and weld it back into the case to get back to 1.22 ratio.
The rotary made just on 46 Hp at the time so it was about 7.5% better than I could achieve with the reed using the same cylinder and pipe.
I do wonder now if , using EngMod , I could optimize both and maybe get a closer result , but although I have developed better reed stuffers , and of course way better pipes, I think the newer elements
of pipe design would still put the rotary ahead by a desirable margin.

Thus in answer to the idea about ignoring different case volumes in a twin and reducing jet splits with timing changes - I believe that there will be an optimum case volume in each scenario
and using that will make more power than the compromise of changing the EGT by splitting the timing.
Other elements such as intake length and pipe configuration differences can be ameliorated way more easily by ignition fiddling.

Plus in a 50cc you are going to have to be reving it to at least 16,000 to gain maximum benefit of sonic tuning , and as usual I would bet the friction goes up as the square of rotational velocity.

[adegnes]

Thank you! What would the world be without you doing the 0.1mm reed cutting work.

I ran my (too)experimental engine with a timing belt primary to a jackshaft in place of the crank in an am6 engine on my inertia dyno.
2:1 primary gave 13.3hp, 1:1 gave about 6.
I did the runs in different gears to have the same acceleration of the roller.
Where did half the power go?
My guess is friction.
There's so little torque produced.
Peak power was at about 17k rpm.
26hp without the dual primaries? 😁

[Wos]

Alex Denges?

Which Material pairing do you have in your rotary valve?

There are so many diffrent coatings available today which reduce friction to 1/2

For example hard coatings that are filled with ptfe, graphite or MoS2 for steel or aluminium.

And many spray coatings for diffrent special use.

Finding optimum pairing and you can drop friction further more 😉

Good luck!! 😀

Grüße Wolfgang

[adegnes]

Alex Denges?

Which Material pairing do you have in your rotary valve?

There are so many diffrent coatings available today which reduce friction to 1/10

For example hard coatings that are filled with ptfe, graphite or MoS2 for steel or aluminium.

And many spray coatings for diffrent special use.

Finding optimum pairing and you can drop friction further more 😉

Good luck!! 😀

Grüße Wolfgang

Yep, that's me👍

I've mostly used carbon fiber in aluminium housing. With methanol/nitro I'll use steel valves from now on. Methanol leaches into the resin and softens it, happens pretty fast.

I'll do some coating research, thanks!

[Wos]

Alex,

Corrected my Statement down to a half, because lubricated conditions.

Ptfe to steel pairing is hard to beat with 0.04... dont know if dlc ( diamond like carbon) coated steel rv will bring further big advatages, cause the load is small, there are no abrassive conditions... i hope no sands or salt is involved!! 😉 😀
Are there signs of wear alex?

Surely carbon fibre is not best pairing to aluminium...fibres can be abrassive...frits and jan did a special coating of the case..

But maybe its better to coat rv and case...or searching for carbonfibre that is filled or coated with petfe...
Or do a complete insert of pure ptfe to the case...

Highly complex and interesting thing 😉

Grüße Wolfgang

[adegnes]

Alex,

Corrected my Statement down to a half, because lubricated conditions.

Ptfe to steel pairing is hard to beat with 0.04... dont know if dlc ( diamond like carbon) coated steel rv will bring further big advatages, cause the load is small, there are no abrassive conditions... i hope no sands or salt is involved!! 😉 😀
Are there signs of wear alex?

Surely carbon fibre is not best pairing to aluminium...fibres can be abrassive...frits and jan did a special coating of the case..

But maybe its better to coat rv and case...or searching for carbonfibre that is filled or coated with petfe...
Or do a complete insert of pure ptfe to the case...

Highly complex and interesting thing 😉

Grüße Wolfgang

Steel valve + full ptfe inserts sounds like a good plan.
I saw considerable wear to both the carbon fiber valve, and 7022 alloy cover.
Made a wear surface in the cover from hardened steel(saw blade). Shortly after the disc exploded, probably softened/weakened by methanol.

I'm designing a new case and cylinder for the landspeed bike, easy to implement room for ptfe inserts.
Nothing experimental, shameless RSA copy, normal rotary valve intake.
Probably higher rpm than the norm, but most people seem to try to get power out of a 50 at idle speed.

Experimental and/or good-enough-for-testing-purposes does not work for actual racing. Who would've thought...

354917

Molds will be 3d printed in sand and cast by Zalewatec in Germany.
Here's a little metal pouring trick on their Instagram:
https://www.instagram.com/reel/C4DZNy6sTjp/?igsh=MWN1aXRsZTZjbGx0Zg==
354918

A hand operated valve in the pouring basin, clever!

[Rudex]

Steel valve + full ptfe inserts sounds like a good plan.
I saw considerable wear to both the carbon fiber valve, and 7022 alloy cover.
Made a wear surface in the cover from hardened steel(saw blade). Shortly after the disc exploded, probably softened/weakened by methanol.

I'm designing a new case and cylinder for the landspeed bike, easy to implement room for ptfe inserts.
Nothing experimental, shameless RSA copy, normal rotary valve intake.
Probably higher rpm than the norm, but most people seem to try to get power out of a 50 at idle speed.

Experimental and/or good-enough-for-testing-purposes does not work for actual racing. Who would've thought...

354917

Molds will be 3d printed in sand and cast by Zalewatec in Germany.
Here's a little metal pouring trick on their Instagram:
https://www.instagram.com/reel/C4DZNy6sTjp/?igsh=MWN1aXRsZTZjbGx0Zg==
354918

A hand operated valve in the pouring basin, clever!

You should try this mod on cylinder and experiment.

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131221111#post1131221111

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131221113#post1131221113

Or you can do with insert 3d parts like you were doing.
Regards-

[adegnes]

You should try this mod on cylinder and experiment.

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131221111#post1131221111

https://www.kiwibiker.co.nz/forums/showthread.php/86554-ESE-s-works-engine-tuner?p=1131221113#post1131221113

Or you can do with insert 3d parts like you were doing.
Regards-

So Rob has been playing with the trapped ring/huge port concept👍😊👍
I'm a few hundred pages behind, reading up as fast as I can!

[adegnes]

354919
McMurray Tri-Mac Speedsters Supercharged 100cc opposed piston uniflow two stroke. Pretty cool!
Some info on the bike in my video from Bonneville.
Two opposing Honda 4t 50s with a custom cylinder in between, AMR300 blower, megaphone pipes.

Running mechanical injection, methanol/nitro. Had pump issues at the salt.

[Wos]

Steel valve + full ptfe inserts sounds like a good plan.
I saw considerable wear to both the carbon fiber valve, and 7022 alloy cover.
Made a wear surface in the cover from hardened steel(saw blade). Shortly after the disc exploded, probably softened/weakened by methanol.

I'm designing a new case and cylinder for the landspeed bike, easy to implement room for ptfe inserts.
Nothing experimental, shameless RSA copy, normal rotary valve intake.
Probably higher rpm than the norm, but most people seem to try to get power out of a 50 at idle speed.

Experimental and/or good-enough-for-testing-purposes does not work for actual racing. Who would've thought...

354917

Molds will be 3d printed in sand and cast by Zalewatec in Germany.
Here's a little metal pouring trick on their Instagram:
https://www.instagram.com/reel/C4DZNy6sTjp/?igsh=MWN1aXRsZTZjbGx0Zg==
354918

A hand operated valve in the pouring basin, clever!

Hey Alex,

Maybe a paper air filter could help...dont know your configuration

Saw blades are made of HSS in most cases 😉

Very hard and wear ressistant material cause of tungsten or vanadium carbides in the matrix.

These carbides, seen under microsope, can built a rough surface...very hard small peaks standing out of surface...nearly impossible to polish well

I would choose a steel without... that is not forming carbides or nitrides...maybe rolled material...this is giving hard and elastic behaviour without carbon or hardening process

For example often feeler gauges are made of this Material 😉

https://www.hasberg-schneider.de/en/services/presision-thickness-gauge-strip-standard-dimensions/

Grüße Wolfgang

[wobbly]

Alex , I dont understand why you are sticking to the high Exhaust port floor concept.
The idea has been around for a while , but as I have stated before , to my knowledge no one has actually proven it works.
Jan lifted the floor 3mm on an RSA, and the dyno test was successful , and I have done the same on a TM KZ.
But his next experiment with it higher again , coincided with him retiring and the cylinder was machined back to stock before he left.

Thus you are flying in the dark - again.
Get the damn thing working perfectly as a somewhat conventional setup first I believe is the best approach.

At this point the Freetech 50 engines are light years ahead of you on petrol, and running reliably.
The other thing I noted somewhere is you said you were using C16 - this does not work well in a 2T.
It may have huge octane rating , but has minimal RVP - in fact in cold conditions it was found that the engines would not even start.
VP has a newer version that is specifically designed for 2T use.

[adegnes]

Alex , I dont understand why you are sticking to the high Exhaust port floor concept.
The idea has been around for a while , but as I have stated before , to my knowledge no one has actually proven it works.
Jan lifted the floor 3mm on an RSA, and the dyno test was successful , and I have done the same on a TM KZ.
But his next experiment with it higher again , coincided with him retiring and the cylinder was machined back to stock before he left.

Thus you are flying in the dark - again.
Get the damn thing working perfectly as a somewhat conventional setup first I believe is the best approach.

At this point the Freetech 50 engines are light years ahead of you on petrol, and running reliably.
The other thing I noted somewhere is you said you were using C16 - this does not work well in a 2T.
It may have huge octane rating , but has minimal RVP - in fact in cold conditions it was found that the engines would not even start.
VP has a newer version that is specifically designed for 2T use.

The picture is misleading wobbly. Exhaust duct floor is sitting just 1.5mm above bdc. I've gone 95% RSA copy, pretty much the only difference is duct exit which is reduced to same area as blowdown, 76% of total effective area in this case.
I'm keeping ludicrous experimental stuff out of this engine.


Was running c12 at Bonneville before switching to methanol/nitro. Would've been clever to switch out for something unleaded and highly oxygenated probably.
At home I've been running sunoco supreme.

I'll study fuel, thanks for the heads up!

[adegnes]

Renderings of the new engine.
RSA ports/ducts(more likely RSW, took measurements from drawings I could find on here and in what Frits sent me a while back). Exhaust floor 1.5mm above BDC.
Exhaust duct exit reduced to effective blowdown area, will have a transition in the flange spigot.
Cooling inside and over transfers, then under ex duct, over ex duct and into the head. Hopefully I can get the 3d printed sand out of there.

Least insane design so far😁

354921354922354923354924354925

[wobbly]

I have done a huge amount of testing around the Aux ducts and the entry to the main.
The floor should exit perpendicular to the bore then radius down as a ski jump.
The roof should go the other way , forming an area pinch point exactly where the side ducts enter.
This reduces the area change where the side ducts add into the main port , and anything shorter or longer than 12mm with the Aux septum looses power.

[F5 Dave]

Those measurements were a 125 yeah. so could he assume a 50 would scale down a touch? Obviously that would make his model worse still. At some point there needs to be metal enough to absorb the heat evenly. I guess thermodynamics care little about convenient scaling.

[adegnes]

Those measurements were a 125 yeah. so could he assume a 50 would scale down a touch? Obviously that would make his model worse still. At some point there needs to be metal enough to absorb the heat evenly. I guess thermodynamics care little about convenient scaling.

👍 Damn you thermodynamics!


I have done a huge amount of testing around the Aux ducts and the entry to the main.
The floor should exit perpendicular to the bore then radius down as a ski jump.
The roof should go the other way , forming an area pinch point exactly where the side ducts enter.
This reduces the area change where the side ducts add into the main port , and anything shorter or longer than 12mm with the Aux septum looses power.

Thanks for the advice! I'll get to work!

[Tim Ey]

Dont be too optimistic with the bridge thickness in casting. Either make them thicker in the addition that you will put on, or make them wider and grind them to suit.

What timings are you aiming for? I doubt that you will need ridiculous high timings for a peak at reasonable rpm.

[adegnes]

Dont be too optimistic with the bridge thickness in casting. Either make them thicker in the addition that you will put on, or make them wider and grind them to suit.

What timings are you aiming for? I doubt that you will need ridiculous high timings for a peak at reasonable rpm.

Crossing fingers! There's 3mm added to the bore in the model for casting.
I managed to successfully cast cylinders with the same bridge thickness at home. Did take me 6 tries , but was my first ever experience with casting.
Lost pla, sand/plaster mix.
Zalewatec thought it would cast well.

198ex + a little bevel
130A
132B/C
90mm rod, 39.3mm stroke.
STA matched in Engmod, lots of area.

Working on the pipe, I am looking for relatively reasonable rpm.

[ken seeber]

Alex,

Re your concerns re possible frictional drag of the disk valve. I agree with others (Wos) that this might be small, given the right material matching. However, I am aware of these breaking (in karts) occasionally and your experience.

So, how about eliminating the friction entirely? Instead of allowing the valve to “float” axially within the valve housing (presumably bearing on either side of the valve depending on the pressure differential between the crankcase and the intake system), fix the valve to the crankshaft so it cannot move axially. Then adjust the side clearances between the disk and the cover, such that the disk cannot contact (drag) the cover. Obviously to do this will require allowance for crank float and thermal expansion of the cases etc. To make you feel better, a more solid disk, eg 2 mm steel to remove and doubt about bending.

Yes, yes, I know there will be leakage, loss of sharp timing and maybe even hard to start etc, but does this matter? Remember 24/7 induction, open all the time, making any such leakage relatively minor.

Keep up the 2 stroke passion.

[Wos]

Alex,

Re your concerns re possible frictional drag of the disk valve. I agree with others (Wos) that this might be small, given the right material matching. However, I am aware of these breaking (in karts) occasionally and your experience.

So, how about eliminating the friction entirely? Instead of allowing the valve to “float” axially within the valve housing (presumably bearing on either side of the valve depending on the pressure differential between the crankcase and the intake system), fix the valve to the crankshaft so it cannot move axially. Then adjust the side clearances between the disk and the cover, such that the disk cannot contact (drag) the cover. Obviously to do this will require allowance for crank float and thermal expansion of the cases etc. To make you feel better, a more solid disk, eg 2 mm steel to remove and doubt about bending.

Yes, yes, I know there will be leakage, loss of sharp timing and maybe even hard to start etc, but does this matter? Remember 24/7 induction, open all the time, making any such leakage relatively minor.

Keep up the 2 stroke passion.

Good idea 😉 worth to think... a 2 mm stiff disc out of titanium

Calculate max axial forces given at inlet by max pressure Differenz and max forces from moving mass of gases...

Maybe a physicist could do that 😀

Find max bending of titanium valve disc at these forces...do minimum possible spacing

[Tim Ey]

Crossing fingers! There's 3mm added to the bore in the model for casting.

In radius or diameter? In diameter it is not enough. I did the same and needed to weld.



198ex + a little bevel
130A
132B/C
90mm rod, 39.3mm stroke.
STA matched in Engmod, lots of area.
.

Matched sta or real study?
Since those are the RSA timings, I would think it will behave well at the same pistonspeed. That would be 17000rpm...

I think I would rather start at
A 126
B/C 124
MAIN 193
AUX 178
With a peak at 14500 and overrev to 16000

Grinding higher is easier than grinding down.

[adegnes]

Alex,

Re your concerns re possible frictional drag of the disk valve. I agree with others (Wos) that this might be small, given the right material matching. However, I am aware of these breaking (in karts) occasionally and your experience.

So, how about eliminating the friction entirely? Instead of allowing the valve to “float” axially within the valve housing (presumably bearing on either side of the valve depending on the pressure differential between the crankcase and the intake system), fix the valve to the crankshaft so it cannot move axially. Then adjust the side clearances between the disk and the cover, such that the disk cannot contact (drag) the cover. Obviously to do this will require allowance for crank float and thermal expansion of the cases etc. To make you feel better, a more solid disk, eg 2 mm steel to remove and doubt about bending.

Yes, yes, I know there will be leakage, loss of sharp timing and maybe even hard to start etc, but does this matter? Remember 24/7 induction, open all the time, making any such leakage relatively minor.

Keep up the 2 stroke passion.

Thanks Ken, that is worth a try.
I'll keep to the tried and true with my new engine for now, and experiment with stuff like that in parallel.
I've always wanted to try servo driven RV + rotary encoder on crank. Don't think I'm the only one who's had that idea, but I've never seen it done.

Speaking of experimental stuff.
I'm playing around with a brute force concept v2.
A pile driver diesel hammer/sleeve valve hybrid.

Maybe I should just go opposed piston uniflow.
Here's Tri-Mac Speedsters Supercharged 100cc opposed piston uniflow two stroke. Two Lifan engines with a custom cylinder in between. They're talking about it in my Bonneville video.

354933354932

[adegnes]

In radius or diameter? In diameter it is not enough. I did the same and needed to weld.



Matched sta or real study?
Since those are the RSA timings, I would think it will behave well at the same pistonspeed. That would be 17000rpm...

I think I would rather start at
A 126
B/C 124
MAIN 193
AUX 178
With a peak at 14500 and overrev to 16000

Grinding higher is easier than grinding down.

3mm radius, 34mm bore.
In my castings I made separate small feeders for all the bridges, then a big feeder for those feeders.

Current engine in the landspeed bike has a ported iame m50 cylinder with the same timings/angles, but not as much area. It works well, especially after I made a new pipe for it, the old pipe was made from pieces of a shovel, and some scooter pipe pieces.
Made 18rwhp with that old pipe, new pipe should give considerably more.
But.
The crank in it has too small webs, not enough material around the crank pin. Made even worse by the outer edges being beveled, and balancing holes too close. All available cranks seem to have the same issues.
My testing up until this year when I revived it(bike has been in the US for 5yrs)has been with those cranks running continuously in and out of true.
No wonder my fuel was foaming... Also explains why it ate two big end bearings for no apparent reason.
Welding the crank pin helped a lot.
It also suffers from high wear. Short 75mm rod, and cast iron bore.
I think piston slap is what caused it to pinch the ringland a few times, probably in combination with touching the head caused by the eccentric crank.

The reason for building a new engine is to fix all this stuff.
Plated bore vs cast iron, 90mm rod vs 75mm, beefier crank, and more port area as I'm not working within the confines of an existing cylinder.

[wobbly]

Tim Ey , but with a square bore/stroke and the same piston speed the 50cc engine will be operating at its most efficient at 17,000.
The only reason I would see that going down to 14500 rpm and an Ex port at 193* would be to accommodate a crap gear ratio set and needing a much wider power band
for say a Bucket racer - thats all been done before , and would never break any sort of records.
LSR has none of those limitations and needs as much peak power and overev as is possible, so it drops back into peak torque for the final gearchange with max aero drag.
Remember Power = T X RPM , reving the thing to its mechanical piston speed capability ,as long as the STA numbers match at that rpm, automatically approaches the theoretical maximum achievable

[adegnes]

Tim Ey , but with a square bore/stroke and the same piston speed the 50cc engine will be operating at its most efficient at 17,000.
The only reason I would see that going down to 14500 rpm and an Ex port at 193* would be to accommodate a crap gear ratio set and needing a much wider power band
for say a Bucket racer - thats all been done before , and would never break any sort of records.
LSR has none of those limitations and needs as much peak power and overev as is possible, so it drops back into peak torque for the final gearchange with max aero drag.
Remember Power = T X RPM , reving the thing to its mechanical piston speed capability ,as long as the STA numbers match at that rpm, automatically approaches the theoretical maximum achievable

Exactly ��
I'm running a variator and don't need the overev, just peak.
Said variator worked flawlessly out there, rock steady rpm.
The challenge is setting it right for a run.
We saw variations in relative density altitude(from under 5000ft to almost 9000ft throughout a day.
At high RAD(and jetted right) there's more power, and the variator will rev higher with the same weights/spring tension, at low there's the opposite.
Need a good table of what's needed, or a good automatic correction system.

I'm debating if I want to run methanol/nitro, or run gas through the carb and have a separate nitromethane injection system.
Did anyone ever try injecting nitromethane alongside a carb already tuned well on gas? No extra air, just the nitro. I know Rob has mentioned wanting to try a few times.

[wobbly]

My first reaction to the huge Density Altitude variations is that a Lectron is affected by this less than 1/2 a normal carb.
And several guys running Pikes Peak have used a simple hand operated lever to adjust a screw in PJ and watched the EGT during the run to keep it on the money.
But a way cleverer way is that used by Tillotson for their pumper carbs - they use a servo setup from the RC car world with either +/- on board buttons or even remote control for
the screw adjusters.
Even one step cleverer again would be to use the 0-5V RAD output from a digital weather station , programmed thru an Arduino or Raspberry device to auto correct the real time EGT input by controlling
the PJ servo on top of the carb.

[Grumph]

We seem to have come a long way from Hugh Anderson riding the works Suzukis using a combination of throttle and air lever...

Get it right and it would last a TT. Wrong and you're out

[F5 Dave]

I was going to write., satellite wifi link , connect egt, pj, det sensor, 6 axis IMU, pornhub, gambling account, bitcoin wallet, and finally throttle control to chat- gbt so it can decide and you aren't tempted to Pussy Out when you encounter a sidewind, loss of traction, or braking marker.

[adegnes]

I was going to write., satellite wifi link , connect egt, pj, det sensor, 6 axis IMU, pornhub, gambling account, bitcoin wallet, and finally throttle control to chat- gbt so it can decide and you aren't tempted to Pussy Out when you encounter a sidewind, loss of traction, or braking marker.

😂 Travis would appreciate chat-gpt serving him some porn.
354947

If nitromethane injection alongside a carb running gas works then fueling won't be a problem. On the fly variator tuning is probably necessary though, I'll leave that to the satellite link.

[diesel pig]

Rereading my posts on your time on the salt. I now realize I was coming across happy with your speed but what I was really happy about was you had done your first run on the salt (everything I have read about people's run on the salt was it was like running on nothing else one will run on ever) and now you could concentrate on your speed. Now my two cents on your intake thoughts, I think you should first make use of the fantastic information on this and other sites to build the best conventional 2T you can whether that is reed or disc for your speed runs. But ultimately I think the way you should go would be Frits's 24/7 inlet system but Free jazz* on that in between building a good conventional motor!

*I love that term and will use it where ever I can.

[Condyn]

With a CVT front side right before peak, peak, and a small bit of over rev are still important. I have made hundreds of tests on my cvt drag snowmobile and made and tested many pipe designs. The difference is my pipe temp never stabilizes in 500 feet where yours should be. Regardless, It is far more forgiving for your pipe to be designed to better handle even minuscule load changes, whether that be a bump in the track, or a slight elevation change, or in your case a gust of wind. The effect on peak is virtually non existent if done right. The clutch will do its job to hold rpm steady, but there is always going to be a small amount of load change. When watching DA, Knowing what your cvt needs is equally important as jet. Worse air, no power, less weight, less jet, slow ET/MPH etc. It will take a lot of testing time to figure out a scale so you know what to do. Once on your cherished run, there are curse words yelled when you know it is a waste of time because you have no rpm. Jet obviously has to be optimized before anything. It is a big circle of confusion because more clutch weight creates its own need for more fuel, so it compounds itself as the air gets better or worse.

[adegnes]

Here's the piston and plug from the landspeed bike after a run where it seized just 10s off the line.
Lean on Methanol/Nitro. You can see how the ground strap, center electrode, and piston dome has started melting. Good thing the crown grew too much and it locked up before we had alu dust everywhere.
Mixture seemed ok on our roller in the pits, obviously it wasn't. Did actually sound lean before take off, should have aborted.

354951354952

[Gradella23]

Here's the piston and plug from the landspeed bike after a run where it seized just 10s off the line.
Lean on Methanol/Nitro. You can see how the ground strap, center electrode, and piston dome has started melting. Good thing the crown grew too much and it locked up before we had alu dust everywhere.
Mixture seemed ok on our roller in the pits, obviously it wasn't. Did actually sound lean before take off, should have aborted.

354951354952

hello, what kind of piston is that? which compression heigth? I'm desperate for light and well manifactured 39,96 pistons

[adegnes]

hello, what kind of piston is that? which compression heigth? I'm desperate for light and well manifactured 39,96 pistons

Barikit PE-65, 0.8mm ring, ring gap centered over C port, 12mm wrist pin.
24.5mm compression height, 100mm dome radius.
Emot Racing has them sometimes, VRM in Sweden too. VRM just got more in stock.

[Gradella23]

Barikit PE-65, 0.8mm ring, ring gap centered over C port, 12mm wrist pin.
24.5mm compression height, 100mm dome radius.
Emot Racing has them sometimes, VRM in Sweden too. VRM just got more in stock.

same as me ahah, got it from martijn at emot. it's just a little bit heavy at 77g (with pin, clips and all).

[SwePatrick]

Dynoweekend in my garage, and with my TZR250(242cc)

Ask me anything about the setup, i´ll answer later on.

The setup:
1KT engine
Methanol M1
Lectron (39mm, modified high velocity to my own likings)
Ported Banshee Vforce 4 with 0.35 polini inner petals, and 0.4 polini on outer(oem vforce petals gets soft from methanol)
+5mm rods(RD350/banshee) TZ bigend bearing.
56mm modified Wössner pistons (YZ125 1989)
3xv cylinders, ported by me and adapterplate milled by me.
18-1 in compression
Pipes simulated in MOTA and built by me.
Welded and redesigned crankcase for better direct of flow.
Ignitionsystem is Maxxecu mini, running on a Makita 18v battery.(20.5v)

There might be some more power lurking(partly because i have setup my dyno restrictive), but i called it done, as it is long to next race season, probably need to re-dyno it coming spring.
So i save up on the running hours, as the engine is recently overhauled.

One luxury problem i have had, it lifted the heads earlier.
So i made sturdier studs for both heads and cylinders in toolsteel and heattrated them.
I also cut in a pianowire in the cylinders to give a very good mechanical head seal, since then, no more problems.

All work done by me.


Day one here:


https://www.youtube.com/watch?v=56nvZZnw8zI&t=507s

And day two here:


https://www.youtube.com/watch?v=cLWx7TKbD1c

[Gradella23]

Barikit PE-65, 0.8mm ring, ring gap centered over C port, 12mm wrist pin.
24.5mm compression height, 100mm dome radius.
Emot Racing has them sometimes, VRM in Sweden too. VRM just got more in stock.

hello alex, just for your info, I bought a malossi 34.8544 piston with 25mm compression height and 134 dome radius (circa- measured with the comprator on the cnc machine). It weights 74g, but using the barikit pin which has the conical shape of the hole, I dropped it to 71,4g. This is a 5,6 grams gain over the barikit kit. Not bad for a 50cc

[adegnes]

hello alex, just for your info, I bought a malossi 34.8544 piston with 25mm compression height and 134 dome radius (circa- measured with the comprator on the cnc machine). It weights 74g, but using the barikit pin which has the conical shape of the hole, I dropped it to 71,4g. This is a 5,6 grams gain over the barikit kit. Not bad for a 50cc

Nice! What thickness is the ring on that piston, and what sizes does it come in?

[adegnes]

I just discovered small RC hydraulic gear pumps is a thing.
https://goldlandrc.com/product/10mpa-high-pressure-hydraulic-gear-italian-oil-pump/
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Could maybe be used for electromechanical continuous fuel injection.
May not even need a barrel valve as the pump is independent from engine rpm.

I've ordered one, will give it a try. Already got some water injection nozzles that should work.
Will be tested independently on a known good engine this time:wacko:

[flyonly]

My first reaction to the huge Density Altitude variations is that a Lectron is affected by this less than 1/2 a normal carb.
And several guys running Pikes Peak have used a simple hand operated lever to adjust a screw in PJ and watched the EGT during the run to keep it on the money.
But a way cleverer way is that used by Tillotson for their pumper carbs - they use a servo setup from the RC car world with either +/- on board buttons or even remote control for
the screw adjusters.
Even one step cleverer again would be to use the 0-5V RAD output from a digital weather station , programmed thru an Arduino or Raspberry device to auto correct the real time EGT input by controlling
the PJ servo on top of the carb.

Wobbly

Which model carb would you choose to use?


Sent from my iPhone using Tapatalk

[wobbly]

Fly , depends upon the engine config and the end use.

[diesel pig]

Fly, I must say the more I find out about the lectrons. The more impressed I am with them. Especially with the modern ones.

[F5 Dave]

Ooh, let's play this game in reverse.

How about one of those tubes types where you wind a fuel damp wick into the airstream?

[Gradella23]

Nice! What thickness is the ring on that piston, and what sizes does it come in?

1mm ring, starts from 39.93 sel. 0 to 39.97 on sel. C, but at the moment it looks like the only two available are A and B (from 39.94 to .96)

[adegnes]

Continuous high pressure injection could be the ticket for higher nitromethane percentages. Better atomization, less fuel just passing through the engine unburnt.

Variated landspeed bike is a special use case. I need to be able to climb from somewhere early in the powerband to peak power rpm once, then steady state WOT at peak power rpm for 5km or so.

[husaberg]

Ooh, let's play this game in reverse.

How about one of those tubes types where you wind a fuel damp wick into the airstream?

everyone's wanting to build a better mousetrap...

https://youtu.be/kQXm_6EVgHY


https://youtu.be/yl1jxWPb-C0?t=237

[diesel pig]

everyone's wanting to build a better mousetrap...

https://youtu.be/kQXm_6EVgHY


https://youtu.be/yl1jxWPb-C0?t=237

I have have personally come a cross rats that I think would not be phased by a direct hit by the gun one.

[TZ350]

Continuous high pressure injection could be the ticket for higher nitromethane percentages. Better atomization, less fuel just passing through the engine unburnt. Variated landspeed bike is a special use case. I need to be able to climb from somewhere early in the powerband to peak power rpm once, then steady state WOT at peak power rpm for 5km or so.

My previous limited experience with a two stroke and Nitro on the dyno. Is that, it was good for additional low down torque and for filling in the hole just before getting up on the pipe. Once the engine started coming anywhere near maximum torque it was best to stop adding nitro. It sure looked like it would give the bike some extra lift coming out of corners. A real power band widener. It would be interesting to adjust the engines compression/ignition properly for Nitro. Maybe I will try it one day.


.
NITRO METHANE
.
Too days dyno experiments were with my Suzuki RG50 powered Bucket Racer and raw Nitro.

I have always theorized that with a correctly jetted two stroke running properly on race gas or similar one can just squirt raw Nitro Methane into the bell mouth and you will see a power increase with out any air fuel mixture issues. The reason is, that raw Nitro carries just a little more fuel than oxygen so as well as adding oxygen for more power it effectively richens the ingested mixture too.

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The experiment was a bit crude. Just squirted the Nitro in. Blue line is Av Gas only and correctly jetted for max power. The red line is with Av Gas and Nitro squirt. The red line shuts of early as it goes over rich. For Nitro to be useful you would need ignition and mixture control. So the conclusion is that with a digital ignition and power jet control Nitro could be a very viable option, pity Nitro is illegal in our racing class.

But anyway if you have ever wondered if Nitro could be a good thing with two strokes then this experiment suggests there are real possibilities there.

[136kg136ps]

So could a switched PJ be used to add the nitro at the desired RPMs?
I could see adjusting timing to coincide with the nitro but compression would be a bit beyond me.

[Frits Overmars]

pity Nitro is illegal in our racing class.Pity?
My limited experience with nitro dates from testing a blown dragster on nitro as technical editor / testrider for Moto73 in 1976.
My most vivid memory after all these years is not the acceleration, but the hellish pain when you get nitro fumes in your eyes.
I suppose inhaling the stuff can't be very healthy either. And if you don't care about the corrosion in your lungs, think about the corrosion in your engine.
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