ESE's works engine tuner [Archive] - Page 153

jfn2

31st March 2023, 07:01

Hello again Wobbly
I think I have my front and back walls for the 'A' transfer port mixed up. Sorry 'bout that. Thank you for your reply.
When I wrote ' back side of the 'A' port I meant the short side closest to the main exhaust window in a 3 port exhaust configuration. What I'm doing is installing a fresh air duct or tube into the ' A' port so that when there is short circuiting occurring there is plain oxygen instead of mixed fuel available in the right area of the 'A'port. No where can I find where, in the 'A' port, the right area is. Just so you know this air is reed valve regulated and it's atmospheric air but controlled by jet orifice. I've tried this on a KTM 85 and it seems to work good, but I'm sure it would work better if I new where to place the opening in the port.

wobbly

31st March 2023, 08:15

To be clear I regard the " front " of the cylinder is the Exhaust exit , except in the scenario of the cylinder turned around as a KZ is.
If I understand you correctly you are trying to achieve a version of stratified charge exiting the A port , but I really dont see how this can work effectively as the A port will begin flowing , instantly there is a positive pressure ratio across it.

Having a reed controlled auxiliary duct also into the same port , would take far too long to have flow to be initiated ,of air only.
Are you imagining that the initial A/F mixture is already on its way up the loop scavenging column , and then when maximum depression is seen at the Exhaust port around BDC , there is only air exiting the duct into the cylinder ?

Haufen

1st April 2023, 07:59

Hello again Wobbly
I think I have my front and back walls for the 'A' transfer port mixed up. Sorry 'bout that. Thank you for your reply.
When I wrote ' back side of the 'A' port I meant the short side closest to the main exhaust window in a 3 port exhaust configuration. What I'm doing is installing a fresh air duct or tube into the ' A' port so that when there is short circuiting occurring there is plain oxygen instead of mixed fuel available in the right area of the 'A'port. No where can I find where, in the 'A' port, the right area is. Just so you know this air is reed valve regulated and it's atmospheric air but controlled by jet orifice. I've tried this on a KTM 85 and it seems to work good, but I'm sure it would work better if I new where to place the opening in the port.

Stratified scavenging two-stroke engines went from reed controlled air ducts to piston controlled seperate air only inlets. The air in these inlets is then directed via closed pockets in the sides of the piston directly into the transfer outlet windows. The fuel / air mixture goes into the crankcase as usual and enters the transfers from there, whereas the air enters from the opposite side.

So the answer for your question with the reed controlled duct is: pretty close to the transfer exit (closer to the outlet than the transfer inlet at the case). But how close exactly would depend on the volume of the transfers you intend to fill, which would depend on rpm, load, mixing with air/fuel etc. As a ballpark, you could check if EngMod has a value for the scavenging efficiency (of the A ports only) and then dig through the numbers from there and see if you can come up with a compromise.

Or just convert the engine to fully stratified by adding a piston ported second inlet and get rid of the transfer-reeds:
the upper inlet is the air only inlet which feeds into the transfer outlet ends.

https://www.youtube.com/watch?v=3LDN0c2lAsQ

TZ350

1st April 2023, 09:07

jfn2

1st April 2023, 16:56

Hello Wobbly
Please understand the tube that's placed into the 'A' port is only .475mm in dia. So the amount of clean air is small. Also the reed cage is mounted as close to the port as possible. No more then an 1" to 1 1/2" (maybe 2") away. As the flow starts moving in the port towards the cyl and passes the mouth of the small tube it creates a low pressure over the tube and clean air moves into the port and into the cyl. It will flow more at low rpm's and less at high rpm's. This clean air is in front of the mixed fuel so therefore should be the first out of the exhaust port as short circuited mixture. So no mixed fuel is loss. I've found that I had to increase the low speed jet size about 1 size and sometimes move the needle clip depending on the size of the tube. Actually I have both connected with tubes into a metering block with one jet regulating the amount or air for both sides. So if I want more air I just increase the jet size. I did this to a KTM 85 some years ago for hill climbing and it worked good , but I did not have a dyno at the time so I have no feed back and I don't know where the bike is now or if it is still running. This should work well with also changing the 'A' port directional angle as Frits' mentioned. The only problem I can see is trying to use it with a parallel twin or triple motor.

Hello Haufen
Thank you for the reply. I assumed that was the place to locate it but I was not sure. What I'm still not sure of is how the short circuiting flow flows? The words short circuiting means, to me, is that as the flow comes out of the port it turns into the exhaust or does it travel around inside the bore mixing with the burnt' gases and then out the exhaust? Inquiring minds want to know!

Thoughts and comments.

Haufen

2nd April 2023, 00:16

Hello Wobbly
Hello Haufen
Thank you for the reply. I assumed that was the place to locate it but I was not sure. What I'm still not sure of is how the short circuiting flow flows? The words short circuiting means, to me, is that as the flow comes out of the port it turns into the exhaust or does it travel around inside the bore mixing with the burnt' gases and then out the exhaust? Inquiring minds want to know!

Thoughts and comments.

There are four basic loss principles:

1) loop scavenging losses: when the mixture goes all the way it is supposed to, but arrives at the exhaust port window while it is still open, so a portion of the mixture is lost. On a chainsaw etc. engine, this accounts for about 40% of the scavenging losses according to a publication from 2002 by STIHL.

2) mixing losses: when fresh and burnt mixture meet, a part of it will mix and join the exhaust gas route directly out of the exhaust port (instead of just pushing it out of the way).

3) wall losses: especially when fresh mixture hits the cylinder wall (e. g. because there is no ideal symmetry in the ports directions), that mixture can travel along the cylinder wall and out of the exhaust port

4) short circuiting losses: that's what happens when mixture, especially the mixture in the transfer ports which are closest to the exhaust port(s) takes a turn (short circuit) directly out of the exhaust port before even joining the scavenging loop.

TZ350

2nd April 2023, 07:51

2Stroke Stuffing.

<iframe width="560" height="315" src="https://www.youtube.com/embed/E6l2w-GVv34" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

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jfn2

3rd April 2023, 02:06

Haufen, again thank you for your reply .
I have a Kawasaki KX 65 I intend to play with as far as the short circuiting. I will try Frits' directional change first and then add the extra reed valves. I'll post the results. Thank you and Wobbly both for the help.

Peljhan

12th April 2023, 22:37

The combination of Mallory slugs and hollow light-alloy caps serves to combine a low total mass of the cranks with a high inertia that made the 250 cc twins more rideable. The same setup was used for the 125 singles, but as Jan Thiel said: 'In seven years of experimenting we have not been able to establish what is best: high or low inertia'.
My approach: when in doubt, choose low; it will be a blessing for the transmission and the rear tire.

Frits, I have a question about crank inertia.
I am wondering, shouldn't higher inertia crank be more blessing for transmission and rear tire as it's rotating speed oscilates less in each revolution?
Or is my theory applicable only when engine is more or less steady loaded and your statment refers to oscilations when gearbox is shifted?

P.S. It was nice to see you on video. :Punk:
Hope to meet you one day.

Frits Overmars

13th April 2023, 00:12

Frits, I have a question about crank inertia. I am wondering, shouldn't higher inertia crank be more blessing for transmission and rear tire as it's rotating speed oscilates less in each revolution? Or is my theory applicable only when engine is more or less steady loaded and your statment refers to oscilations when gearbox is shifted?
P.S. It was nice to see you on video. :Punk:Hope to meet you one day.Who knows?:D

As long as we are accelerating in one gear, a high crank inertia is indeed a blessing for the transmission and the rear tire because it will smoothen the torque spikes, caused by the combustion pressure.
The downside is that when shifting gears, the energy required to change the crankshaft rpm jerks the transmission and the tire. Especially downshifting, when the cankshaft is suddenly forced to rev much higher, can cause a heavy burden, corresponding to a multiple of the power produced by the engine.

By the way, some of you may remember the first outings of the Aprilia RSA125, which was sidelined by a broken inlet disk shaft a couple of times. The shaft calculation was based on the friction between the disk and the inlet cover, caused by the crankcase pressure, but the disk's inertia was neglected.
Jan Thiel warned that an 8 mm Ø shaft would not be strong enough, and he was proven right by one rider in particular with a 'heavy shifting down' foot.
There are some great pictures of the way the rider reacted. They are copyright-protected so I cannot show them. But in case you're curious...
https://www.google.com/search?newwindow=1&client=firefox-b-d&q=pasini+kicking&tbm=isch&source=univ&fir=crj63UGz76wneM%252CjxJs8-Chsz-xfM%252C_%253BNLajWZdNmtObcM%252CgqYnKSfVw8VAnM%25 2C_%253B1xU8jZHnwCK7XM%252CgqYnKSfVw8VAnM%252C_%25 3BMkCxyW0gcuydRM%252Cgc5Ch9oMHPgEvM%252C_%253BvO5G cA8VkV5l1M%252CjxJs8-Chsz-xfM%252C_%253B48RBPjUbAiWUxM%252CyCJwySbMR7HYlM%25 2C_%253B7UGoboSQQ3CDzM%252CgqYnKSfVw8VAnM%252C_%25 3B-7vqiHtnL3xEKM%252CjxJs8-Chsz-xfM%252C_%253BXPjhNO8wWBcL6M%252CBTLVKTgt73MGRM%25 2C_%253B6jw0D88V-oLqpM%252CjxJs8-Chsz-xfM%252C_&usg=AI4_-kRDcNUN85HVp6RSbOtyaUnx6E8COw&sa=X&ved=2ahUKEwj81J25t6T-AhXZuKQKHVAbA6oQjJkEegQIGRAC&biw=1175&bih=594

Peljhan

13th April 2023, 06:40

I remember this story from Jan, nice insight.

Wouldn't be a transmision disturbed more when upshifting with quickshifter as shift is allmost instantanious and when downshifting, clutch is usually used?
I wonder, maybe not, as crank need to drop revs only few hundreds when upshifting.

Maybe he should go play games, where only one ball is required instead of kicking poor Aprilia :facepalm:

Frits Overmars

13th April 2023, 09:38

Wouldn't be a transmision disturbed more when upshifting with quickshifter as shift is allmost instantanious and when downshifting, clutch is usually used? I wonder, maybe not, as crank need to drop revs only few hundreds when upshifting.Upshifting is usually done one gear at a time. Downshifting may be less friendly to the transmission, with some riders stomping on the pedal three times at once.
And clutches are for starting only, these days.

lodgernz

13th April 2023, 13:26

This would have been interesting. Alfa Romeo 2T V8 F1 engine prototype.
Looks like the intake is under the crankcase, so presumably used reeds.

352768

jamathi

13th April 2023, 17:15

Who knows?:D

As long as we are accelerating in one gear, a high crank inertia is indeed a blessing for the transmission and the rear tire because it will smoothen the torque spikes, caused by the combustion pressure.
The downside is that when shifting gears, the energy required to change the crankshaft rpm jerks the transmission and the tire. Especially downshifting, when the cankshaft is suddenly forced to rev much higher, can cause a heavy burden, corresponding to a multiple of the power produced by the engine.

By the way, some of you may remember the first outings of the Aprilia RSA125, which was sidelined by a broken inlet disk shaft a couple of times. The shaft calculation was based on the friction between the disk and the inlet cover, caused by the crankcase pressure, but the disk's inertia was neglected.
Jan Thiel warned that an 8 mm Ø shaft would not be strong enough, and he was proven right by one rider in particular with a 'heavy shifting down' foot.
There are some great pictures of the way the rider reacted. They are copyright-protected so I cannot show them. But in case you're curious...
https://www.google.com/search?newwindow=1&client=firefox-b-d&q=pasini+kicking&tbm=isch&source=univ&fir=crj63UGz76wneM%252CjxJs8-Chsz-xfM%252C_%253BNLajWZdNmtObcM%252CgqYnKSfVw8VAnM%25 2C_%253B1xU8jZHnwCK7XM%252CgqYnKSfVw8VAnM%252C_%25 3BMkCxyW0gcuydRM%252Cgc5Ch9oMHPgEvM%252C_%253BvO5G cA8VkV5l1M%252CjxJs8-Chsz-xfM%252C_%253B48RBPjUbAiWUxM%252CyCJwySbMR7HYlM%25 2C_%253B7UGoboSQQ3CDzM%252CgqYnKSfVw8VAnM%252C_%25 3B-7vqiHtnL3xEKM%252CjxJs8-Chsz-xfM%252C_%253BXPjhNO8wWBcL6M%252CBTLVKTgt73MGRM%25 2C_%253B6jw0D88V-oLqpM%252CjxJs8-Chsz-xfM%252C_&usg=AI4_-kRDcNUN85HVp6RSbOtyaUnx6E8COw&sa=X&ved=2ahUKEwj81J25t6T-AhXZuKQKHVAbA6oQjJkEegQIGRAC&biw=1175&bih=594

The inlet disc shaft was never calculated. I remember that I was hesitating between 10 and 12mm, then Gigi came by and decided on 8mm..... I was angry and went away! Later the problem was solved by putting a shock absorber in it.

Tim Ey

14th April 2023, 05:42

This would have been interesting. Alfa Romeo 2T V8 F1 engine prototype.
Looks like the intake is under the crankcase, so presumably used reeds.

352768

Isnt that the Mercury or Evinrude V8 of the Rudezon?
https://www.youtube.com/watch?v=RoiWpJLokEc

wobbly

14th April 2023, 10:10

Jan , were you too kind to tell Gigi he didnt know shit , and it should have been him who went away angry.
You were lucky the great leader didnt come by and tell you to use a chain drive - or something even dumber.

Seems like exactly the same torsional shock load that the first Cosworth DFV had with its cam drive . Duckworth fixed that with a super clever system of multiple tiny torsion bars with levers
inside one drive gear.

lodgernz

14th April 2023, 10:18

Isnt that the Mercury or Evinrude V8 of the Rudezon?
https://www.youtube.com/watch?v=RoiWpJLokEc

Certainly looks like it. I guess I was misinformed. Still awesome though.

husaberg

14th April 2023, 15:41

Jan , were you too kind to tell Gigi he didnt know shit , and it should have been him who went away angry.
You were lucky the great leader didnt come by and tell you to use a chain drive - or something even dumber.

Seems like exactly the same torsional shock load that the first Cosworth DFV had with its cam drive . Duckworth fixed that with a super clever system of multiple tiny torsion bars with levers
inside one drive gear.

He used a quill drive torsion bar on the Cosworth twin as well.
but that was an Norton mandated 360 twin no center bearing an a heap of other silly stuff. Like high mounted water pump etc

Muhr

15th April 2023, 05:01

Hey all!
Has anyone tried pushing the limits in terms of cylinder offset?
And if so, what kind of difference in character did you see.

wobbly

15th April 2023, 11:28

The issue with offset is that it makes the Exhaust especially , timing asymmetric.
Thus you may get a gain from it opening early , but then it closes later - that is where "going to some large limit " is heading.
Test like this at Vortex , just indicated that the opening timing was wrong in the first instance.

Frits Overmars

16th April 2023, 03:31

The issue with offset is that it makes the Exhaust especially , timing asymmetric.
Thus you may get a gain from it opening early , but then it closes laterOpening earlier and closing later did not sound asymmetric to me so I tried to do the math.
I chose values that are hopefully useful in practice: 54,5 mm stroke and 110 mm con rod length, first without offset and then with an offset of no less than 10% of the stroke: 5,45 mm. The engine may not like it, but my point is to make the effect of the offset crystal clear, and exaggeration can be enlightening

Whether the offset causes the exhaust to open earlier or later, depends on the direction of crankshaft rotation. I chose 'with' but you can mirror the values if you prefer.

Hopefully we are all familiar with the fact that any offset increases the distance between TDC and BDC (you may not believe me, in which case I have some more shocking news for you: the earth is not flat and not all politicians are honest).
More shocking news: the crank angle from TDC to BDC is larger than the crank angle from BDC to TDC (no, this does not mean that the piston will get lower and lower and drop out of the engine after some time). The net result is that neither TDC nor BDC are where you'd expect them to be in a zero-offset situation.

The only logical approach I could think of, is to use one and the same cylinder for the offset/no offset-comparison, and set the piston flush with TDC on both occasions.
I chose an exhaust timing of 196° which corresponds to a port top edge 26,82 mm below TDC, and a transfer timing of 130°, corresponding to 41,57 mm below TDC.

An offset version of the crank angle/piston position table ought to show all 360 crank positions because of the asymmetry (from TDC to BDC is not the same as from BDC to TDC) but I only show the part that is relevant to our port timing comparisons.

If you search for the crank angles corresponding to the 26,82 mm and 41,57 mm port positions, you'll notice that they deviate somewhat from the values in the zero-offset table, but not much.
If I didn't mess up the math, the exhaust opens 0,5° later and closes 1° later. Yes, it's asymmetric, but I wouldn't lose any sleep over it.

Muhr

16th April 2023, 06:09

I did something similar to see when something interesting happened..

Some examples of 4 strokes with offset

Suzuki does not offset its cranks. Honda has a 4.5mm offset. KTM and Husqvarna use 5mm of offset. Kawasaki has 8.5mm of offset, and the Yamaha YZ450F offset is 12mm(60,8 Stroke).

OopsClunkThud

16th April 2023, 06:50

did a quick mockup to see how the offset impacts the timing as it seemed like it could give more degrees for blowdown.

Ex: 190°
TR: 130°
offset 14.78mm (to give 185° on the down stroke, 175° on the up)

With zero offset there are 30° of blowdown
With 14.78mm offset there are 31.3° of blowdown

1.3° of extra blowdown with the same overall exhaust timing may not be much, but combined with the reduced side loads on the piston it seems like it could be useful configuration.

352775

Frits Overmars

16th April 2023, 10:44

14,78 mm offset in an engine with 51 mm stroke and a 97 mm conrod is a lot. You'll either need a real bigbore piston (not recommendable for a two-stroke) or you'll need to offset the cylinder. And yes, the difference in side load on the piston can be worth while.

ken seeber

16th April 2023, 16:49

D I R E C T C Y L I N D E R I N D U C T I O N (DCI)

So, after running the system (some time ago) with the DCI into the A ports, it was clear that there were no catastrophic backfires or explosions. However, the thing was compromised by the fact that the DCI was open to the cylinder during transfer opening period, but towards the TDC position the port communicated with the crankcase because of the piston skirt cutaway. So the poor old pressure waves inside the passages didn’t know what to and if they didn’t know, then I certainly didn’t.

Fortunately, the B ports were masked off by the piston skirt in the TDC zone, meaning the DCI passage only connected to the cylinder in the transfer open period (see pic). So, the B ports it is.

Lots of filling and cleaning up inside the passages to go, plus crankcase stuffer pieces as can be seen on the A port cylinder.

Might have it running in a couple of years.

352776352777352778352779

TZ350

16th April 2023, 17:39

JanBros

16th April 2023, 23:39

JanBros

17th April 2023, 06:44

CR1000

https://www.youtube.com/watch?v=1HzIABat-v8&t=1137s

senso

17th April 2023, 08:16

Thanks guys, i'll take a look.
This is what i'm working on: a 50cc Cagiva Prima racer.
This prototype reed valve is made to fit an Ibea 30mm carb on it, which has a 33,5mm exit diameter. It's a little bit large but i tried to arrange an acceptable internal duct.
This engine already has a nice inlet shape, and was born to also fit a 75cc so it has a 47mm large crankcase (bigger than a Minarelli or Derbi).
The cylinder base is with external studs so it's been possible to design a cylinder with proper transfer ducts.

Hi, this is most likely old news to you, but that cagiva engine seems pretty similar to the engine used in the Yamaha LCDE 50cc bikes, and if it is indeed an LCDE engine, then there are lots of parts for that engine, there is also a YZ80 big bore kit from Athena that also bolts on to the crankcase, and lots of long stroke cranks in Portugal for those engines.
You can also get a clutch basket from a DTR 125 and make it fit, or just turn the plate(most likely wrong name in english) and you can fit an extra clutch disk, DTR125cc metal clutch disks are around 0.5mm thicker, and thus give you a better cluch(a bit more clamping force, a little bit more wear resistance).

The 75cc version of that engine only lacked in the fact that the stock exhaust port was an oval, without much meat on the casting to do some exhaust aux ports..

Best regards, and sorry if I'm wrong.

Gradella23

17th April 2023, 19:29

Hi, this is most likely old news to you, but that cagiva engine seems pretty similar to the engine used in the Yamaha LCDE 50cc bikes, and if it is indeed an LCDE engine, then there are lots of parts for that engine, there is also a YZ80 big bore kit from Athena that also bolts on to the crankcase, and lots of long stroke cranks in Portugal for those engines.
You can also get a clutch basket from a DTR 125 and make it fit, or just turn the plate(most likely wrong name in english) and you can fit an extra clutch disk, DTR125cc metal clutch disks are around 0.5mm thicker, and thus give you a better cluch(a bit more clamping force, a little bit more wear resistance).

The 75cc version of that engine only lacked in the fact that the stock exhaust port was an oval, without much meat on the casting to do some exhaust aux ports..

Best regards, and sorry if I'm wrong.

hello senso,
i saw the yamaha lcde engine, it looks similar but it's not quite the same. Mine is a Cagiva made engine, and i don't think i can adapt much spare parts, except for maybe a derbi crankshaft (but it will need some lathe adjustments to fit on the clutch side.)
anyway i'll do everything by myself so problem solved!

the clutch from the 75cc version already has 5 discs so i think it will be enough.

TZ350

18th April 2023, 16:01

you can not dyno an engine with the variator opening in the powerband, as the speed of the dyno will rise but the rpm's of the engine do not. this means the final transmission-ratio is changing while dynoing and effects the powergraph. it is very difficult to read anything good out of the chart.

I do it with the variator blocked in a certain position that makes the dynorum long enough. so he should do just like that.
when the engine is setup properly, than I free the variator and adjust weights, clutch-springs etc so that I achieve the highest rpm of the dyno in the shortest amount of time, the ouput numbers don't mean shit at that moment, only the time matters.

solid line is the engine with blocked variator (about halfway), dashed line is after vario etc was properly setutp (don't read much in the numbers, it's a Honda Sky for moped-MX, max rpm about 9000-9500, HP I don't know, I only compare)

https://greentrade.international/Janbros/dyno.png

as you can see , the engine is suddenly capable a revving nearly 3.600 rpm higher, which of course is not possible. it's because the engine's rpm is calculated from the dyno's rpm.

We set our CVT engine up on a rolling road dyno (Dynojet) and graph power against road speed. This is a little four stroke engine in a sidecar for racing on Go Kart tracks. Springs, weights and rollers adjusted to get a flat power curve over the widest speed range possible.

352786

SwePatrick

18th April 2023, 23:12

Simple easy question:

What was the average weight of 250gp bikes during the latest years?

Rgds
Patrick

porttiming124

19th April 2023, 03:26

Hello everyone. Do you think it's better if the end of the stinger is sharp or with a radius?
If I look at the exit of the yamaha motocross silencer there is a lip just a bit before the exit.352787

Gradella23

19th April 2023, 05:14

hello guys, little update, almost ready to melt some aluminium....

katinas

19th April 2023, 08:12

Simple easy question:

What was the average weight of 250gp bikes during the latest years?

Rgds
Patrick

Hi, Patrick

From 2002 to 2009 weigh for 250 GP class, min. 100kg.
From 1992 to 2001 - 95 kg. and before 1992 - 90 kg.

Re Stinger or silencer exit

Hi, yes interesting question.
After reflected wave from revers cone travels backwards to the cylinder, the step at the end of the silencer restrict reverse flow from atmosphere and maybe this could delay returning time and weaken puls in comparison with rounded silencer end. But with a such small step, maybe no difference at all.
Say, the most restricted revers step could be a reed valve at the end of the silencer, without possibility for revers flow from atmosphere. It would be more clear comparison.

wobbly

19th April 2023, 09:52

Regarding the muffler exit geometry.
Now we have reliable code that can show the effects of the waves bouncing up and down the stinger , it became obvious to me that when the exiting wave front hits atmosphere it changes sign.
This negative pressure ratio then arrives back at the rear cone exit and can have a destructive interaction with the high pressure positive ratio being produced by the reducing cone area.

Thus the idea was tried ( initially being invented by Helmut Fath ) of a smaller diameter nozzle ,at the rear cone exit , that stepped up to the main stinger tube ID - where instead of having a smooth nozzle exit
into the main tube we had a step.
This step helped reduce the return waves amplitude and thus its effect on the main wave action within the pipe.

The dyno says yes please, and thankyou Neels.
I have never tried it but I will put a multi angle radius simulation on a stinger end and see what happens in EngMod.

porttiming124

19th April 2023, 10:34

ok thank you Woobly

skako

19th April 2023, 11:43

hello guys, little update, almost ready to melt some aluminium....

That looks great. Is the core made in the CO2 process? :niceone:

Gradella23

19th April 2023, 18:15

That looks great. Is the core made in the CO2 process? :niceone:

the core is sand 3d printed by voxeljet. I've built the outer core boxes with 3d printed plastic models screwed to the wood box

SwePatrick

20th April 2023, 18:32

Hi, Patrick

From 2002 to 2009 weigh for 250 GP class, min. 100kg.
From 1992 to 2001 - 95 kg. and before 1992 - 90 kg.

Nice!
Thank you.
I managed to get my Tz/Tzr project to 78kg so far.(no front fairing)
I have been obsessed this winter with trying to shave weight off of everything.
I´m aiming at 75kg´s(it´s becoming hard now)
Already bought every bolt and nut in titanium and aluminum
Exchanged all steel available on chassis to aluminum.
Lighter wheels and tires
Cut away unused brackets etc etc.

78kg´s is a success so far =)

katinas

22nd April 2023, 06:37

Nice!
Thank you.
I managed to get my Tz/Tzr project to 78kg so far.(no front fairing)
I have been obsessed this winter with trying to shave weight off of everything.
I´m aiming at 75kg´s(it´s becoming hard now)
Already bought every bolt and nut in titanium and aluminum
Exchanged all steel available on chassis to aluminum.
Lighter wheels and tires
Cut away unused brackets etc etc.

78kg´s is a success so far =)

78 kg weight with 250 cc two cylinder, impressive, it's completely on the edge.
With such a low weight, wheels/ tires/ brake discs, must be extra light, otherwise, softer springs in harmony with 78 kg will not be able to work with normal 250 wheels and tyres. Or if you leave the standard springs, the suspension will be very hard. The closest would be 125/moto3 wheels and tires.
Very light carbon brake discs can be made inexpensively from F1 brake discs from ebay (I bought few discs with pads for £50 per disc). After cutting one disc in half, you get two discs with a maximum thickness of 9 mm. Only needed to make the inner part of the brake disc from magnesium. Four lightweight carbon brake pads can be made from one F1 pad.

katinas

22nd April 2023, 06:45

https://www.ebay.co.uk/itm/374339219849

wobbly

25th April 2023, 13:38

After months of work on the factory Vortex KZ engine I have been tuning its all ready to run.
But , suddenly my SportsDevices SP1 Inertia dyno control box has a Coms issue and wont talk to the laptop.
Anyone on here using one , I only need it for a day to urgently to do a couple of runs , and can load my own dyno config file.
Any help very gratefully accepted.

husaberg

25th April 2023, 21:51

352947352948352949352950352951

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It took me a bit of looking to figure out they bead rolled the bracket to go over belly weld.

re the last pic knowing HRC i suggest the bracket might be hydroformed pressed rather than hand shaped.

SwePatrick

26th April 2023, 17:58

78 kg weight with 250 cc two cylinder, impressive, it's completely on the edge.
With such a low weight, wheels/ tires/ brake discs, must be extra light, otherwise, softer springs in harmony with 78 kg will not be able to work with normal 250 wheels and tyres. Or if you leave the standard springs, the suspension will be very hard. The closest would be 125/moto3 wheels and tires.
Very light carbon brake discs can be made inexpensively from F1 brake discs from ebay (I bought few discs with pads for £50 per disc). After cutting one disc in half, you get two discs with a maximum thickness of 9 mm. Only needed to make the inner part of the brake disc from magnesium. Four lightweight carbon brake pads can be made from one F1 pad.

Yes, i´ve been working hard.
Every little thing that i have bolted onto the bike needed to go through my lightening process, machine? lighter material? etc etc.
the handlebars for an example is carbon fibre, all fasteners thoughout the whole bike is either titanium or aliminium
All steel products exchenged for aluminium, i even have built my own rear shock.
the lower part of my upside down fork (dunno the word, normally the chromed steel tubes) are now aluminium.
Every little unused bracket is cut away on the frame and engine.
Engine has no kickstarter anymore, all gears to that are gone.
Front rim is an Magnesium 1.5" wide 17" rim.
Rear rim is an lightened frontrim from RGV250
Tires are lightweight ones, front is a tire that needs tube, but i run tubeless, rear is a PMT rain tire(soft rubber)
The fairing, (tankdummy and rear set) is one layer carbon fibre with some reinforcement on specified places.
But as i said, i doesn´t use a front fairing.
I even bought a new fueltank(1 litle) it´s weight is only 115g, the old one 1.2kg´s
The wheel axles and swingaxles are ofcourse titanium.
Made a new swing in aluminium.

And remember, it´s a 201m racebike, not a trackbike that is running lap after lap after lap.

Picture during process of making own rear shock:
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Grumph

26th April 2023, 19:19

Years back I had a 750 Kawasaki left in the shop after a visiting rider fell off and went home to heal. Looking it over it had titanium fasteners all over it and obviously a lot of money had been spent. When the rider returned a couple of weeks later i commented on the Ti bolts and showed him the equivalent size nylon fasteners. He'd never seen those and was surprised first at how light they were - and then by how cheap they were.
Absolutely fine to use for non - structural purposes.
John Britten went about it differently. Everything you'd expect to use 6mm fasteners used 5mm and there were similar size reductions all over the bike. If it had to be large OD, it was usually hollow.

More than one way to cut weight.

husaberg

26th April 2023, 19:42

Years back I had a 750 Kawasaki left in the shop after a visiting rider fell off and went home to heal. Looking it over it had titanium fasteners all over it and obviously a lot of money had been spent. When the rider returned a couple of weeks later i commented on the Ti bolts and showed him the equivalent size nylon fasteners. He'd never seen those and was surprised first at how light they were - and then by how cheap they were.
Absolutely fine to use for non - structural purposes.
John Britten went about it differently. Everything you'd expect to use 6mm fasteners used 5mm and there were similar size reductions all over the bike. If it had to be large OD, it was usually hollow.

More than one way to cut weight.

A modern 4t MX bike is a great example of fastener minimalization. if they went to the same efforts on the 2ts they would be 85-90KG's
One detail people often miss with the Britten was a aluminum front and rear hollow axles. It was a scaffold tube part about 1 7/8 inch 6061 series. 4.47mm thickness 48mm od
1.6KG/meter.
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To me Johns alloy axels rate higher than Poxy 12mm TZr250 and 15mm FZR axels.

Nowdays they even do front axels 22mm with "special bearing" on the YZ'fs and a few others.

69/22 2RS,
which is 22mm x 39mm x 9mm.
Rears, are 6905 2RS,
25mm x 42mm x 9mm

Kevin Cameron did a great one on the TR750 where the young engineers decided they could save some weight by adding dollars.
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edit
and no i am not saying that's what's going on in the posts above i utterly love the cf discs and engineered lightness

SwePatrick

26th April 2023, 20:11

This is a deep deep wormhole that one can make oneself not beeing able to get out of =)

husaberg

26th April 2023, 20:23

Sketchy's rear disk and Caliper is off a MTB
352961352962352963

SwePatrick

26th April 2023, 22:08

Sketchy's rear disk and Caliper is off a MTB
352961352962352963

Guess what i´ve got already? ;)
And also a bonus pic of new fork parts, not fully done yet, but as is ~600g lighter together witn the new 'shaft' that connects the both it´s over 1kg weight saving.

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husaberg

26th April 2023, 22:17

Guess what i´ve got already? ;)
And also a bonus pic of new fork parts, not fully done yet, but as is ~600g lighter together witn the new 'shaft' that connects the both it´s over 1kg weight saving.

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Now does that disk really need to be iron..... :laugh:
ktm50's have really neat calipers and master cylinders made by formula who made mtb brakes compete with plastic pistons and are nippleless.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTRwkXXPWJAT3_lJJlHynnUMDjwk3a1y oD3RA&usqp=CAU
for scale the disc is 140mm

pete376403

27th April 2023, 08:31

Kawasaki had plasma sprayed aluminium disks on their racebikes years ago. (pre carbon age) No idea how well they worked. Bro-in-law made an aluminium rear disk for one of Bruce Ansteys TZ250 as it only had to work for scrutineering, he never used the rear during races.

wobbly

27th April 2023, 10:13

Rotating mass ( angular inertia ) has a huge effect well beyond that of simply reducing the weight of everything in sight,
I have done a back to back with Mag wheels Vs BST carbons on a Superlight, the data showed the bike gained 6 bike lengths on the main straight at Hampton , and
then promptly broke the lap record.

And when testing the BSL500 V3 at Sepang we tried a 12,000 GBP carbon /carbon/Ti dry clutch assembly from AP.
When accelerating side by side out of the last left hander onto the main straight , the AP bike pulled a bike length on the standard one for each of the next 4 gear changes.
That was very cool , but it soon became obvious that none of the 3 people who tried could do a decent start , no matter what technique was used.
The thing either promptly stalled , or threw a huge wheelie . Nothing in between was possible. Luckily this could not break Mr Buckleys bank account or enthusiasm.

When we did a demo against the Britten at a race day we ran out of Carbon pads , so had to fit the front steels usually used in the wet.
It still did over 300Km/H but was 2 secs slower overall - still smoked Johns bike , with 155Hp and 115Kgs as you would expect.

Grumph

27th April 2023, 10:42

I've seen reports of hillclimb cars using the carbon/carbon clutches doing a clutch warmup by parking against a barrier and revving against a lightly loaded clutch.
Better feel apparently once hot. Still with little or no measurable wear after a season's use.
Bill B always appeared to have deep pockets but short arms at the pub when he came down here in his speedway sidecar days. That was a tough, hard drinking crowd of mad characters on the chairs.

F5 Dave

27th April 2023, 15:02

Kawasaki had plasma sprayed aluminium disks on their racebikes years ago. (pre carbon age) No idea how well they worked. Bro-in-law made an aluminium rear disk for one of Bruce Ansteys TZ250 as it only had to work for scrutineering, he never used the rear during races.

Ha, was going to use his bike as an example. Rear brake lever was made from Perspex.

Plenty of ally discs in Buckets. Use organic pads.

husaberg

27th April 2023, 17:21

Ha, was going to use his bike as an example. Rear brake lever was made from Perspex.

Plenty of ally discs in Buckets. Use organic pads.

for years the 50/80 and 125 gp bikes used alloy disc rotors Zanzani?
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Harry hunt sold ones in the states
The first i remember was the MV racers in the 70's
they were i believe plasma sparayed but you could i assume do one these days out of MMC

husaberg

27th April 2023, 17:22

Kawasaki had plasma sprayed aluminium disks on their racebikes years ago. (pre carbon age) No idea how well they worked. Bro-in-law made an aluminium rear disk for one of Bruce Ansteys TZ250 as it only had to work for scrutineering, he never used the rear during races.

Ha, was going to use his bike as an example. Rear brake lever was made from Perspex.

Plenty of ally discs in Buckets. Use organic pads.

for years the 50/80 and 125 gp bikes used alloy disc rotors Zanzani?
352966352967

Harry hunt sold ones in the states
The first i remember was the MV racers in the 70's
they were i believe plasma sprayed but you could i assume do one these days out of MMC

katinas

28th April 2023, 08:26

And remember, it´s a 201m racebike, not a trackbike that is running lap after lap after lap.

Yes, I forget that this is for drag race, so suspension less important than weight.
Another good option for rear could be the very light 16.5 front magnesium wheels. I use few 16.5 front wheels for rear, just made brake disc and sprocket adapter, whose shape allows little torsional movement (add photos).
A superb brake discs, could be made from car clutch flywheel disc. Stopping power of this special iron material is amazing. Disc can be made small in diameter and therefore much lighter while maintaining efficiency of bigger steel disc. One down side is rust.
Two other photos, rear ventilated iron disc made from Honda CBX 550 inner type brake adapted to CBR 600 lightened rear wheel 17x4.5. But material is not as good as from car clutch flywheel.

Some Honda NR/NS/NSR front forks tubes were made from carbon fiber with outside layer of thin chromed aluminium tube.

pete376403

28th April 2023, 09:19

A superb brake discs, could be made from car clutch flywheel disc. Stopping power of this special iron material is amazing. Disc can be made small in diameter and therefore much lighter while maintaining efficiency of bigger steel disc. One down side is rust..

A friend bought a write-off BMW K100 which required new discs. He had a couple made from LandRover flywheels - worked very well, although, as you say, always a light coat of rust in the morning - wiped off with the first application of brakes. (helped that he had access to a big lathe)

ken seeber

28th April 2023, 13:51

Wile we're on the topic of lightweight disc rotors, here's one that we do for karts:

https://www.kiwibiker.co.nz/forums/showthread.php/162399-The-Bucket-Foundry?p=1130999910&highlight=foundry#post1130999910

TZ350

28th April 2023, 15:29

.
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Blue line was the first cut Red line after some carb adjustments.

I had machined away the inside faces of the crank wheels as much as possible. I wanted to get as much crankcase volume as I could and with the wider space between the wheels I hoped it would reduce wind-age on the conrod as it passed between the cheeks of the flywheels. Also the big end oiling should be improved as it is completely un-shrouded now.

A lot of the counter balance had been machined away. No idea what the B/F was now or what it should be so I just tried it as is. The vibration is so bad at 9,000 rpm I had to throttle off. 9k was about 105 mph on the dyno. The aim is to be able to run on out to 10k which looks to be about 115mph.

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Ok. Re balancing the F81M 250 crank. Eight 14mm x 16mm slugs of Tungsten (99%).

Done one side, now have to swap over and do the other side. Looking for a 55% balance factor.

This engine vibrated real bad at 9,000 plus rpm. I am looking for a useful power spread from 7500, to 10,500 rpm. With the peak at 9,500.

The ignitions soft limiter is set at 10,500 and hard limiter at 11,000. But the limiter does nothing if the mixture goes leanish as then it runs away like a glow plug engine. On the occasions that it did this, I saw 12,000 plus before I could get my hand over the carb bell mouth and drown the engine into submission. Frightening.

TZ350

29th April 2023, 08:07

TZ350

1st May 2023, 15:57

.
352999

All this re balancing palaver started because I machined away the inside faces of the crank for better B/E oiling, less windage on the rod squeezing through the original narrow gap between the wheels and more crankcase volume.

353000

The original idea was to drill a size for size hole and hold the slug in with JB Weld. With the excess JB squishing out the 3,5mm pilot holes that were drilled right thru the crank cheek.

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52% balance factor was achieved with seven slugs of Tungsten. I had calculated 6,5 slugs but I guess on the finished job there was some air space behind the slugs.

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It turns out that the old drill cut slightly undersize so the slugs were a press fit and I did not need the J B Weld.

Seven slugs in total. Four one side three the other. I wonder if this will set up a rocking couple? And would it matter?

Vannik

1st May 2023, 19:11

A cautionary tale about crank balancing (I know it is 4T but still relevant):

https://www.youtube.com/watch?v=_RvNt8qWMgc&t=633s

F5 Dave

1st May 2023, 20:04

Lordy, I think I aged a month waiting for that dude getting to the point. First Tshirt adds, then talk talk talk.

Rob I think all this palaver actually started when you asked a mild trail bike engine to rev higher than its intended 4-6000 range. Unavoidable.

Looking forward to progress.

peewee

2nd May 2023, 03:15

CR1000

https://www.youtube.com/watch?v=1HzIABat-v8&t=1137s

excellent but why they dont put nitro in there .maybe scared ? :lol:

wobbly

2nd May 2023, 11:42

Rob - I have rebalanced many cranks with Mallory using a press fit - twice one slug has moved.
Its easy to TIG two small spots opposite each other , just fusion weld the two materials together , never had an issue since.

TZ350

3rd May 2023, 14:10

Rob - I have rebalanced many cranks with Mallory using a press fit - twice one slug has moved. Its easy to TIG two small spots opposite each other , just fusion weld the two materials together , never had an issue since.

Yes, off to Machine Parts Welding tomorrow, to stich weld the seven Tungsten slugs.

karter444

3rd May 2023, 19:47

Hi Wobbly,
Was wondering if you could answer a couple of questions , that may be of interest to others as well .

1. If you were running 100cc direct drive air cooled reed and rotary engines and your main concern was looking after the engine and extending engine life , what type of oil would you recommend ie either a castor based oil like castrol R or a fully synthetic and why .

2. Why is it that TM have designed the head and insert on the kz engine to have no coolant flow directly over the insert , I havnt seen this on other engines . I imagine the risk of deto would be reduced if the insert had direct water cooling . If the head and insert were machined to allow coolant flow over the insert would the jetting need to be adjusted leaner to achieve the same egt and if so are you just back to the same situation where you are still one jet away from deto to achieve max performance .

cheers Richard

Ocean1

4th May 2023, 08:57

Yes, off to Machine Parts Welding tomorrow, to stich weld the seven Tungsten slugs.

I'll be real interested to hear how that goes, even using a laser the melting temp difference is huge...

wobbly

4th May 2023, 10:08

TIG welding the Mallory to the wheel is easy , even Flet could do it without a microscope.

Re questions - the 100cc engines when you really lean ( yea jetting too ) on them always had issues locking up pistons.
But not bearings flying apart due to 20,000 rpm. Thus as long as you dont lean it down and are looking to extend life I would use a full synthetic like 800 simply due to the film strength.
Using Maxima 927 or Elf 909 which is what they would normally use ( R is bloody old hat now ) is only needed if it gets real hot.
In the Timken/Falex oil test machine a castor has bugger all film strength but has a lovely smooth wear pattern , a synthetic has well over 10 times the load capability , but the instant it is abused it breaks down into non lubricating
components.
Castor base , even when smoking up on the machine still lubricates the wear surfaces - the synthetic causes metal to tear off due to micro welding.

Re the TM head insert - I dont think this is covered by an NDA so here you are.
This idea makes more power - simple. The reason is that a hot combustion chamber surface has less temp delta with the burning combustion gas , thus conducts less of the finite fuel energy
away into the water. The squish band is closer to water thus stays cooler to help retard deto.
The only down side is the plug threads are hot as well , but in this case due to the straight line ignition we are deto limited in the squish , not limited by overheating the plug body and thus punching holes
in pistons due to pre ignition.
If you really wanted to get trick , put a clear ceramic on the combustion chamber surface only - ceramic is illegal , but hey you cant tech what you cant see.
I have tested super trick chambers that cooled the squish , and the plug , no dramatic advantage sadly.

Grumph

4th May 2023, 10:40

I remember Barry Lynch repairing KT100 cranks that had pitted on the surfaces rollers run on. He blamed the use of R for the pitting
R is hygroscopic - attracts and absorbs water.
He may well have been right too, I've seen similar pitting on things like Manx Norton cams - and a lot of those are still run on R.

Barry had quite a production line going at one time. Hard chroming and finish grinding KT100 cranks.

katinas

4th May 2023, 18:45

Re head

I still haven't tried a similar design, only instead of holes, the black head cover has a deflector that directs the flow down closer to squish band and then up towards the exit near the spark plug.

karter444

4th May 2023, 19:55

TIG welding the Mallory to the wheel is easy , even Flet could do it without a microscope.

Re questions - the 100cc engines when you really lean ( yea jetting too ) on them always had issues locking up pistons.
But not bearings flying apart due to 20,000 rpm. Thus as long as you dont lean it down and are looking to extend life I would use a full synthetic like 800 simply due to the film strength.
Using Maxima 927 or Elf 909 which is what they would normally use ( R is bloody old hat now ) is only needed if it gets real hot.
In the Timken/Falex oil test machine a castor has bugger all film strength but has a lovely smooth wear pattern , a synthetic has well over 10 times the load capability , but the instant it is abused it breaks down into non lubricating
components.
Castor base , even when smoking up on the machine still lubricates the wear surfaces - the synthetic causes metal to tear off due to micro welding.

Re the TM head insert - I dont think this is covered by an NDA so here you are.
This idea makes more power - simple. The reason is that a hot combustion chamber surface has less temp delta with the burning combustion gas , thus conducts less of the finite fuel energy
away into the water. The squish band is closer to water thus stays cooler to help retard deto.
The only down side is the plug threads are hot as well , but in this case due to the straight line ignition we are deto limited in the squish , not limited by overheating the plug body and thus punching holes
in pistons due to pre ignition.
If you really wanted to get trick , put a clear ceramic on the combustion chamber surface only - ceramic is illegal , but hey you cant tech what you cant see.
I have tested super trick chambers that cooled the squish , and the plug , no dramatic advantage sadly.

Hi Wob thanks for the reply .
re oil .Are you saying that under normal conditions a synthetic will have 10 x more load capabilities until it reaches a certain critical temp and then a castor based oil will out perform the synthetic .So if you stay away from that critical temp synthetic is the way to go .
cheers

speedpro

4th May 2023, 21:46

[QUOTE=Vannik;1131214764]A cautionary tale about crank balancing (I know it is 4T but still relevant):

That was one of the worst jobs I have ever seen, especially as SME is supposed to be a premium engine builder. The welding is crap, probably no weld prep, and I think I saw that it was only welded on one side.

wobbly

5th May 2023, 09:10

The fully synthetic oils became popular around the same time as the FIM mandated lead free race gas.
This fuel ( 100 octane ) made more power running slightly rich with more ignition and less com.
Thus the egt numbers were way below those when running 130 octane with 18:1.
This suited the synthetic stock perfectly , contrasted to most teams who earlier had various oil sponsors but all ran Castrol A 747 - a castor based product.
So yes , as long as the synthetic is not taken near its limit , it has far superior wear and lubricating properties.
The 10X film strength comment applied to using R30 - todays castor based oils are much , much better.

Edit - that SME video showing the idiot attempt at balancing the crank was doomed from the start. There is a rule of thumb we use in 2T that when fitting a bigger pin , or stroking you should
leave 1/2 the pin diameter of material in the wheel , above the hole. They didnt do that even close , and putting all the Mallory in one web , instead of splitting it across both for each cylinder pairs
was again plain dumb. SM I must say has manned up to fix it though , a very very expensive mistake.

Frits Overmars

5th May 2023, 22:26

That SME video showing the idiot attempt at balancing the crank was doomed from the start. There is a rule of thumb we use in 2T that when fitting a bigger pin , or stroking you should leave 1/2 the pin diameter of material in the wheel , above the hole. They didnt do that even close , and putting all the Mallory in one web , instead of splitting it across both for each cylinder pairs
was again plain dumb. SM I must say has manned up to fix it though , a very very expensive mistake.For mallory plugs, that do not require as much press fit as a big end pin, 1/4 x the plug diameter of material around the hole may be enough.

wobbly

6th May 2023, 08:44

Oh dear Frits , the memory retention is slipping , my appreciation for you still being clever.

pete376403

6th May 2023, 09:54

The fully synthetic oils became popular around the same time as the FIM mandated lead free race gas.
This fuel ( 100 octane ) made more power running slightly rich with more ignition and less com.
Thus the egt numbers were way below those when running 130 octane with 18:1.
This suited the synthetic stock perfectly , contrasted to most teams who earlier had various oil sponsors but all ran Castrol A 747 - a castor based product.
So yes , as long as the synthetic is not taken near its limit , it has far superior wear and lubricating properties.
The 10X film strength comment applied to using R30 - todays castor based oils are much , much better..

But does the exhaust smell as good?

TZ350

6th May 2023, 22:17

Gradella23

9th May 2023, 18:17

hello guys,
since there is limited literature around the web, i'd like to ask wobbly and all of you what your findings are about surface discharge plugs on 2 strokes.
The only sure thing i read online is that they need a steady and strong spark, but is this reachable in fact? Are there any comparison or bench test?

wobbly

9th May 2023, 18:25

Originally surface discharge plugs were used commercially in outboards when first CDI became available.
They needed a high discharge voltage as the effective spark gap was large from the center electrode out to the body.
Plug technology has advanced hugely since then with rare earth center and ground fine wire electrodes , that require less voltage than "ordinary " plugs and now we have no issues with fouling.
I can see no logic in using these nowdays in any specific application where they might be an advantage.

Grumph

9th May 2023, 19:23

Surface gap plugs were of course OE on the Kawasaki Mach 3. Which had I think one of the first CDI systems. Word at the time was that the higher discharge voltage eroded conventional plugs and shortened their service life. Surface gap plugs don't change the gap with age and use.

As Wob says, no reason to use them now. Technology has moved on.

husaberg

9th May 2023, 20:31

Surface gap plugs were of course OE on the Kawasaki Mach 3. Which had I think one of the first CDI systems. Word at the time was that the higher discharge voltage eroded conventional plugs and shortened their service life. Surface gap plugs don't change the gap with age and use.

As Wob says, no reason to use them now. Technology has moved on.

Weren't they spec'ed for the Mazda rotaries.

Flettner

9th May 2023, 20:35

This one runs a surface fire plug, out of a Rotary, 10 heat range, E85 fuel.

pete376403

9th May 2023, 21:04

This one runs a surface fire plug, out of a Rotary, 10 heat range, E85 fuel.
Surface gap plug was standard on my '72 F9, supposedly not as suceptible to fouling as a regular plug. It still did though.

Gradella23

9th May 2023, 22:10

Originally surface discharge plugs were used commercially in outboards when first CDI became available.
They needed a high discharge voltage as the effective spark gap was large from the center electrode out to the body.
Plug technology has advanced hugely since then with rare earth center and ground fine wire electrodes , that require less voltage than "ordinary " plugs and now we have no issues with fouling.
I can see no logic in using these nowdays in any specific application where they might be an advantage.

Surface gap plugs were of course OE on the Kawasaki Mach 3. Which had I think one of the first CDI systems. Word at the time was that the higher discharge voltage eroded conventional plugs and shortened their service life. Surface gap plugs don't change the gap with age and use.

As Wob says, no reason to use them now. Technology has moved on.

thanks.
so no advantage at all coming from the design itself, say a cleaner combustion chamber with no "shadow" from the electrode.

lohring

10th May 2023, 01:57

I had an idea to reform the combustion chamber of our 26 cc restricted engine class to lower the chamber volume. We were only allowed to remove material for modifications, but there were no restrictions on spark plug design. I suggested a plug with a large base that created a toroidal combustion chamber. My design used a surface discharge end. My friend, the late Jim Allen, liked the surface discharge idea and modified some conventional plugs. He was already running a toroidal head button in his unrestricted design 26 cc engine. I don't believe he found any advantage over conventional plugs in his toroidal chamber. Below are pictures of my idea and Jim's actual plug.

Lohring Miller

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wobbly

10th May 2023, 09:48

Regarding the spark gap " shadow " produced with a ground strap. I did dyno tests to prove or disprove the idea of indexing the plug , that rumour had it was an advantage.
In a box of 4 I by chance found two R 7376 -10.5 plugs that indexed 180* opposite each other.
One had the gap facing the Exhaust port the other facing the boost port.
The one with the unmasked gap facing the Exhaust I convinced myself after multiple back to backs was better , by maybe a 1/10 or 2/10 Hp - the width of the graph lines , probably not within the limits of the dyno read accuracy.
I still do it today , just because I did the test and it makes me feel clever , even though Frits has proved otherwise more than once.

skako

10th May 2023, 13:33

Here I slightly improved the previous version of the calculation for the suction flow into the crankcase of the 2T engine. The calculation is carried out according to the work of Dr. Hoffman. The calculation method is multiple iterative, conservative and preserves the flow of mass and energy through the orefice. I studying for further.

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Frits Overmars

10th May 2023, 20:07

Regarding the spark gap " shadow " produced with a ground strap...The one with the unmasked gap facing the Exhaust I convinced myself after multiple back to backs was better... I still do it today , just because I did the test and it makes me feel clever , even though Frits has proved otherwise more than once.That was never my intention mate. Anyway, two-strokes can make all of us look stupid.

philou

11th May 2023, 02:47

a French ignition manufacturer cuts or drill the ground electrode of its spark plugs.

it indicates that by testing the spark plug under pressure of 10 bars. the sparks go from the electrode to the base.

it indicates having a better revving without the ground electrode.

its ignitions are at fixed advance. according to him, the variable is useless. Turbulence velocity with rpm has the same effect

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skako

11th May 2023, 07:41

Here are some more interesting diagrams for analyzing waves and the charging effect. I was looking for the length of the suction pipe that gives the maximum filling of the crankcase. Everything else is unchanged. Crankcase temperature 358K, intake pipe temperature 280K, ambient temperature 293K, atmospheric pressure 1 bar.

353042353043353044353045353046353047

wobbly

11th May 2023, 17:30

Skako , I see a ref to the inlet as 118* what does this mean ie on your analysis where does the port open and close in relation to TDC .
Is that the pink line shown as IC around 59* before and after .

skako

11th May 2023, 17:48

Skako , I see a ref to the inlet as 118* what does this mean ie on your analysis where does the port open and close in relation to TDC .
Is that the pink line shown as IC around 59* before and after .

Yes, it's a pink line. It is a symmetrical intake. The intake port opens 59 degrees before TDC and closes 59 degrees after TDC. The total open time is thus 59° + 59° = 118°. This is the classic suction method for many older mopeds such as the Tomos.

353048

TZ350

12th May 2023, 13:00

I'll be real interested to hear how that goes, even using a laser the melting temp difference is huge...

353050

Ok. Welded Tungsten slugs.

The heat shrink on the rod was to protect the rod from being an accidental earth and causing a welding flash over and pitting of the bigend.

Next step, check the crank is still straight then re assembly.

husaberg

12th May 2023, 18:55

353050

Ok. Welded Tungsten slugs.

The heat shrink on the rod was to protect the rod from being an accidental earth and causing a welding flash over and pitting of the bigend.

Next step, check the crank is still straight then re assembly.

Does that have a speedy sleeve on the seal surface ?

TZ350

12th May 2023, 19:54

No speedy sleeve. This is the drive side. The drive gear has the seal surface for the rotary valve covers oil seal to run on.

RomeuPT

12th May 2023, 20:09

Hello again

Long time no posting.

I was having a conversation the other day with a friend and he came in conversation that low torque engines like bigger front sproket, this is not about the transmission ratio. He says that bigger cc bikes with high torque like smaller sproket, but low cc with high rpm big front sproket. He showed me a file where it talks about this, but its in Portuguese.

Then I research around some fast 125cc bikes and the sprokets tend to be from 17 to 20 so I got a bit curious about it.

Cheers

F5 Dave

12th May 2023, 20:54

Sounds like he is all torque.

TZ350

12th May 2023, 22:35

I was having a conversation the other day with a friend and he came in conversation that low torque engines like bigger front sproket, this is not about the transmission ratio. He says that bigger cc bikes with high torque like smaller sproket, but low cc with high rpm big front sproket. He showed me a file where it talks about this, but its in Portuguese.

Interesting. I would not have thought so, but I had not thought about it either.

If its true, we might need to look at how the choice of primary gear ratio which affects the torque loading stresses on the clutch has been chosen to see why a particular size front sprocket is needed. As I understand it. If a clutch is prone to slipping then reduce the primary ratio. This spins the clutch faster but reduces the potential torque multiplayer affect of the primary ratio.

A lower primary ratio would suggest a smaller front chain sprocket because the front sprocket would now be spinning faster too. But a high torque motor is usually one the reeves slower than a low cc high rpm low torque one. So the high torque engine would need a proportionally bigger front sprocket. I guess we need to look at the complete picture.

Out of interest, my 250 single road racer that is geared for 110 mph has a 17 front sprocket and a 38 rear 2,2:1. My TZ350 had 14 front and 34 rear 2,4:1. The TZ reeved harder and went faster. I will have to check the primary and top gear ratios to make any sense of it.

JanBros

13th May 2023, 07:47

does anyone have the arduino sketch for Adagnes's Ardyno ?
it's no longer available on his site. have mailed him butl no answer (allthough it's only 24h)

wobbly

13th May 2023, 08:28

I dont think you can discuss sprocket size in isolation , as in bigger, or smaller is better as a basic premis at all.
First you have the desired acceleration out of the slowest corner , offset by the top speed needed or more likely the amount of power available to generate that top speed.
But in a racebike the other aspect that is highly important is the chain run geometry that generates the squat characteristics out of every corner,
The smaller the front sprocket the greater the anti squat - if its needed.

Grumph

13th May 2023, 08:58

I agree with Wob. In addition it's complicated by Rob and I - and several others here - dealing with engines originally intended for dirt bikes.
They tend to have primary ratios chosen to give final drive sprockets that are a comfortable size at the lower gearing needed for off road work.
In the case of the Kawasaki's I remember Cameron when modifying his 350 single having trouble finding clearance for a larger front sprocket to suit the roadrace application.
It looks like my primary belt conversion is going to raise the gearbox speed appreciably - which will help with overall gearing.

pete376403

13th May 2023, 09:47

I agree with Wob. In addition it's complicated by Rob and I - and several others here - dealing with engines originally intended for dirt bikes.
They tend to have primary ratios chosen to give final drive sprockets that are a comfortable size at the lower gearing needed for off road work.
In the case of the Kawasaki's I remember Cameron when modifying his 350 single having trouble finding clearance for a larger front sprocket to suit the roadrace application.
It looks like my primary belt conversion is going to raise the gearbox speed appreciably - which will help with overall gearing.

IIRC in Camerons bike the original clutch actuator was a pushrod through the gearbox shaft operated by a bellcrank on the left side. He changed it to a pull operation through the clutch cover on the right side. Wonder what became of that bike?

lodgernz

13th May 2023, 10:33

does anyone have the arduino sketch for Adagnes's Ardyno ?
it's no longer available on his site. have mailed him butl no answer (allthough it's only 24h)

Do you mean the Simple Dyno sketch? I don't remember Alex offering a separate Arduino program.
Or do you mean the Ardyno circuit diagram?

JanBros

13th May 2023, 21:40

Do you mean the Simple Dyno sketch? I don't remember Alex offering a separate Arduino program.
Or do you mean the Ardyno circuit diagram?

the sketch that needs to be uploaded to the arduino. don't know if it's his own.

on this page : https://ardyno.weebly.com/instructions.html
under software, the second link "Download the Simpledyno zip file from here (https://sites.google.com/site/simpledyno/file-cabinet) and unpack it"

jfn2

14th May 2023, 02:09

Hello Jan
I have a copy of the simpledyno solfware zip file if that's what you need. I believe it's version 6.5.1
Jeff

JanBros

14th May 2023, 10:01

Hello Jan
I have a copy of the simpledyno solfware zip file if that's what you need. I believe it's version 6.5.1
Jeff

I have that too. so it's just the sketch that's whithin the simpledyno software that's alsovused with the ardyno ?

lodgernz

14th May 2023, 11:25

I have that too. so it's just the sketch that's whithin the simpledyno software that's alsovused with the ardyno ?

SimpleDyno provides the Arduino sketch that is is used to transfer the Ardyno signals to SD.
The Ardyno board is quite separate from SD and is just one of any number of input devices to SD, but SD requires the engine and roller data to be interpreted and sent to it via the SD sketch, always.

JanBros

14th May 2023, 23:32

SimpleDyno provides the Arduino sketch that is is used to transfer the Ardyno signals to SD.
The Ardyno board is quite separate from SD and is just one of any number of input devices to SD, but SD requires the engine and roller data to be interpreted and sent to it via the SD sketch, always.

ok, thanks

RomeuPT

15th May 2023, 03:21

I dont think you can discuss sprocket size in isolation , as in bigger, or smaller is better as a basic premis at all.
First you have the desired acceleration out of the slowest corner , offset by the top speed needed or more likely the amount of power available to generate that top speed.
But in a racebike the other aspect that is highly important is the chain run geometry that generates the squat characteristics out of every corner,
The smaller the front sprocket the greater the anti squat - if its needed.

Not sure if I understand what you mean.

Here is the file, but in portuguese.

It seems to be about how much dregress the chain bend per tooth with different sprokets.

353063

Frits Overmars

15th May 2023, 06:12

Here it is in Enlish. The only remark I can endorse is that gears with small numbers of teeth have drawbacks. But that is generally true; it has nothing to do with low or high torque.
In the old days (about a hundred years ago), when we had to design a machine, we got a beating if we dared to suggest gears with less than 20 teeth.
353064

TZ350

15th May 2023, 08:12

RomeuPT

15th May 2023, 11:39

Here it is in Enlish. The only remark I can endorse is that gears with small numbers of teeth have drawbacks. But that is generally true; it has nothing to do with low or high torque.
In the old days (about a hundred years ago), when we had to design a machine, we got a beating if we dared to suggest gears with less than 20 teeth.
353064

Thanks for the translation!

RomeuPT

15th May 2023, 11:42

Interesting. I would not have thought so, but I had not thought about it either.

If its true, we might need to look at how the choice of primary gear ratio which affects the torque loading stresses on the clutch has been chosen to see why a particular size front sprocket is needed. As I understand it. If a clutch is prone to slipping then reduce the primary ratio. This spins the clutch faster but reduces the potential torque multiplayer affect of the primary ratio.

A lower primary ratio would suggest a smaller front chain sprocket because the front sprocket would now be spinning faster too. But a high torque motor is usually one the reeves slower than a low cc high rpm low torque one. So the high torque engine would need a proportionally bigger front sprocket. I guess we need to look at the complete picture.

Out of interest, my 250 single road racer that is geared for 110 mph has a 17 front sprocket and a 38 rear 2,2:1. My TZ350 had 14 front and 34 rear 2,4:1. The TZ reeved harder and went faster. I will have to check the primary and top gear ratios to make any sense of it.

I guess if it was relevant no bike would come with less then a 20 sproket from factory but lets see what can be said here about it.

Grumph

15th May 2023, 14:18

I guess if it was relevant no bike would come with less then a 20 sproket from factory but lets see what can be said here about it.

Apples vs oranges. A gear with less than 20 teeth is weak as the gear cuts go too deep into the core material. They're stress raisers.
A sprocket can go down to around 12 teeth without losing strength as the bottom of the teeth are of appreciable radius thus much kinder to the
material used.

There are a lot of reasons for choosing a size for a final drive sprocket. You seldom see a big bike now with less than 18 teeth on the front sprocket - usually more.
Less angularity usually means longer chain life.

ken seeber

15th May 2023, 22:57

In Awestralia, the Yamaha KT100S engine was the mainstay of karting. Because they revved to around 15k rpm, they typically, in sprint/bitumen, used a 10T sprocket on the crank, driving an 85T or so axle sprocket, using a 219 chain.

However, these engines are very common in the increasingly popular dirt track karting scene. These tracks are usually shorter than bitumen tracks with lots of tight corners. Because of this, most use a 9T engine sprocket.

Not that I’m close to this. But I do know chain life is shorter, because of the dirt, the extra tension (11%) in the chain and the greater change of angle of each link over the sprocket (40deg vs 36deg).

RomeuPT

15th May 2023, 23:28

In Awestralia, the Yamaha KT100S engine was the mainstay of karting. Because they revved to around 15k rpm, they typically, in sprint/bitumen, used a 10T sprocket on the crank, driving an 85T or so axle sprocket, using a 219 chain.

However, these engines are very common in the increasingly popular dirt track karting scene. These tracks are usually shorter than bitumen tracks with lots of tight corners. Because of this, most use a 9T engine sprocket.

Not that I’m close to this. But I do know chain life is shorter, because of the dirt, the extra tension (11%) in the chain and the greater change of angle of each link over the sprocket (40deg vs 36deg).

I would say that if the chain is being eroded faster by too small sproket then a bit of the engine power is being consumed there instead of being spent on the road/dirt.

Most dirt bikes use 12/13/14 sprokets. Only for Aprilia or Honda RS its like 16 to 20....

This is probably known and tested...

Peljhan

16th May 2023, 00:22

Small sprockets also induce polygon effect. Smaller the sprocket, greater speed fluctuations in chain speed. One would think that this also put stress on chain and reduce it's life span.
353068

speedpro

16th May 2023, 21:09

Out of interest, my 250 single road racer that is geared for 110 mph has a 17 front sprocket and a 38 rear 2,2:1. My TZ350 had 14 front and 34 rear 2,4:1. The TZ reeved harder and went faster. I will have to check the primary and top gear ratios to make any sense of it.
Pukekohe gearing on my McIntosh was 15:27. I have a 16T I bought in the USA but haven't used it. The bike would pull it no problem, apart from me chickening out.

TZ350

20th May 2023, 09:49

husaberg

21st May 2023, 23:16

https://www.youtube.com/watch?v=pgGz00VTKgQ

https://www.youtube.com/watch?v=veCXLdDnFu0

diesel pig

22nd May 2023, 14:33

Watching that Pro-Am race one part of me was like those crazy young lunatic's with no fear and another part of me was I wish I was young again.

Peljhan

23rd May 2023, 10:32

I am bulding low power Puch E50 engine with 70cc kit. Will make about 5-7hp. Exhaust will be very long and I am wondering what kind of effect would have a reverse cone modification, if I would cut it in half in the middle and turned last part around so the spike would protrude towards mid section. Stinger pipe would again revese towards outside and this reverse cone would make nice place for silencer packing.
Does this modification shortens returning pulse and makes it of higher amplitude?
Should I than make the reverse cone with more shallow angle?

I believe Frits or Vannik would have some idea about theroretical effect of this modification.

Made quick sketch in paint. (blue color is silencer packing).
353158

P.S. Frits, what program are you using for sketches, they come out quite nice?

Edit: spelling

Frits Overmars

23rd May 2023, 12:22

Cutting the reverse cone in half and turning the last part around as in your above drawing would be like making a reverse cone with half the length and twice the steepness of the original reverse cone. It would be the oppositie of what you need for your low power Puch.
I know length can be a problem. Maybe you can make a curled header, like in the prictures below.
Thank you for your comment about my sketches. Some of those are generated by the software I wrote, some are made with Autocad, and some are produced with Microsoft Paint, so nothing fancy.
353161 353160 353159

wobbly

23rd May 2023, 15:20

The backwards cone idea doesnt work , been there done that 30 years ago . Easy solution is to go with the simple direct drive kart pipe with the rear cone full of small holes and enclosed within the tube body.
Neels has even got this modelled already - works really well for low power over a wide range.
I used this on a 2 cylinder fan cooled micro aircraft engine years ago , the pilot loved it - got up on the prop way faster and had a ton more overev power that gave alot more flight speed.

Peljhan

24th May 2023, 00:34

Thanks.

The problem is Frits, I dont know where to curve it anymore. I tried aiming it towards floor but forks are in the way. I try to keep it tidy.

A bit of insight. Our general medical insurance does not provide electric attachment (like Batec) to young paraplegics, their agument is funding and that we have healthy hands. I live in 500m deep walley full of mountain roads.
And this attachemnt cost about 6-8000eur :no: It is also underpowered with just 1200W electric engine.

So I decided to do it my way. Found a Puch E50 in the attic and after weeks of abusing Solidworks (or Solidworks abusing me) and some reverse engineering from my friends Batec, I came up with that. :Punk:
It is also a nice tribute to two strokes and laugh against electrification.

Wobbly, do i need to make enclosure for perforated rear cone like straight pipe with cap, or full cone few cm behind perforated cone?
Frits, I am using paint for simple sketches but it's not good for more precise or detailed sketches.

353162353163353164353165353166

Frits Overmars

24th May 2023, 02:38

The problem is Frits, I dont know where to curve it anymore. I tried aiming it towards floor but forks are in the way. I try to keep it tidy.I'm sure you've put more thought into it than I have, so maybe I'm missing something, but I do see potential in the header. A big part of it appears to be straight in your drawings. For the engine power you are aiming for, that header does not necessarily have to be conical; it may also consist of parallel piping. And 90°-elbows are available for many diameters, for example from companies that build four-stroke exhaust systems. You can build a knot using such elbows, so to speak, without much welding being required.353169

One more note, the power train on your Flying Puchman looks rather similar to another front-wheel drive two-stroke I've dabbled in: the Solex.
I have noticed that for light operation and sufficient feedback you have to keep the polar inertia around the steering axis as low as possible.
So build the engine as close to the steering head as you can.
353167

Grumph

24th May 2023, 07:14

For looped headers, donuts are a good starting place. Available from 4T exhaust bend suppliers in a range of OD's and sometimes radii.
Cut and twist.

Peljhan

24th May 2023, 08:02

I build many complete pipes with hydroforming. But I just finished excel driven sheet for Solidworks and decided to make it that way. It will be faster as cnc laser company is close and I weld it up in a day or two and I never tried hydroforming on stainless. Additionally I have to send it to laser cut anyway as my forks and frame is welded up from sheet metal.

Local company that builds 4t pipes is Akrapovič :D
But they got only large diameters available, like 40mm+
Stainles steel stores have mostly 1,5mm wall thickness and nothing on stock.

I attach pipe dimensions. For now header is 0,7/1,4°. Cone angles are half angles as I am used to that. And rear cone is one piece.
Made to run 167°-170° of exhaust timing and around 6700rpm peak power. 128° transfer timing. Will se how that will fit as I never made so low rpm tuned engine. And rpm needs to be low as it will be used onl up to 30km/h. I have better ways to die.
Cylinder is dmp70, 4 transfers with rear side 2 booster transfers.

353171

Would put it into EngMod but I want to drive around over the summer, so no time for that for now.

Polar inertia = moment of inertia around steering axis?
I made forks as you can se in a way that axle is a bit more forward and steering axis is quite inclined, so it tends to keep the direction of riding = harder to steer. But because mass is high I believed it will easen on turning the steering bar. We will see :D

Haufen

24th May 2023, 09:12

I dont know where to curve it anymore. I tried aiming it towards floor but forks are in the way. I try to keep it tidy.

If space and pipe length are an issue, looking into other types of exhaust pipes might also be an option, e.g. box type, perforated rear cone ones, a shorter pipe with an ATAC and so on.

wobbly

24th May 2023, 09:39

Any header down at 1.4* included will achieve nothing. Never has , never will , double it.
Why do weird , when weird doesnt work.
An enclosed perforated rear cone would work well in this application , but the " muffler " tube would end up longer than a normal pipe end point - less the stinger.
But an internal stinger would help anyway.

Peljhan

24th May 2023, 10:24

I don't want to go over 80mm on belly section because of size. 2,8° header would end with 43,6mm diameter. Wouldn't that weaken the difusor acting as it would need to be shallower to get length back?
These engines are old school design (small crankcase volume). Is in this case difusor action less expressed as it is can't pull from crankcase that much as modern design?

If I make perforated cone with enclosed chamber, I will put a hole in side of enclosure and make standalone muffler facing back. Or similar as on attached picture.

Wobbly, is that a design I should use? Should total exhaust length be changed or it should be same as with full (classic) cone?
I used a picture from Frits files.

353173

wobbly

24th May 2023, 10:52

The header angle increase would have more beneficial effect than any down side from a shallow diffuser. Make the diffuser 2 cones , 2/3 - 1/3 lengths.
You are dealing with no bmep here.
The vevey was originally designed for an engine pulling more than twice your design rpm , an adaption of this would need to be twice as long.
So as I said the muffler tube ends up being longer than your " ordinary " pipe design.
And the later designs that I did of this type of pipe ended up with a 3* tapered header as well.

Peljhan

24th May 2023, 11:45

I had the rear cone and muffler design in mind from Vevey picture, not complete dimensions.
Will make a change. Anyway I must build it for this summer riding and make some development over winter.

If I understood, the perforated angle cone with enclosure should have smaller angle than same classic style cone?

wobbly

24th May 2023, 13:29

Well its going to be shallower by making the body only 80 Diameter anyway.

philou

24th May 2023, 20:17

how long should the lobe flywheel be for an ignitech?

does its length have a function? capacitor charging time or other ?

353174

Peljhan

24th May 2023, 23:21

how long should the lobe flywheel be for an ignitech?

does its length have a function? capacitor charging time or other ?

353174

I can tell you info only for Zeeltronic. It should be min 2mm height difference and about 25° of "length".
If you get spark at the end of step, but you want it at beginning, you need to interchange pickup wires. Signal is listening when step happens.

wobbly

25th May 2023, 08:09

The Ignitech lobe height works at anything from 1.5 , but length can be anything from about 8mm to 25mm.
I have split a 24mm lobe into 2 with an 8mm gap to enable twin fire on a 180* twin that originally ran wasted spark.
The ECU spits the dummy if the lobe is over about 25mm , it does have a " long lobe " option but I simply shortened a longer 50mm Chinese flywheel lobe in the mill due to misfiring.
It also differs in that its recommended you use the falling edge to fire, as this is a specific characteristic of lobe triggering - whereas noise can trigger the ECU with rising voltage spikes.
This is the default situation that occurs when the base timing is set with the falling edge past the trigger pole , with the piston at TDC.

EDIT - you must use a resistor plug and cap , and note that the trigger input and the coil output are on opposite ends of the connector.
Keep all other wires well away from the coil outputs - this is the biggest cause of misfire issues people have by insisting on bundling everything together in a " loom ".

diesel pig

25th May 2023, 18:28

Keep all other wires well away from the coil outputs - this is the biggest cause of misfire issues people have by insisting on bundling everything together in a " loom ".

Just to be clear the pick up coil(or coils) wires should be keep separate from all other wires from the pick up coil until they go into the CDI ? and if it is a multiple coil set up should the wires for each coil be keep separate from each other?

wobbly

26th May 2023, 08:53

In a word yes , the input trigger wires should be routed well away from the coil wires. I always have the trigger (s) on one side of the bike , the coil wires (s) on the other.
These are on opposite ends of the ECU connector for a reason.
And the grounds for the trigger inputs , and the power grounds , are separate as well , and should also be physically routed apart.
The white and orange coil drive wires can be side by side and this has no effect on the triggering accuracy.
But be aware though , the output wires ( such as a PV drive or PJ switching ) if routed in a loom with the trigger inputs will generate errors and misfires due to EMI crosstalk.

diesel pig

26th May 2023, 12:52

In a word yes , the input trigger wires should be routed well away from the coil wires. I always have the trigger (s) on one side of the bike , the coil wires (s) on the other.
These are on opposite ends of the ECU connector for a reason.
And the grounds for the trigger inputs , and the power grounds , are separate as well , and should also be physically routed apart.
The white and orange coil drive wires can be side by side and this has no effect on the triggering accuracy.
But be aware though , the output wires ( such as a PV drive or PJ switching ) if routed in a loom with the trigger inputs will generate errors and misfires due to EMI crosstalk.

Interesting stuff, I will be going over my wiring looms very carefully to make shore I have not done something bad by mistake.

wobbly

26th May 2023, 15:43

Its not really doing something bad by mistake , the real issue is Ignitech and others dont tell you this basic stuff , that more often than not prevents anything approaching a " plug and play " scenario.
The only solution is to spend years of tracking down the issues others have unknowingly created , and going grey and or bald in the process.
I really wish I had someone telling me how not to fuck it up 20 years ago.

TZ350

26th May 2023, 17:40

.
353179 353181 353182

The re balanced crank works a treat. Reeves to 10k now no problems. Smooth as. Now for a bit of serious tuning on the dyno.

F5 Dave

26th May 2023, 20:47

Have you polished the crank seals and the Primary drive nut?

TZ350

27th May 2023, 10:13

TZ350

29th May 2023, 21:43

353193

Making progress, a solid 40rwhp from a 1970's 250 single.

Trying to setup the carburetor jetting from scratch is challenging. Without any petrol base line to work from it is all trial and error finding the right ignition and jet combo for methanol.

I re checked the Ignitec and trigger setup. Now the ignition timing graph is much more sensible and in line with what some other people with methanol experience have told me to expect.

But the engine has been running on at the end of a dyno pull. It just wont shut off but keeps running on. It seems to be glow plugging on NGK BR10EG's.

Enriching up results in more sever running on. I guess the richer it is, the colder it is and less of the fuel is evaporating which results in the mixture going leaner. The plug or its earth strap could also be running too hot.

More work tomorrow, slowly reducing the main jet and maybe adding a dash of Acetone to help ward of Methanol's tendency to auto ignition.

Frits Overmars

29th May 2023, 22:43

... the engine has been running on at the end of a dyno pull. It just wont shut off but keeps running on. It seems to be glow plugging on NGK BR10EG's.
Enriching up results in more sever running on. I guess the richer it is, the colder it is and less of the fuel is evaporating which results in the mixture going leaner. The plug or its earth strap could also be running too hot.Enriching resulting in going leaner does not sound very likely to me. Neither does glowplugging on NGK 10-plugs, although I cannot exclude it.
Bringing coolant close to the plug threads has solved some problems in the Aprilia racing engines. Increasing the coolant circulation speed and lowering its temperature should help. And you might try a surface discharge plug; that would definitely exclude glowplugging.

But I rather suspect you are experiencing HCCI: Homogeneous Charge Compression Ignition. Lowering the compression ratio (how high is it now?) could give a clue. It may decrease engine power but increase your knowledge.
One way of inducing HCCI is pre-heating the combustible mixture using EGR, which normally stands for Exhaust Gas Recirculation, but in two-strokes comes down to Exhaus Gas Retention. From a certain rpm onward the blowdown time.area becomes insufficient and exhaust gas that has not had the time to leave the premises heats up the fresh mixture. Too small an end cone restrictor or silencer could be a culprit as well.
If you are willing to sacrifice a piston, you can file 1 mm off the edge that controls the exhaust timing while avoiding to touch the parts of the edge that control the transfer timing. This will increase the blowdown angle.area sufficiently to give an indication whether that was the problem.

Vannik

29th May 2023, 23:32

Enriching up results in more sever running on. I guess the richer it is, the colder it is and less of the fuel is evaporating which results in the mixture going leaner.

This usually means the float bowl runs empty sooner. How sure are you that you have a big enough feed to the bowl?

Frits Overmars

30th May 2023, 01:48

This usually means the float bowl runs empty sooner. How sure are you that you have a big enough feed to the bowl? Didn't think of that. Makes sense; thank you Neels.
Now that you remind me, restricting the flow to the float bowl used to be a trick in the 100cc direct-drive kart era to automatically lean the mixture when running WOT on the straight, to wring some extra revs out of the engine. Quite risky....

wobbly

30th May 2023, 09:06

Frits , TeeZee's thing is aircooled , that is the real reason for the jungle juice.
I found years ago that when really pushing an aircooled and using rich mixtures to keep the cylinder cool , an 11 plug was needed.
Never thought of a surface discharge - would probably work well with dual Ignitech CDI into the Crane coil.
Also had the issue Neels came up with , the only way to keep the bowl full was to use a 4.5mm Dellorto methanol specific float valve.
And yes Frits , the drivers back then were well versed in running very lean at WOT then semi choking the carb for the last 1/3 of the straights.

Grumph

30th May 2023, 10:54

Frits , TeeZee's thing is aircooled , that is the real reason for the jungle juice.
I found years ago that when really pushing an aircooled and using rich mixtures to keep the cylinder cool , an 11 plug was needed.
Never thought of a surface discharge - would probably work well with dual Ignitech CDI into the Crane coil.
Also had the issue Neels came up with , the only way to keep the bowl full was to use a 4.5mm Dellorto methanol specific float valve.
And yes Frits , the drivers back then were well versed in running very lean at WOT then semi choking the carb for the last 1/3 of the straights.

Those were the days when you could pick out a top 100 driver in the bar by the short fingers...

TZ350

30th May 2023, 13:57

I rather suspect you are experiencing HCCI: Homogeneous Charge Compression Ignition. Lowering the compression ratio (how high is it now?) could give a clue. It may decrease engine power but increase your knowledge.
One way of inducing HCCI is pre-heating the combustible mixture using EGR, which normally stands for Exhaust Gas Recirculation, but in two-strokes comes down to Exhaus Gas Retention. From a certain rpm onward the blowdown time.area becomes insufficient and exhaust gas that has not had the time to leave the premises heats up the fresh mixture. Too small an end cone restrictor or silencer could be a culprit as well.

HCCI sounds possible. Single Ex opens 80 deg ATDC and is 72% wide. Not keen on going any more than that. Maybe time for that triple exhaust port modification I have in mind. A very cunning plan. The end cone restrictor is 32mm sure looks big enough but I will re visit that.

From memory, the compression ratio is 14:1 swept on a 70mm bore, 45% squish at 0.9mm clearance.

TZ350

30th May 2023, 14:05

Enriching up results in more sever running on. I guess the richer it is, the colder it is and less of the fuel is evaporating which results in the mixture going leaner. The plug or its earth strap could also be running too hot.
This usually means the float bowl runs empty sooner. How sure are you that you have a big enough feed to the bowl?

That sounds very likely, Thanks.

Also had the issue Neels came up with , the only way to keep the bowl full was to use a 4.5mm Dellorto methanol specific float valve.

Cant manage 4.5mm but was able to drill a standard Mikuni out to 3.5 and modify it for improved flow through the valve itself (hopefully).

353195 353196

pete376403

30th May 2023, 15:33

That sound very likely, Thanks.

Cant manage 4.5mm but was able to drill a standard Mikuni out to 3.5 and modify it for improved flow through the valve itself (hopefully).

353195 353196

The float valve holder in the 38mm Mikuni round slide carb on my jawa speedway bike had a horizontal cut (1 - 1.5mm wide) just below where the float valve seated. Allowed the fuel (Methanol) straight into the bowl as soon as the valve was of its seat, rather than having to get past the sides of the valve.

Grumph

30th May 2023, 15:46

Mk1 Amal concentric alcohol float bowls have the same thing - a slot just up from the needle seat about 2mm deep and around 1/3 of the circumference of the needle housing. They also have large 3 sided float needles running in a bore about 9mm ID, Actual bore of the orifice is probably 4mm.

If all else fails you could always pressure feed the carb. It violates KISS - but if it works...

wobbly

30th May 2023, 18:24

3.5mm is too small even if its modified , and I never could get drilled seats to seal.
The Dellorto seat is the same sort of shape - you can modify the carb body to use that.

husaberg

30th May 2023, 20:15

Pretty sure Neil made a lake injector they had no float bowl. pre 1970 so legit for class
353197353199353200353201
or here is an aussuie moded concentric on an alcohol hardlet classic racer with a concentric amal with a flat bowl off a strongberg carb from a valiant.
353198

the other mod that might help
https://thunderproducts.com/product/mikuni-float-bowl-extender/
https://thunderproducts.com/wp-content/uploads/2019/04/Float-Bowl-Spacer.jpg

Also make sure your needle jet is big enough as per one of the first posts in the tread:msn-wink:

.

This is Thomas a Vietnamese race mechanic, you know that place where they have all those hot 50's and 125's are big bikes.

Thomas, ESE's Race Team's Tuner is fettling number 9. adjusting the port timing for Taupo.

Its hard to see but he has taped a degree wheel to the magneto flywheel so he can mark out the exhaust port height he wants.

None of this raise the port 3.5mm for a gazillion HP nonsense. He knows what timing he needs and sets the crank position there before marking the port and then doing the hells death port job that we all dream of.

You should see him setting up a carb. Talk about pain staking, he starts with a main jet so big the bike floods at about half throttle (apparently this proves the oriface of the needle/needle jet combo is big enough) and then he slowly step by step works back until it runs clean.

Most people start at the bottom with a carb and work up, He starts at the top and works backwards.

Never seen him blow one up. But then he is intelligent with the throttle and does not ring its neck when the engine is in distress.

Boy o Boy am I Looking forward to Taupo.

.

Flettner

30th May 2023, 20:36

At the two minute seventeen second mark, 350 Bighorn with Lake Injector, E85. The only day I got it to run nice, won its class. I still have the Lake Injector under the bench somewhere. I moved on to electronic injection after this, all hidden inside, no one knew.
https://youtu.be/7CSXHo3jLVc

husaberg

30th May 2023, 20:45

At the two minute seventeen second mark, 350 Bighorn with Lake Injector, E85. The only day I got it to run nice, won its class. I still have it under the bench somewhere.
https://youtu.be/7CSXHo3jLVc

you re a little short of travel on that was it dt360? frame.
the dude on the cr125 at 355 or so must have massive nuts.

F5 Dave

30th May 2023, 21:12

Brass is a swine to drill you are supposed to modify bits to do it properly.

I've done it before with normal bits with 50% success, but not that big.

I drop a ball bearing in hole and give it a smart tap to make seat best it can.

I've also cross drilled the carb body. Drill out the ball bearing and see how small the cross drilling is. 24mm mikuni flat needed this, maybe meth needs on bigger ones?

Flettner

30th May 2023, 21:15

you re a little short of travel on that was it dt360? frame.
the dude on the cr125 at 355 or so must have massive nuts.

I think so, I dont remember when it changed. Its been DT frame for a long time now, way better than the shit old Kawasaki one.

pete376403

30th May 2023, 21:53

One of the speedway bikes i raced against had a Wal Phillips fuel injector, very similar to the Lake. Philiips was an old racer from way back in UK
https://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=55864&Searchpage=4&Main=7214&Words=WAL+PHILLIPS&Search=tru

Frits Overmars

31st May 2023, 01:26

Restricting the flow to the float bowl used to be a trick in the 100cc direct-drive kart era to automatically lean the mixture when running WOT on the straight, to wring some extra revs out of the engine. Quite risky....

Yes Frits the drivers back then were well versed in running very lean at WOT then semi choking the carb for the last 1/3 of the straights.

Those were the days when you could pick out a top 100 driver in the bar by the short fingers...The innocent young readers among us may feel the need for some further explanation regarding those short fingers.
Putting a hand over the carb bellmouth can be a risky business on a rotary inlet disk engine with an open chain drive directly from the crankshaft to the rear axle.
I've seen riders taking their right glove off after the race with a finger tip still in it.

Wob, running lean at WOT and semi choking the carb for the last 1/3 of the straights was indeed semi-common practice but it never made much sense to me.
What you needed with those direct drive engines, was a clean pull out of the corners, so you would fit the shortest gearing that would not cause too much loss of time on the last part of the straight where the engine would run out of revs. Running lean all the time and putting a hand over the carb at the last part of the straight would seem counterproductive.

On the other hand (pun intended) putting that hand over the carb when you went off the throttle could be an engine saver. But I was rather careful with my riders' fingers so I gave them an ignition cut-off switch coupled to the brake pedal. That way they could keep both hands on the steering wheel at all times, driving WOT even while braking, providing the engine with lubrication and internal cooling.

Now for the trick with the restricted flow to the float bowl. Driving WOT would cause a gradual drop in float bowl fuel level and an accompanying leaning of the mixture.
In the twisty parts of the track WOT would never take more than two seconds, but on the straight it would start making a difference.
Like I said, it was a risky bussiness, and putting a hand over the carb would not do much good if the fuel level in the bowl was too low.

the other mod that might help
https://thunderproducts.com/product/mikuni-float-bowl-extender/What good would an extra volume of fuel do if it is too low in the bowl?

Grumph

31st May 2023, 08:10

What good would an extra volume of fuel do if it is too low in the bowl?

I've had to deal with fuel surge in the course of working with sidecars. If there's a central nut on the float bowl, an extension to deepen the area the mainjet picks up from - and an extended mainjet to match - works just fine.

I'd assume an extended mainjet would work satisfactorily with that deepened float bowl. It would at least extend the time before running out of supply.

I also agree with Dave above. Look at the fuel passages from hose to top of float needle. If necessary, drill out the unused side and feed from two taps to both sides of the carb.

wobbly

31st May 2023, 09:06

Just as it was back in the 100cc days the top peddlers now use the hand choke idea in KZ.
The jetting can be set on the dangerous side of safety and this boost of leaness can be optionally used to make a pass or catch a competitor.
When its not needed during the race a hand in front of one of the airbox inlets drops the egt by 30*C, safe as.
Really good guys know exactly how much they can get away with , and realize you dont have to take the piston home after tech.

pete376403

31st May 2023, 09:30

Brass is a swine to drill you are supposed to modify bits to do it properly.

grind back the rake on the cutting edges to almost nothing, (as told to me during my apprenticeship)

TZ350

31st May 2023, 10:20

353203

We have been using a very handy 4L fuel bottle setup made by Speedpro for use on the Dyno. Worked very well but maybe time to up size the fuel line and fittings for Methanol.

353202

The inlet fitting is 5.5mm ID but the brass ball is 4.5mm so it looks like the cross drilling needs up sizing too.

F5 Dave

31st May 2023, 13:08

Drill it out and you may find the cross drill is 3.2mm or something silly. Then plug again checking that doesn't impede flow. I use a bolt cut down to 'not much', and Devcon. View down inlet to check.

On the 24mm flat mikuni the cross drill broke through to the outside world half way along so more Devon and Re-drill. Shouldn't be a problem on bigger carb.

Short tracks hide this often. Big tracks expose restrictions.

Sometimes through gears 1 to 6 with big roller like on dynojet I could see tall gears getting worse.

Larry Wiechman

31st May 2023, 15:04

We have been using a very handy 4L fuel bottle setup made by Speedpro for use on the Dyno. Worked very well but maybe time to up size the fuel line and fittings for Methanol.

I don't trust gravity to get the job done. A stack of diaphragm pumps and a pump-around system will keep the mainjet from sucking wind.

Flettner

31st May 2023, 18:04

Yes, I used a modified Honda 50 oil pump to pump E85 around a circuit, past the Lake Injector and back to the top of the tank. So as to keep a constant head of pressure no matter what fuel level was in the tank and to be sure there was fuel at the injector at all times.
I used a flat sided needle ( much like Smart Carb use ) but to tune Id solder, file and measure out at the track until I got the thing to run nice all throughout the rev range. Almost needed a little witchcraft to tune.

TZ350

31st May 2023, 18:35

353205

Up sized the fuel line and tap plus the float valve. Followed F5 Dave's suggestion for seating the float needle. Worked Ok.

Even with the bigger fuel line there were no apparent improvement to fuel flow, it still ran like a bag of Poooo with the hiccups. I will have to explore F5 Dave's suggestion about drilling out the cross drilling in the carb itself and get one of those float valves Wob suggested.

Otherwise I might have to look at Grumph's and Larry's idea of a fuel pump.

Also I found the cylinder base nuts had worked loose again! It had been reliable before I pulled it down for re balancing. I am surprised to be having this problem again. Are NordLock lock washers single use?

F5 Dave

31st May 2023, 18:56

Saw an interesting ooh-toob test on locking fasteners in weekend. Nordlock not covered. Found the old fashioned split washers were pretty good as were nylock (tested vold) and nuts with lock included. Those usual serated flange nuts often used on barrels were sub-optimal.

Grumph

31st May 2023, 19:23

Said it earlier when this problem came up - use Cone lock nuts. Do try it.....

Example - A sidecar outfit rear brake disc was continually coming loose with Nylocks on the retaining screws.

Cone locks fixed it.

husaberg

31st May 2023, 20:34

Now for the trick with the restricted flow to the float bowl. Driving WOT would cause a gradual drop in float bowl fuel level and an accompanying leaning of the mixture.
In the twisty parts of the track WOT would never take more than two seconds, but on the straight it would start making a difference.
Like I said, it was a risky business, and putting a hand over the carb would not do much good if the fuel level in the bowl was too low.

What good would an extra volume of fuel do if it is too low in the bowl?

One of the ways i used to establish it was too lean was to wind off the throttle a smidge whilst maxed out to see if it gained revs. If it did go richer
it must have momentarily enrichened it or just went to a less lean state. not sure which, but it used to work for me at least. But was never on the ragged edge.

jato

31st May 2023, 21:11

353205

Up sized the fuel line and tap plus the float valve. Followed F5 Dave's suggestion for seating the float needle. Worked Ok.

Even with the bigger fuel line there were no apparent improvement to fuel flow, it still ran like a bag of Poooo with the hiccups. I will have to explore F5 Dave's suggestion about drilling out the cross drilling in the carb itself and get one of those float valves Wob suggested.

Otherwise I might have to look at Larry's idea of a fuel pump.

Also I found the cylinder base nuts had worked loose again! It had been reliable before I pulled it down for re balancing. I am surprised to be having this problem again. Are NordLock lock washers single use?

Excluding safety, putting 3 or 4 psi of air pressure into the tank will encourage the fuel to head for the float bowl. it might help establish where the problem lies. wear goggles and overalls incase the tank doesn't like the idea...

DoldGuy

1st June 2023, 03:29

353205

Up sized the fuel line and tap plus the float valve. Followed F5 Dave's suggestion for seating the float needle. Worked Ok.

Even with the bigger fuel line there were no apparent improvement to fuel flow, it still ran like a bag of Poooo with the hiccups. I will have to explore F5 Dave's suggestion about drilling out the cross drilling in the carb itself and get one of those float valves Wob suggested.

Otherwise I might have to look at Larry's idea of a fuel pump.

Also I found the cylinder base nuts had worked loose again! It had been reliable before I pulled it down for re balancing. I am surprised to be having this problem again. Are NordLock lock washers single use?

TZ, why not use a Bigger Suitcase?
(Hopefully the pictures attached)

F5 Dave

1st June 2023, 07:18

That will only slow the problem down. The level will still always lower if the float needle cant let enough past to keep up with horrific consumption.

pete376403

1st June 2023, 09:01

You need an Amal GP with dual float bowls. Of all the problems possible, running out of fuel in the carb wont be one of them

lodgernz

1st June 2023, 09:43

Also I found the cylinder base nuts had worked loose again! It had been reliable before I pulled it down for re balancing. I am surprised to be having this problem again. Are NordLock lock washers single use?

https://www.theboltholder.co.nz/view-product/nuts/m8-cone-lock-nut-zp-cl10

jato

1st June 2023, 10:13

If you do go with those nuts from the boltholder you'll need to check the nut seat is true to the thread as every nut bolt and stud i've used from them in recent years has been miles out - aircraft quality is what's needed...

wobbly

1st June 2023, 10:14

TeeZee , the only reason the base nuts loosen off is due to gasket crush , created by detonation shock.
Maybe not enough to eat a piston but certainly enough to eventually kill bearing cages.

flyonly

1st June 2023, 10:34

353205

Up sized the fuel line and tap plus the float valve. Followed F5 Dave's suggestion for seating the float needle. Worked Ok.

Even with the bigger fuel line there were no apparent improvement to fuel flow, it still ran like a bag of Poooo with the hiccups. I will have to explore F5 Dave's suggestion about drilling out the cross drilling in the carb itself and get one of those float valves Wob suggested.

Otherwise I might have to look at Grumph's and Larry's idea of a fuel pump.

Also I found the cylinder base nuts had worked loose again! It had been reliable before I pulled it down for re balancing. I am surprised to be having this problem again. Are NordLock lock washers single use?

Do a flow test with the bowl off but with something limiting the drop of the float. This way you can check the flow of the system from the tap to the bowl. There is a guide on how much fuel you need to flow per minute per hp for petrol. I found with the bowl off it could flow enough but bowl on, the needle could not fully open

Sent from my iPhone using Tapatalk

wobbly

1st June 2023, 17:13

Yes Fly I agree , I had to lift the fluel level very high in the bowl , so the the floats would drop alot , pulling the needle well of the seat before bottoming on the floor.
TeeZee I do have a brand new Dellorto 4.2 Methanol float valve assembly you can have - the 55 Hp 125MX TM multi Championship 1 plate winner ,needed a 4.5 so yours should be fine with a 4.2.
I also have a screw adjustable powerjet that worked perfectly when its flow was equal to 25% of the main when set to 1/4 turns , and easy to access by hand on the fly to keep a consistent egt
with small adjustments in and out compensating for the changing weather RAD.

husaberg

1st June 2023, 18:01

You need an Amal GP with dual float bowls. Of all the problems possible, running out of fuel in the carb wont be one of them

This was due to downdraft angle. mk2 concentric's with matchbox gp floats for the quantal Norton Cosworth twin prior to it being converted to fuel injection
Surtess was the manager or something so i guess he had used or offered what he had or was familiar with.
353209
it also used a couple of 60's F1 Ferrari radiators or oil coolers it miht have been Ferrari oil collers as radiators
Grumph will remember

https://youtu.be/bsdERNI6cM8
But pretty sure this guy was the mechanic.
The best rider you have likely never heard of.
Son of the famous Bultaco importer Bert..

for you Greg

Cam profiles were originally lifted straight from the Cosworth DVA engine, with valve lifts and durations being equal, exhaust and intake, and set at 102 degrees maximum lift both. Maximum valve lifts were 10.4 mm, and at 1mm lift, durations were 274 degrees. Later Gary Flood changed these settings to give intake full lift at 98 degrees ATDC, but despite this early opening, no problem was ever found with valve to piston clearance. Later the intake cam was changed to one developed by John Judd when working with the Williams F1 team, which gave 1.5mm more peak lift.
Squish was set cold to 0,024 thou. but was found to shrink dynamically to 0.006 thou.

Duration looks to be the same as the CB700sc nighthawk at 1mm

The CB700SC was incredibility
276 deg at 1mm lift 120 lobe center for intake 118 for ex.
they must have put a hot can to make up for the 50cc lost due to US making to protect Harleys.

Flettner

1st June 2023, 19:29

Blah, floats, needles, jets. :laugh:

Grumph

1st June 2023, 19:38

Blah, floats, needles, jets. :laugh:

And of course, cams valves etc etc...

pete376403

1st June 2023, 20:21

This was due to downdraft angle. mk2 concentric's with matchbox gp floats for the quantal Norton Cosworth twin prior to it being converted to fuel injection

Aboout the time I started speedway the standard two valve Jawas carb was a DellOrto SS1. The hot setup was two remotely mounted bowls (even bigger than the pic of the Amal GP bowls I posted. I couldn't be bothered withthe continual adjustments so put on a 36 (38?) Mikuni and the thing would even idle.
However none of this is helpful wrt to TZ350s problem

husaberg

1st June 2023, 20:25

Aboout the time I started speedway the standard two valve Jawas carb was a DellOrto SS1. The hot setup was two remotely mounted bowls (even bigger than the pic of the Amal GP bowls I posted. I couldn't be bothered withthe continual adjustments so put on a 36 (38?) Mikuni and the thing would even idle.
However none of this is helpful wrt to TZ350s problem

i have two of those ss1's .......
if tz added a su float bowl it would have to be able to flow enough for half or a third of a jag 4.2
You should be able to mount it under the main jet?

bellow is an HS4
https://www.triumphexp.com/phile/8/32185/Float_bowl_and_jet_installation_01.jpg
Another view austin maxi these are rubber hose jointed and can be mounted anywhere at any angle of carb
353233353245353246

Said it earlier when this problem came up - use Cone lock nuts. Do try it.....

Example - A sidecar outfit rear brake disc was continually coming loose with Nylocks on the retaining screws.

Cone locks fixed it.

Are cone locks like the axel nuts on modern bikes?

Kickaha

1st June 2023, 20:27

Said it earlier when this problem came up - use Cone lock nuts. Do try it.....

Example - A sidecar outfit rear brake disc was continually coming loose with Nylocks on the retaining screws.

Cone locks fixed it.

Nylon melts, metal doesn't, not at those temperatures anyway, I always used cone locks on the LCR brakes If you want to be extra wanky use JetNuts/Kaynuts, they have a reduced hex size compared to others, expensive though

Condyn

2nd June 2023, 11:19

Are there any rules on transfer window minimum bridge width with iron lined cylinders? I have had success going to 2mm on 70mm bore cyls, but with nikasil. I would hate to hit the point of no return on the 99th hour of these hooers.

TZ350

2nd June 2023, 17:05

Drill it out and you may find the cross drill is 3.2mm or something silly. Then plug again checking that doesn't impede flow. I use a bolt cut down to 'not much', and Devcon. View down inlet to check.

Yep 3,3mm.

353212

I have now drilled it all out to 6mm including the brass fuel barb. The delivery fuel line is 8mm id.

353213

F5 Dave

2nd June 2023, 18:06

Was just a guess. No need for it to be any bigger said the engineers to themselves considering the target audience of these carbs. Like it's not likely they will be fitted to something that does less than 15km per litre!

Strokerhaus

2nd June 2023, 21:06

Hi TZ

I'm also trying to run 40+ rwhp on an aircooled single, but running on Avgas. So yes I do have temperature related power drop off, plus like you a cylinder bolt torque drop off.

I did work with my old friend the late Ron Gardner on Speedway bikes, and we could run the Gardner's (Lake, Lectron, Star, Posa, etc are all copies) without float chamber not recommended for anything other than speedway or high flow Gardner float chambers. The chambers are still available if required.

As for cylinder bolt torque drop off, I'm running M8 bolts which are right on, or in fact slight over their stress limit. I really should go one size up but currently lack the room.

Keep up the good work.

Frits Overmars

3rd June 2023, 03:50

It is Saturday, June 3 in Thailand :D
353220

Grumph

3rd June 2023, 07:16

Hi TZ

I'm also trying to run 40+ rwhp on an aircooled single, but running on Avgas. So yes I do have temperature related power drop off, plus like you a cylinder bolt torque drop off.

I did work with my old friend the late Ron Gardner on Speedway bikes, and we could run the Gardner's (Lake, Lectron, Star, Posa, etc are all copies) without float chamber not recommended for anything other than speedway or high flow Gardner float chambers. The chambers are still available if required.

As for cylinder bolt torque drop off, I'm running M8 bolts which are right on, or in fact slight over their stress limit. I really should go one size up but currently lack the room.

Keep up the good work.

What's your brand of problem ? There are to my knowledge (besides Rob's Kawasaki) people on here trying to extract unfeasible HP from aircooled Bultacos, Maicos and in my case AJS Stormer.

Flettner

3rd June 2023, 08:24

Electronic injection on E85, is the answer. Who cares what the question was😁. Great for air cooled engines.

wobbly

3rd June 2023, 08:33

Same question as why put a turbo on a Beetle.
TeeZee the bits are on the way to ESE , the carb as well , couldn't be arsed disassembling it.

F5 Dave

3rd June 2023, 08:37

Same question as why put a turbo on a Beetle.
. .
Because with any luck you will destroy it?
(Ducks for cover as the vdub fans rise and make farty noises in protest)

TZ350

3rd June 2023, 08:44

TeeZee the bits are on the way to ESE , the carb as well , couldn't be arsed disassembling it.

Thanks, very much appreciated.

Electronic injection on E85, Great for air cooled engines.

Electronic fuel injection would most definitely be 100% my choice for methanol but the class rules specifically forbid EFI for pre 72.

TZ350

3rd June 2023, 09:11

Hi TZ I'm also trying to run 40+ rwhp on an aircooled single, but running on Avgas. So yes I do have temperature related power drop off, plus like you a cylinder bolt torque drop off.

There are to my knowledge (besides Rob's Kawasaki) people on here trying to extract unfeasible HP from aircooled Bultacos, Maicos and in my case AJS Stormer.

From my Bucket experience with Suzuki GP125's 22 rwhp seemed the upper limit for consistent power on the track. Any more and the air cooling could not cope. I have thought of looking at using a small peristaltic pump to inject water and or emulsifying water with the fuel.

Injecting water really appeals to me because the Ignitec ignition can turn on a power jet or peristaltic pump at whatever rpm you like. So you could inject water into the inlet when the engine needs it most.

With 90% Methanol plus 10% Acetone and Caster927 oil 30:1 I can mix in 2,5% water easily and 5% if I leave it over night for the cloudiness to clear.

353221

I have tried mixing water directly with the fuel before but other pump fuel or Av gas and oils did not like the water but I might try again using 10% Acetone and Caster927. Easy to mix small batches for experimenting.

I researched a lot about hydrophilic and hydrophobic and various approaches to make them more cooperative.

F5 Dave

3rd June 2023, 09:55

Um. .. in what rulebook will that not be classed as water cooling?

Flettner

3rd June 2023, 10:24

There would be no rule against mechanical injection? After all Hillborn have been around way before 1972. With sneaky electronic control of the bypass jet..... perhaps.

husaberg

3rd June 2023, 11:06

There would be no rule against mechanical injection? After all Hillborn have been around way before 1972. With sneaky electronic control of the bypass jet..... perhaps.

With the rules from memory you have to prove it was in use on that sort of bike in the period the onus is on the person to prove eligibility or similar. buckets its open of course, but no alcomohol for them anymore.

(A) Pre 72 which shall consist of machines manufactured after January
1st 1963 and before October 30th 1972.
(B) Pre 82 which will consist of machines manufactured after the
closing date of the Period 1972 class and before December
31st 1982.
(C) Pre 89 which will consist of machines manufactured after the
closing date of the period 1982 class and before December
31st 1989.
(D) Pre 95 which will consist of machines manufactured after the
closing date of the period 1989 class and before December
31st 1995

Major Components:
Major components are: Frame (including Swingarm), Engine and Gearbox
castings, carburettors, Brakes (excluding front and rear master cylinders
which are open) and forks. These are to be manufactured between Jan 1st
1963 and December 31st 1995. Major components manufactured in any
country shall be acceptable. The onus of proof of eligibility shall rest wholly
upon the rider or entrant of the machine.
Modifications to major components are allowed, providing that such
modifications are visually indistinguishable from modifications proven to
have been used during this period. The onus of proof rests with the entrant
or rider of the machine

pre 72

17.3f Fuel Induction:
Fuel induction must be by way of period style carburettor of slide or
diaphragm type.
All carburettors are to be of square or round slide type, except for Gardner flat
slide carburettors. All flat side carburettors are otherwise banned. (Onus of
proof is on competitor rider or entrant of the machine).
Turbo and supercharging shall not be allowed.

that said it completely possible someone tried hillborne injection on a flat tracker in that period.
it was first used in 1949.
Last serious circuit bike i can remember using them was the 851 based BMS.
pretty sure the speedway and top fuel dragster still use it or similar.
watching the Nascar videos from the crew chiefs back in the day it looks like Nitros was a period mod for qualifying they just used to keep changing where they hid it.

PS happy birthday Jan thanks for sharing all your knowledge.

Grumph

3rd June 2023, 14:43

Um. .. in what rulebook will that not be classed as water cooling?

Ours actually. But a bigger concern is meeting fuel rules. i suspect a fuel with any appreciable water content won't pass the specific gravity tests.
It's either declared petrol or Methanol. There are specified ranges of SG for either fuel. Outside those it's illegal.

Strokerhaus

3rd June 2023, 21:56

What's your brand of problem ? There are to my knowledge (besides Rob's Kawasaki) people on here trying to extract unfeasible HP from aircooled Bultacos, Maicos and in my case AJS Stormer.

Mine is a Royal Enfield GP5, I saw the picture of your AJS it look beautiful!

You in the UK?

husaberg

3rd June 2023, 22:18

Mine is a Royal Enfield GP5, I saw the picture of your AJS it look beautiful!

You in the UK?

Do you run the original Albion gearbox?

Strokerhaus

4th June 2023, 00:15

Do you run the original Albion gearbox?

Hi Husaberg

Yes it has the 5 speed barrel cam Albion, but I have under cut the dogs, and I'm using a Greeves Griffin clutch.

The only issue I have had is the bronze bearing in the output gear needs to be replaced from time to time, the rest is fine.

Grumph

4th June 2023, 06:42

Mine is a Royal Enfield GP5, I saw the picture of your AJS it look beautiful!

You in the UK?

South Island of NZ - Christchurch. The Stormer is a little hamstrung in the gearbox area. Best i've got is a 4 speed close ratio. Around the time I built the bike for the first owner I had a converted Stormer through the workshop to finish the installation of one of the very rare 6 speed boxes. Apparently they only made around 100 of these. I asked FB AJS how much oil it took - and they'd never seen one. Had to contact one of their retired staff to get the information.

Interesting that the two motors are from about the same period and each identifiably the product of one man. The RE is largely Herman Meir and the AJS - well villiers really - is Bernard Hooper.

TZ350

4th June 2023, 08:44

Flettner

4th June 2023, 21:43

E85 still banned?

Strokerhaus

5th June 2023, 00:58

South Island of NZ - Christchurch. The Stormer is a little hamstrung in the gearbox area. Best i've got is a 4 speed close ratio. Around the time I built the bike for the first owner I had a converted Stormer through the workshop to finish the installation of one of the very rare 6 speed boxes. Apparently they only made around 100 of these. I asked FB AJS how much oil it took - and they'd never seen one. Had to contact one of their retired staff to get the information.

Interesting that the two motors are from about the same period and each identifiably the product of one man. The RE is largely Herman Meir and the AJS - well villiers really - is Bernard Hooper.

Herman was an interesting man, worked on loads of British two smokes.

As for Villiers gearboxes, there is a 6 speed box for sale on ebay.co.uk, but they want loads of money for it.

Grumph

5th June 2023, 08:07

E85 still banned?

Just petrol or methanol in the book. There's someone down here advertising E100.

I must ask the Tech Steward how it compares to the figures for meth next time I see him.

Someone really needs to put in a remit sorting the fuels situation. Methanol/ethanol should be equally acceptable.

Grumph

5th June 2023, 08:09

Herman was an interesting man, worked on loads of British two smokes.

As for Villiers gearboxes, there is a 6 speed box for sale on ebay.co.uk, but they want loads of money for it.

If it's the one I found, you get a complete bike for the money. 3500 quid with decent spares too.

husaberg

5th June 2023, 09:15

Herman was an interesting man, worked on loads of British two smokes.

As for Villiers gearboxes, there is a 6 speed box for sale on ebay.co.uk, but they want loads of money for it.

They certainly do thats $6,366.43NZD
i know there is only a finite amount of them made but i am picking the market is getting pretty small also.
353241353242353243

husaberg

5th June 2023, 09:25

Just petrol or methanol in the book. There's someone down here advertising E100.

I must ask the Tech Steward how it compares to the figures for meth next time I see him.

Someone really needs to put in a remit sorting the fuels situation. Methanol/ethanol should be equally acceptable.

But for different classes one or both
i think they have left it as e85 is whilst available at pumps somewhere, its not everywhere or extensively pump petrol is defined as any petrol to avgas
e85 benefits some bikes more than others ie air cooled or turbo.
Not sure why they only list methanol's characteristics the only posible advantage i could see is the small jet size neded

for on road racing its

Methanol as defined in Appendix D may only be used in the following
classes:
1. BEARS
2. Road Racing Classic as defined in Chapter 15.1
3. Classic Sidecars

The following classes shall have the choice of either petrol having
maximum characteristics not exceeding “Avgas, Unleaded FIM” or
methanol, both as defined in Appendix D.
Sidecars as defined in chapter 18. National Speed Records, Hill Climb –
Road-- Classic Road Racing as defined in chapter 15. Post Classic (Period
72) Road Racing as defined in Rule 17.3. Post Classic (Period 82) Road
Racing as defined in Rule 17.4. Post Classic (Period 89) Road Racing as
defined in Rule 17.5 (4 stroke engines only), 125 GP/250 Mono as
defined in Appendix G, BEARS.

Grumph

5th June 2023, 09:57

But for different classes one or both
i think they have left it as e85 is whilst available at pumps somewhere, its not everywhere or extensively pump petrol is defined as any petrol to avgas
e85 benefits some bikes more than others ie air cooled or turbo.
Not sure why they only list methanol's characteristics the only posible advantage i could see is the small jet size neded

for on road racing its

What would make more sense is to make E85 or E100 legal for those classes which can use methanol at present.
There is a price and availability difference depending on area. E85 is hard to get in the SI. Methanol isn't - but it's expensive.

I see no reason to change any of the regs relating to petrol. 100 testing the same as FIM 100 unleaded is available nationally.

Flettner

5th June 2023, 10:10

When are the bucket rules changing back to 100cc fourstroke..... open, as it used to be.
Or just amend the rules for 100cc fourstroke, may run E85, but all other classes remain the same.
Haha, limit 100 fourstroke to air cooling, I dont mind.

Vinduro are.... engine 'open' but must be air cooled and cc limit (fourstroke150cc). Fuel is open.

Flettner

5th June 2023, 11:31

Husa, you are good at finding shit like this, what has a 45mm fourstroke piston..... semi modern style. CL125? Two valve.

husaberg

5th June 2023, 11:34

Husa, you are good at finding shit like this, what has a 45mm fourstroke piston..... semi modern style. CL125? Two valve.

1mm oversize cb125t or cd125

https://www.tkrj.co.jp/goods/m-AH0670X-399-010.php

PISTON KIT
MODEL
CB-125T
CD-125T
OEM No. 399-010
CODE No. AH0670X
BORE(mm) ：Ａ 44
LENGTH(mm) ：Ｂ 48.4
PIN DIA (mm) ：C 13
COMPRESSION HIGHT① (mm)：D 24.9
COMPRESSION HIGHT② (mm)：E 21
PIN LENGTH (mm) ：Ｆ 34.5
PLATING
STROKE 4
PISTON　CODE No. PH0720

353244

Kickaha

5th June 2023, 12:17

They certainly do thats $6,366.43NZD

You could buy a brand new TT Industires box for that and it wouldn't be old worn out shit

Grumph

5th June 2023, 12:44

You could buy a brand new TT Industires box for that and it wouldn't be old worn out shit

True. But i've handled both and surprisingly the Villiers origin 6 speed is a nicer thing. Needle rollers right through it, not a bronze bush in sight.
The TT Ind boxes are better made, updated 1950's Norton copies. Nothing wrong with that behind a Manx or 7R.
Most of the Villiers boxes have sat on shelves for 50 plus years. Not a lot of the 100 or so actually made it onto track.

husaberg

5th June 2023, 13:53

True. But i've handled both and surprisingly the Villiers origin 6 speed is a nicer thing. Needle rollers right through it, not a bronze bush in sight.
The TT Ind boxes are better made, updated 1950's Norton copies. Nothing wrong with that behind a Manx or 7R.
Most of the Villiers boxes have sat on shelves for 50 plus years. Not a lot of the 100 or so actually made it onto track.

For a Greeves i was going to use a bolt on BSA box off a Plunger A10 (a common nearly bolt on mod)and to convert that to 5 speed it would 4G NZD for the NOVA and be one one gear down.
I think there was a 6 speed made for the std BSA box. Tonkin? but these seem to be unobtanium now.
Not sure on the price of a complete TT gearbox but they dont bolt up on the engine as a semi unit llke a STD one will and i would say they are 5-6g as well.

Kickaha

5th June 2023, 16:11

t.
The TT Ind boxes are better made, updated 1950's Norton copies. Nothing wrong with that behind a Manx or 7R.

They do about 6 different types of housing with 4 to 6 speeds, also some have kickstart and speedo drive options

Not sure on the price of a complete TT gearbox but they dont bolt up on the engine as a semi unit llke a STD one will and i would say they are 5-6g as well.

Around 6g for a BSA 5 speed with kickstart and speedo drive which is what I bought for mine

husaberg

5th June 2023, 19:19

this is interesting
353252353253
https://thunderproducts.com/dial-a-jet-remote-float-bowl-kit-for-efi-alcohol-snow-tech-magazine/
https://thunderproducts.com/product/remote-float-bowl/

https://thunderproducts.com/product-category/fuel-systems/carb-jets-accessories/

Also some mods for downdraft
https://motochassis.com/FileDump/AmalMk2.pdf

lohring

6th June 2023, 02:06

A long time ago we ran fuel tests on our industrial style race engines. We tested various "pump gasolines" to check alcohol content. The first fuel was 87 octane gasoline with no additives. This will pass the standard Digitron test for additives used in APBA and other professional racing. We purchased some Coleman camp fuel at Walmart that also contained no alcohol. Some Union 76 92 octane premium gasoline contained 8% alcohol. Fuel advertised as E10, supposedly containing 10% alcohol, actually was 32% alcohol. E85, purchased at the same station and advertised as containing “at least 70% ethanol”, was only 60% alcohol by our test. We ran a single pipe that was not adjusted for different EGT from the various fuels. In our fixed ignition, low compression engines the fuel made no power difference.

Lohring Miller

Strokerhaus

6th June 2023, 04:39

If it's the one I found, you get a complete bike for the money. 3500 quid with decent spares too.

The one I saw was the one Husa found, but if the other is better great.

I was up seeing a friend who runs Villiers 210 Karts which put out serious power, he has managed to get the old road gong Villiers box to last a season, Maybe worth talking to, he said the Starmaker 4 speed box was way better than the standard road box. His name is Simon Bateman from Nametab Engineering here in the UK.

Best of luck

Grumph

6th June 2023, 06:17

The one I saw was the one Husa found, but if the other is better great.

I was up seeing a friend who runs Villiers 210 Karts which put out serious power, he has managed to get the old road gong Villiers box to last a season, Maybe worth talking to, he said the Starmaker 4 speed box was way better than the standard road box. His name is Simon Bateman from Nametab Engineering here in the UK.

Best of luck

Yes, I've heard of the company. Never dealt with them. I've been there with Villiers road boxes. An earlier 197 special split a 3 speed case - as you do. It finished up with a 4 speed box from a Greeves which took a bit of fettling to make fit. Lasted OK. I'll stick with the CR 4 speed for the moment. In it's class it's not a great handicap.
If a six speed falls into my hands, great. If not, I'm only doing it for fun.

ken seeber

6th June 2023, 21:21

2B or not to be??

The beauty of taking so long is that you don't have to rush for the next stage...:clap:

353277

SwePatrick

7th June 2023, 05:47

Need to backup my info on tuning twostroke with o2 sensor.

Do you guys compensate for air in exhaust at full throttle in your twostrokes?

I have just installed the o2 sensors in my dyno and made a testpull.
It was rock solid 11.86 AFR up to peak torque, and leaned out to about 12 at peak power.(e85 fuel)
Really happy with that stability and fuel curve, but as i know there are some unburnt oxygen in exhausts i figure i actually run it a little bit rich(safe), and my plugs verify that.

So my qustion is, do you have some rule of thumb?
Like this: 12.0 in afr is actually 11.5
My sensors are located in the endcone about 8cm upstream from stringer.

Rgds.

wobbly

7th June 2023, 12:37

The Lambda is telling you what is actually happening , if its leaning slightly up top but is perfect everywhere else than a slightly smaller main air compensation with a slightly bigger main will flatten out the curve up top
but keep the rest the same.
This effect up top could also be an artifact of excess timing retard past peak torque - the fix for having to go rich on the main to keep the egt or Lambda correct is to flat line the ignition at that point.
I dont know what the best dyno power egt or Lambda is on E85 but you should , before making decisions on jet changes.
As maybe this scenario is perfect ie slightly rich in the mid , cooling the pipe , then slightly leaner up top , heating the pipe and making it rev.

SwePatrick

8th June 2023, 07:14

Yes, and i´m very suprised that it was rocksolid with very little fluctuation, almost none, just that smooth leaning up against revlimiter from peakpower.
But i figure it will be more if i measure at cruising speed, and not full throttle.

E85 fuel is happy at around 0,78-0,82 Lambda, and even as it is alcohol it isn´t fancy of more ignition, altough it can take it.
I only use it as an extra safety from detonating and it runs about 100-150c cooler in exhaust, less heatproblems.
And actually some powergain, about 6-8% if tuned correctly.

But my question was that maybe someone has seen a pattern in how much they report wrong value due to unburnt air in exhauststream.

I´m using this 'adapter', this one should make lifespan a little bit longer, i will not leave sensors in exhausts outside dyno.
So i figure they can take a couple of runs, fun fact : it is the same sensors as in my two mercedeses, so i´ve got in total 6 sensors(4 spare) as i´ve replaced them on my cars.

353281

wobbly

8th June 2023, 08:19

The Lambda channel may have alot of data smoothing on it in the software.
This makes a huge difference to the Hp curve info , where you can have a dead smooth printout with hardly a bump anywhere , or a scattered trace with ups and downs over very short rpm intervals.
Lambda only reads the excess O2 in the combustion gas residuals , and this is then converted into a A/F ratio for ease of understanding , I dont think any fudge factor for the different fuel is needed.

husaberg

8th June 2023, 18:45

2B or not to be??

The beauty of taking so long is that you don't have to rush for the next stage...:clap:

353277

Hamlet had a stab at it but from memory got Polonius instead of Claudius.

lohring

9th June 2023, 02:10

Below is a stinger lambda adopter sent to me by Del a long time ago.

Lohring Miller

353288353289353290

SwePatrick

9th June 2023, 06:51

The Lambda channel may have alot of data smoothing on it in the software.
This makes a huge difference to the Hp curve info , where you can have a dead smooth printout with hardly a bump anywhere , or a scattered trace with ups and downs over very short rpm intervals.
Lambda only reads the excess O2 in the combustion gas residuals , and this is then converted into a A/F ratio for ease of understanding , I dont think any fudge factor for the different fuel is needed.

I ´m very well aware of how an o2 sensor works, and it is because of this i know there is a problem.

I´m not asking for difference in fuels.
I´m asking for a general 'fudgefactor'.

SwePatrick

9th June 2023, 06:52

Below is a stinger lambda adopter sent to me by Del a long time ago.

Lohring Miller

353288353289353290

Nice, it´s a unverisal one?
One size fits all?

lohring

10th June 2023, 02:36

You can change the rubber disk if you need to fit a larger stinger. Our stingers are around 1/2" OD Below is a pictire from the drawing file.

Lohring Miller

353296

lodgernz

10th June 2023, 11:03

I have this Daytona cylinder for my NSR50 engine. It has auxiliary exhausts, but they are terrible.
They open at or earlier than the main port, but I'll be raising the main anyway, so that's not an issue.
I'm going to have the cylinder bored and replated after I've worked on it, so any mods are possible within the limitations of wall thickness etc.

My main problem is the poor placement and size of the aux ports, so I'm asking here for advice on how best to improve them

353298353299353300353301

wobbly

10th June 2023, 13:01

Trust me , get the chrome off before you start , makes porting 100% easier.
Cant believe how bad those angles are , but here is a few pointers - most important is getting the A port front wall angled back.
Somewhat depends upon getting a piston pinned at the rear to get the B port wide enough with rear wall hooks in place.
I would go for reverse stagger scavenging , so you can leave the A port timing edge alone , and do an analysis on how much transfer STA you need to match the much bigger Ex STA.
As a guide you want as a minimum 1mm of height difference between the Aux and the main Ex.
What is the 37* angle for the boost , is that the floor inclination ?

Frits Overmars

10th June 2023, 18:40

Cant believe how bad those angles are , but here is a few pointers - most important is getting the A port front wall angled back.My thoughts exactly. Maybe this can be of some help:
353307

lodgernz

12th June 2023, 11:53

Trust me , get the chrome off before you start , makes porting 100% easier.
Cant believe how bad those angles are , but here is a few pointers - most important is getting the A port front wall angled back.
Somewhat depends upon getting a piston pinned at the rear to get the B port wide enough with rear wall hooks in place.
I would go for reverse stagger scavenging , so you can leave the A port timing edge alone , and do an analysis on how much transfer STA you need to match the much bigger Ex STA.
As a guide you want as a minimum 1mm of height difference between the Aux and the main Ex.
What is the 37* angle for the boost , is that the floor inclination ?

The boost port angle is the roof angle, so that needs to go to 56º.
I understand the transfer mods required, I was mainly wondering how to improve the tiny aux exhausts, so your diagram is a good guide.
Thank you Wobbly and Frits.

Wos

15th June 2023, 22:22

I have this Daytona cylinder for my NSR50 engine. It has auxiliary exhausts, but they are terrible.
They open at or earlier than the main port, but I'll be raising the main anyway, so that's not an issue.
I'm going to have the cylinder bored and replated after I've worked on it, so any mods are possible within the limitations of wall thickness etc.

My main problem is the poor placement and size of the aux ports, so I'm asking here for advice on how best to improve them

353298353299353300353301

???
On the photo the upper side of exhaust Window...its radiuses look huge...!???

Good für ring life
Bad for blowdown

Proof it and use the exhaust advices from Frits ;)

lodgernz

16th June 2023, 09:38

This is a nice restoration job by a Dutch enthusiast

353332

Strokerhaus

18th June 2023, 05:12

Yes, I've heard of the company. Never dealt with them. I've been there with Villiers road boxes. An earlier 197 special split a 3 speed case - as you do. It finished up with a 4 speed box from a Greeves which took a bit of fettling to make fit. Lasted OK. I'll stick with the CR 4 speed for the moment. In it's class it's not a great handicap.
If a six speed falls into my hands, great. If not, I'm only doing it for fun.

Hi

I have just come across a DMW Hornet all in pieces with rebuilt Starmeker and 6 speed box, less front wheel, exhaust and one other thing, which I can remember but not a big item, I suspect you could get it for less than £4000 if you wanted it. Interested? If you are I will try to link you up with the owner.

Grumph

18th June 2023, 06:30

Hi

I have just come across a DMW Hornet all in pieces with rebuilt Starmeker and 6 speed box, less front wheel, exhaust and one other thing, which I can remember but not a big item, I suspect you could get it for less than £4000 if you wanted it. Interested? If you are I will try to link you up with the owner.

A kind thought - but freight to NZ would probably double the cost. I'll pass thanks.

Niels Abildgaard

20th June 2023, 06:17

I dreamt up a two stroke sidevalve concept 23 dec 2014 and now somebody has taken it up.
Could maybe have saved the Orbital thing.

https://www.modelenginemaker.com/index.php/topic,4547.msg268833/topicseen.html#new

TZ350

20th June 2023, 14:01

TeeZee the bits are on the way to ESE , the carb as well , couldn't be arsed disassembling it.

353352

Thanks Wob. The carb turned up today. That adjustable power jet looks very interesting. I will use it.

353351

Now to see if I can find a way to fit the 4,2mm ID Dellorto float valve into the Mikuni carb. Replacing the Mikuni 3,3mm ID float valve.

The challenges are that the Dellorto float valve has a 8mm diameter thread and is 22,5mm long. The Mikuni has a 10mm thread and is 18,5mm long.

353353

There might be more than one way to to do this. The Dellorto float valve needle is the same length as the Mikuni. I could open the 3,3mm ID Mikuni float valve body out to 4,5mm and use the Dellorto needle. There have been a few suggestions on here about improving the flow out of the Mikuni float valve body itself. And F5Daves suggestion of using a ball bearing ball and punching it to form the valve set seems to work. I have a few Mikuni float valves so it could be worth a try.

Larry Wiechman

20th June 2023, 15:52

https://www.freepatentsonline.com/3424431.pdf