ESE's works engine tuner

[SwePatrick]

do you have a chance to try nitro 30% ?

Ofcourse we have, but we will take it easy at first and try to reach 80hp on Methanol only first.

[philou]

Luc certainly invested a lot of money in the ryger.
For this reason he is not happy

[husaberg]

Beside everyone here should know what I wrote about calculate the Ryger principle.
And if you forgot, than read it back, for I don't want to repeat it every time again and again, because people cannot read well or had a bad memory.
Which is often followed by the same not smart suggestions as above and also shows a very bad insight in what realy happend inside a 2stroke engine.


Wobb,
I'm still waiting on your reply !

Luc I asked you in plain language that the ryger was foolishly over-hyped and or you lied and made up the Ryger calculation for 70HP and 30,000 RPM and 80% less emissions?
Or you were wrong? or you were both lying and were wrong?
Or are you trying to say you never posted these claims.

342081342082342083
Its a very easy question for someone to answer but most conmen don't answer simple questions, they just change the subjects.
Maybe you were too busy patting yourself on the back about questions i never asked, to notice or were you not answering the questions i did? or was it on purpose?

Just to reacquaint you with the claims here is the Dyno chart you posted that indicated that the Ryger 125 achieved 70HP, was this pure fantasy on your part.
Your claims were some 15HP higher than a RSA Aprilla achieved,was this made up.
342085342084

[speedpro]

I don't know why you bother.

Wobbly has the idea

[sb07]

My calculations are exactly the same as the Aprillia RSA.
And if you were one of my 23.000 folowers on YouTube or Facebook, than you could have read that many times.
Even stronger !! Since 2008 "my calculations are based on the Aprillia RSA" exept for one thing.
Jan was not free to choose his own exhaustpipe and he knows that I did correct that.

Beside everyone here should know what I wrote about calculate the Ryger principle.
And if you forgot, than read it back, for I don't want to repeat it every time again and again, because people cannot read well or had a bad memory.
Which is often followed by the same not smart suggestions as above and also shows a very bad insight in what realy happend inside a 2stroke engine.

A graph which is basic for my calculations:
https://www.facebook.com/photo.php?fbid=10203245604219984&set=a.1992436069636&type=3&theater

More about my calculatios:
https://www.facebook.com/luc.foekema/media_set?set=a.1992436069636&type=1&needsRefresh=true



the problem is that with the theory you don't win! :msn-wink:

[lucf]

I think I will back of 2* degrees on ex duration, stagger transfer opening, try to hook the a-port even more and then back on the dyno.

You think a possible cause is that the axial angles has increased flow quite some and in combination with a more effective diffuser due to higher ex duration is making it overscavenge??

rtechracing,
When using the right calculation, you know exactly what you have to do and need not to think about what you are going to do.

That's what we did 50 years ago !!

I have seen many examples how tuners are busy to search for the right pipe and in the end came to me with questions.
See this example: https://www.facebook.com/notes/luc-foekema/searching-for-power-in-a-2-stroke-can-become-a-long-way-/10200785536639832

Even very well known tuners who asked me in 2017, why do I have to set my ignition suddenly 8? earlier?
And yes I know directly and it shows also that many tuners even well known don't have the answer?

[Peter1962]

Luc I asked you in plain language that the ryger was foolishly over-hyped and or you lied and made up the Ryger calculation for 70HP and 30,000 RPM and 80% less emissions?
Or you were wrong? or you were both lying and were wrong?
Or are you trying to say you never posted these claims.

342081342082342083
Its a very easy question for someone to answer but most conmen don't answer simple questions, they just change the subjects.
Maybe you were too busy patting yourself on the back about questions i never asked, to notice or were you not answering the questions i did? or was it on purpose?

Just to reacquaint you with the claims here is the Dyno chart you posted that indicated that the Ryger 125 achieved 70HP, was this pure fantasy on your part.
Your claims were some 15HP higher than a RSA Aprilla achieved,was this made up.
342085342084

As usual, you will not get an answer...

[lucf]

As usual, you will not get an answer...


The subject here was how to calculate in the right way a 2 stroke without getting a wrong results as rtechracing


And the annoying way of asking questions by you and many others has ruled out ever speaking about Ryger here.
You are better off with guessing, because you are very good at that.

[husaberg]

The subject here was how to calculate in the right way a 2 stroke without getting a wrong results as rtechracing
And the annoying way of asking questions by you and many others has ruled out ever speaking about Ryger here.
You are better off with guessing, because you are very good at that.
What do you have to hide, you cant claim to be international expert without answering simple questions about the stuff you posted.
You cant claim now to be an expert on computer calculations and yet refuse to answer how your calculations were over 35HP and 15000 rpm's out.
My cat could have done better and to be frank, hes even by his own admission, rather useless at maths.
I remember the time you claimed to have contacted me via PM and i had agreed not to release Harry Rygers real name Hendrik Gerrits.
Only problem was no such messages or conversations ever occurred. It was just another fable of yours.
Kiwis dont like con artists take the hint and leave and go just back to your claimed thousands of adoring masses at facebook and youtube.
You clearly dont need to post in KB you are clearly far to clever for the likes of us, besides we prefer real people with real knowledge.
You are not even 0.2% of Jan or Frits even using your 50% optimistic plucked outr of thin air dyno

[F5 Dave]

Lucf you clearly have some serious personality disorders to work through. This is not a therapy group. Try seek some professional help but please leave us to our own devices.

We are not impressed by your lame "oh I have something wonderful in my pocket but you can't see it" children's game.

[Flettner]

Profile, left and right. Wiring time.

[F5 Dave]

Couldn't have used an old KTM Tshirt?

[Flettner]

Couldn't have used an old KTM Tshirt?

Yeah, should have. ����. certainly if I had a KTM Tshirt I would have no problems cutting it to little peices wirh the sizzors or razor or just stab it with a screwdriver.
Too much?

[Flettner]

Frits, you talked about how the blowdown requirement was different for methanol / ethanol engines, once. Model aircraft engines. Or was I mistaken?

[husaberg]

Yeah, should have. ����. certainly if I had a KTM Tshirt I would have no problems cutting it to little peices wirh the sizzors or razor or just stab it with a screwdriver.
Too much?

Do you have sheep or alpacas flet that fence looks well higher than the average Romney.
Is it due to alpacsas being more fire retardent due to the lack of lanolin:whistle:
Nice Stuff, I especially like the repackaged pipe

[ken seeber]

Do you have sheep or alpacas flet that fence looks well higher than the average Romney.
Is it due to alpacsas being more fire retardent due to the lack of lanolin:whistle:
Nice Stuff, I especially like the repackaged pipe

Jeez, as an Ozzie I thought it would be so much more politically correct to not take the piss out of kiwis about the ?sheep on the cliff edge? etc. However, it is now clear that this etiquette is no longer necessary. :2thumbsup

[rtechracing]

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

Thanks a lot guys!!

[lucf]

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

Thanks a lot guys!!

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

[Frits Overmars]

Can some of you guys that keeps asking questions about what Luc have said or claimed give me a good theory why the power drops before entering powerband like the dynograph shows?I'm not one of the "guys that keep asking questions about what Lucf has said or claimed" (god forbid!) but I'll give it a try.
When an engine runs at the rpm of maximum torque, the exhaust pipe pulses work in harmony with the port timings. A suction pulse from the exhaust pipe sucks fresh mixture out of the cylinder, filling the exhaust duct with it. After the transfer ports have closed again, a return pulse from the exhaust pipe pushes this mixture back into the cylinder, raising the mass of combustible mixture there. And then the exhaust port closes, capturing the cylinder contents.

But a 2/3 of this rpm it takes longer for the ports to close, while the exhaust pulses still move with about the same velocity as before. When he return pulse pushes the mixture back into the cylinder, the transfer ports are still open, so the cylinder contents flow back into the crankcase. Then the transfer ports close, leaving the crankcase pressure high instead of low, which is bad for the next inlet phase.
Next, the exhaust return pulse is reflected back from the cylinder, turning into a suction pulse, while the exhaust port is still open, so fresh mixture that was still present in the cylinder, is sucked out. And then the exhaust port closes, leaving hardly any combustible mixture in the cylinder. Hence the torque dip at 2/3 of max.torque rpm.

[rtechracing]

I was not aiming at you Frits and thanks a lot for your reply.
I noticed black residues downd the transfer ducts. So the solution will be to back of ex duration? If so, does it make sense to back of a litle each time to sort of find the limit where the duration makes more hp then anglea area.....I dont know if that make sense. 😊😊

[jonny quest]

Finding your optimum ex duration is easy. Start at 190 degrees, dyno, go to 191, dyno, 192, dyno... until things get wacky.

Easy ;P

[jonny quest]

I want to know why some engines lose power when going from a straight pipe to a pipe fit to the chassis. While others don't care how many bends are twists there are

That's a question I've yet to solve, nor heard of the reason

[Flettner]

The tank, suitable for E85 and the last of the mechanical stuff, the left hand kick start / bob weight. Cut the teeth and machine up a case to fit it all into.

Sheep? nah got rid of those fly blown, garden destroying ( when someone forgets to shut the gate) , one even had a drink problem, always trying to suck on the ethanol fuel line to my furnace, bags of wooly sheep poo. Kiwis, we love our sheep aye.

[Frits Overmars]

I noticed black residues down the transfer ducts. So the solution will be to back of ex duration? If so, does it make sense to back of a litle each time to sort of find the limit where the duration makes more hp then anglea area...Black residue in the transfer ducts usually indicates insufficient blowdown time.area: when the transfers open, the pressure of the spent gases in the cylinder is still above the pressure in the transfer ducts, so exhaust gases enter those ducts. Backing off exhaust duration would only reduce the blowdown time.area, aggravating the problem. Backing off the rpm on the other hand would increase the time.areas. In other words: don't rev quite so high.

Note: backing off the exhaust duration a little each time is like trying to drill a hole smaller... I'd rather follow Jonny Quests proposal of increasing the exhaust duration in small steps. That way you only need to bin one cylinder after you've exceeded the optimum. And you will have to: the only way to establish a limit is to exceed it.

[peewee]

hey frits what about widening the port as much as logically possible before raising the roof to the clouds :laugh:. perhaps rtech power loss is from the power stroke being reduced a bit to much, which seems like it would meen less cylinder pressure at exh open and less pressure differential between cyl and pipe, (less suction and plugging ) ?

[Frits Overmars]

hey frits what about widening the port as much as logically possible before raising the roof to the clouds :laugh:. perhaps rtech power loss is from the power stroke being reduced a bit to much, which seems like it would mean less cylinder pressure at exh open and less pressure differential between cyl and pipe, (less suction and plugging ) ?In general widening any port trumps raising it, but widening the exhaust port will also increase the risk of short-circuiting, especially with those H2-transfers.

I don't follow your reasoning about reducing the power stroke. Raising the exhaust roof means opening the exhaust port earlier, when the cylinder pressure is higher, generating stronger pipe action.

[jonny quest]

In general widening any port trumps raising it, but widening the exhaust port will also increase the risk of short-circuiting, especially with those H2-transfers.

I don't follow your reasoning about reducing the power stroke. Raising the exhaust roof means opening the exhaust port earlier, when the cylinder pressure is higher, generating stronger pipe action.

And that's why you fill in the A ports with epoxy by the ex port to shape them like modern A ports. A right trapezoidal shape.

[peewee]

frits if the spark lead is at 15atdc there must be a limit to how high the port could be. otherwise going beyond the limit, wouldnt the egt go down because the port opens before combustion gets far enough along ? and cyl pressure goes down as well because again , combustion process is still to early. thus less pressure difference between cyl and pipe ? maybe rtech is already beyond the limit

[TZ350]

... if the spark lead is at 15atdc ...

15 deg ATDC. is that a realistic thing???

[Grumph]

15 deg ATDC. is that a realistic thing???

You wouldn't think so - But Irving quotes the range of movement given to outboards with coupled throttle and ignition controls as varying from 35deg before to 10deg after TDC...So special circumstances can alter cases. But not, I would think, on an H2.

[TZ350]

.
Took the GP/NSR110 beast apart tonight. Been getting hot. It happens when you forget to turn the fan's on ...... :laugh:

I am impressed by the way this thing survives a good overheating.

Also, reeving it way past its blow down limit with excessively retarded ignition and lean mixture looking to get big over rev did not help. Plenty of burnt goo in the transfers. With EFI and its precise fueling I was able to extend the over rev way past anything I have been able to do with a carb.

I just love this engine, its a real trouper.

342117342118342119

[HenkS]

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


I would definitely try it
But I hope that you will post the result here anyway

[peewee]

15 deg ATDC. is that a realistic thing???

i meent btdc:yes:

[TZ350]

You wouldn't think so - But Irving quotes the range of movement given to outboards with coupled throttle and ignition controls as varying from 35deg before to 10deg after TDC...So special circumstances can alter cases. But not, I would think, on an H2.

With my water cooled Beast I have a range of 28 BTDC to near zero to get heat in the pipe, but I am not to sure its that good for the engine.

[TZ350]

Finding your optimum ex duration is easy. Start at 190 degrees, dyno, go to 191, dyno, 192, dyno... until things get wacky. Easy ;P

Did this on the air cooled engine and the interesting thing was, that the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.

[jonny quest]

Did this on the air cooled engine and the interesting thing was, that the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.

Yep... it's a very fine line when you get there. And then when you first get in the "wacky" zone... you mess with transfers to see if power starts to come back.

[Frits Overmars]

Frits, you talked about how the blowdown requirement was different for methanol / ethanol engines, once. Model aircraft engines. Or was I mistaken?Sorry for my late reaction Neil. Somehow I must have overlooked your question yesterday.
The blowdown requirement for those model engines is not different because of the fuel, but because of the way it is distributed (relatively big blobs), because of the very short time available for evaporation and because of the dreadful glowplug ignition.
Because of all these factors the combustible mixture in these engines needs to be preheated by way of Exhaust Gas Retention. If you give them a 'proper' blowdown,
they become very temperamental. And in a glowplug engine without permanent external heating one missed firing cycle can mean a total engine stop and a lost race.



frits if the spark lead is at 15atdc there must be a limit to how high the port could be. otherwise going beyond the limit, wouldnt the egt go down because the port opens before combustion gets far enough along ? and cyl pressure goes down as well because again , combustion process is still to early. thus less pressure difference between cyl and pipe ? maybe rtech is already beyond the limitYou had me searching for quite some time: "Where on earth did I write 15˚ aTDC?" But that has been cleared now.
Nevertheless your original question deserves a reaction.
WOT combustion may take somewhere between 43˚ and 60˚. Ignition delay is the time or the number of crankshaft degrees between the occurence of the ignition spark and the first instant when a temperature and a pressure rise because of combustion can be observed.

I took the values of the Aprilia RSA and a more mundane 125 cc engine for comparison.
Power @13000 rpm . . . . . . . . 54 . . . . . . . . . . . .40
ignition timing bTDC . . . . . . . .14˚ . . . . . . . . . . .18˚
ignition delay. . . . . . . . . . . . . .7˚ . . . . . . . . . . . .9˚
combustion duration . . . . . . . 46˚. . . . . . . . . . . 60˚
combustion completed aTDC . .39˚ . . . . . . . . . . .51˚

You can see that, even for the relatively slow-burning 'mundane' engine there is no combustion any more at 51˚ aTDC.
Its exhaust timing would have to be at least 260˚ before you could hope to see a glipse of a flame in the exhaust port.



... the difference between ultimate "good" and "wacky" was about the thickness of one 0.5mm cylinder base gasket. For my engine, 200 deg Ex duration = good, 204 = wacky. Take the base gasket out and we are back to good.Did you keep the compression ratio and the squish gap constant during these gasket changes? Changing the squish gap 0,5 mm can have the same effect as changing the ignition timing several degrees.

[SwePatrick]

because you are very good at that.

*lol*, that means we guessed right :D :D :D

[lucf]

I would definitely try it
But I hope that you will post the result here anyway

Yes, you will see, were many other needs much text bla..bla (good or bad)
I need only one calculation and tell him exactly what to do.
I did this in the past years more than 1500 times, one of them was a super kart:

TM K9c in the European Cup Superkarts at Hockenheim, april 2012

The experiences of a team that rides for the European Superkart Championship. Rider Fokko Zoutman in a kart with two 125cc TM K9c motors, one at each backwheel. No usual setup, but proven effective. The team asked me in the end of 2011 or improvements are possible, on standard factory concept initially for the exhaust and combustion chamber. In the calculation I soon discovered that, oddly enough, the original factory exhaust was not optimal for the cylinder, so the answer was soon ready. Also a significantly improvement to the combustion chamber was possible. Actually I found that the cylinder itself should be updated too, but one wanted to keep it unchanged at that moment.

feb 17, 2012 (after approx 2 months)
Hi Luc,

We have already tested on a short runway kart engines at circuit Pottendijk. This was a good test. On the long course, it may be different of course. Full throttle for much longer straights. We will see. I keep you informed what will happen. Greetings, Henri Tiben

April 20, 2012
Hello Luc,

Still getting better. The rider is now a European Championship race in Hockenheim. We can take on with the fastest speed in the whole field. The driver should be a little better, but that is on the driver. It's been laughing about how they talked in the padock that he can just have it right away by the fast guys. Greetings, Henri Tiben

One calculation . . . . ! (no bla bla, no gessing ! )

[Frits Overmars]

. Took the GP/NSR110 beast apart tonight. Been getting hot. It happens when you forget to turn the fan's on .. I am impressed by the way this thing survives a good overheating. So it didn't seize and the piston crown didn't cave in, but how about the piston ring? I've seen engines that ran hot with no apparent ill effects, only they were a pig to start afterwards: the piston rings had lost much of their tension.

[TZ350]

Did you keep the compression ratio and the squish gap constant during these gasket changes? Changing the squish gap 0,5 mm can have the same effect as changing the ignition timing several degrees.

I did my best to keep the compression ratio and squish the same.


So it didn't seize and the piston crown didn't cave in, but how about the piston ring? I've seen engines that ran hot with no apparent ill effects, only they were a pig to start afterwards: the piston rings had lost much of their tension. Things like that can keep you searching for days.

Thanks for the heads up, the ring certainly did look a bit limp.

[teriks]

Profile, left and right. Wiring time.
Cool, that's a very different layout for a dirt bike!
What will you do with the intake side? Seems like quite a challenge..

[Flettner]

Cool, that's a very different layout for a dirt bike!
What will you do with the intake side? Seems like quite a challenge..

The plan is to cast a new side case with a sealing flange (a bit like old Kawasaki RV engines) so I can cover the whole inlet / throttle drive, with perhaps a chance to try my hand at some carbon fiber to make a nice light cover. The airfilter will be where the radiator once was. Even with this side cover it will still be thinner than a standard YZ if you include the YZ's chamber at that point. This set up will be good enough to run round the yard and dyno with just a pod type air filter hose clipped on. Still a wee bit to do.

[Flettner]

Thank you Frits, I couldn't remember the exact details.
Thought I might be down some 'quantum physics' STIC worm hole.

[TZ350]

So it didn't seize and the piston crown didn't cave in, but how about the piston ring?

In the tradition of Bucket racing.

For the price of a new ring, I got these beauties off a Japanese auction site, seven NX4 piston assemblies. These had been religiously changed at Honda,s (money making) suggested maintenance intervals. These will be great, they are like new and will be good for all sorts of experiments, like radius-ed timing edges. Any one of them will run for ages in my Bucket, or at least until I over heat it again, but then I do have a few spares.

342139

[F5 Dave]

Ooh, do they come with circlips fitted?
Do you realise if you repack an old muffler and its really oily you can squeeze that right back into the oil container? :msn-wink:

They smear the ring lands over where the bridge bears. Check there for ring freedom.

[TZ350]

Do you realise if you repack an old muffler and its really oily you can squeeze that right back into the oil container? :msn-wink:

Ok "waste not, want not" it is,
I was't going to tell everyone that tip about recycling the oil, it was supposed to be our little secret, but you blabbed ..... :finger:.... :D

Thanks for the reminder about the ring lands, I will check them.

I love Bucket racing. :scooter:.

[Brett S]

Here's a hot Bucketeering tip, put anti seize on your piston skirt to stop it seizing.:2thumbsup

[speedpro]

Do you realise if you repack an old muffler and its really oily you can squeeze that right back into the oil container?

Whatever you do don't use something flammable to pack a muffler. Learned not to do that after covering the floor at dynotech with little pieces of flaming material

[TZ350]

Here's a hot Bucketeering tip, put anti seize on your piston skirt to stop it seizing.:2thumbsup

We have plenty of that, but I could do something better:-

Super Finishing and Stealth Coating:- https://www.facebook.com/pg/SuperFinishingLtd/photos/?ref=page_internal now that is some slippery shit.

The plant is real close to us and did a piston assembly for me the other day. My motor has the rod assembly, bearings, gearbox and rotary valve have all been super finished and stealth coated.

342149 342150

[F5 Dave]

Whatever you do don't use something flammable to pack a muffler. Learned not to do that after covering the floor at dynotech with little pieces of flaming material
Hahaha, Chris had carpet in there too.:nya:

[flyincat]

You had me searching for quite some time: "Where on earth did I write 15* aTDC?" But that has been cleared now.
Nevertheless your original question deserves a reaction.
WOT combustion may take somewhere between 43* and 60*. Ignition delay is the time or the number of crankshaft degrees between the occurence of the ignition spark and the first instant when a temperature and a pressure rise because of combustion can be observed.

I took the values of the Aprilia RSA and a more mundane 125 cc engine for comparison.
Power @13000 rpm . . . . . . . . 54 . . . . . . . . . . . .40
ignition timing bTDC . . . . . . . .14* . . . . . . . . . . .18*
ignition delay. . . . . . . . . . . . . .7* . . . . . . . . . . . .9*
combustion duration . . . . . . . 46* . . . . . . . . . . . 60*
combustion completed aTDC . .39* . . . . . . . . . . .51*



While we're on the topic of ignition timing and combustion duration, I have a question about bore size. I've seen Wobbly, and maybe others, state that a fast water cooled 125cc should have ignition timing in the range of 15* BTDC at peak if everything is near optimal. Is this peak torque OR peak power OR both?

Also, how loosely does this apply for much larger bore engines, say 80mm or larger? I assume it comes down to the combustion duration. Can combustion duration be similar in large bore engines to a 125cc? Another scenario would be going from big to bigger...going from 80mm bore to 85mm bore, the old practice would be to throw a few (+3*) timing at it to account for the 'longer burn time' from the larger bore. Does that make sense or is that old practice just masking a problem?

[Frits Overmars]

I've seen Wobbly, and maybe others, state that a fast water cooled 125cc should have ignition timing in the range of 15* BTDC at peak if everything is near optimal. Is this peak torque OR peak power OR both?Both, more or less. The RSA for example has 16˚ at max.torque (12500 rpm) and 15˚ or 14˚ at max.power (13000 rpm).


how loosely does this apply for much larger bore engines, say 80mm or larger? I assume it comes down to the combustion duration. Can combustion duration be similar in large bore engines to a 125cc? Another scenario would be going from big to bigger...going from 80mm bore to 85mm bore, the old practice would be to throw a few (+3*) timing at it to account for the 'longer burn time' from the larger bore.Combustion duration, expressed in seconds, will be longer when the bore gets bigger and the flame has to travel over a greater distance.
But as the bore gets bigger, the specific angle.areas become smaller and the revs must become lower in order to maintain the optimum specific time.areas.
Because of these lower revs, the combustion duration, expressed in crank degrees, will be largely independent on the bore. And the same goes for the ignition timing.

In reality, big singles often have a couple of degrees more ignition advance as a consequence of the fact that big singles are usually found in MX, Enduro and similar forms of agricultural racing, where combustion duration is a bit longer because the engines are not as highly tuned as the small-bore units used in road racing and karting.

[jasonu]

The Classical Performance/Development Curve. .:yes:

https://s3.amazonaws.com/WEBPOSTS/KIWI+ESE/Performance+Development.jpg

Cheers, Daryl.

How about a money spent vs gains graph...

[Pursang]

big singles are usually found in MX, Enduro and similar forms of agricultural racing, .

AGRICULTURAL RACING!:woohoo:

https://s3.amazonaws.com/WEBPOSTS/OZVMX/Cultivator/2011+RC.jpg
https://s3.amazonaws.com/WEBPOSTS/OZVMX/Cultivator/2013+RC.jpg

Cheers, Daryl.

[Flettner]

That poor little engine,

[F5 Dave]

For the love of an imaginary friend- - Why?!?!!

[Pursang]

For the love of an imaginary friend- - Why?!?!!

They Race them.... because there are More than One of them, of course!..:killingme

The Spanish village of Betxi hold a cultivator race around the village as part of their annual festival.

Machines are limited to the 'original' fitted engines and the Bultaco's are quite tuneable and popular

https://s3.amazonaws.com/WEBPOSTS/OZVMX/Cultivator/Bultaco+Cultivator.jpg

Link here: https://www.redbull.com/za-en/what-the-hell-is-the-transbetxi

Facebook page with lots of pics:https://www.facebook.com/groups/59162244965/?fref=ts

Cheers, Daryl

[jasonu]

For the love of an imaginary friend- - Why?!?!!

I dunno Dave, I think it looks like a bit of fun.

[Muciek]

On pitlane was thread about tuning them by one competitor ( cant find it right now) top speed was around 100 kmh...

[Flettner]

On pitlane was thread about tuning them by one competitor ( cant find it right now) top speed was around 100 kmh...

Thats pretty bloody good. Buggered if I would want to be on that thing at 100 Kph, race anything. :yes::2thumbsup
So long as its got a twostroke on it.

[jonny quest]

I'd like to try and make some Peek piston pin caps.

Suggestions for securing caps to piston?

No circlips, the caps snap into pistons circlip grooves. Does this sound like a good idea? Piston pin should stay secured this way, won't push caps out?

Removing caps when performing a piston change. Drill hole in cap, punch other side out?

[Frits Overmars]

Sounds strangely familiar Jonny :msn-wink:.
Kidding aside, in case you really missed what I posted about the subject, you can find some pictures (and a lot of other stuff) here:https://jmp.sh/uXqkAr9
No need to drill one of the caps in order to remove them. Just punch a tiny hole in one of 'm and apply air pressure; then the other cap will pop out, after which you can poke a screwdriver through the piston pin and push the first one out from the inside. Both caps are re-usable; the tiny hole won't matter.

[flyincat]

There's something on my mind that's constantly got me scratching my head. Spark plugs. I see over and over on various online communities (2T & 4T) with experts stating their 'opinions' on how to read a spark plug. Everyone seems to have their own variation. It usually comes down to... read the color here, measure the smoke ring there, count how many threads, etc, etc. Of course, this is usually in reference to the plugs telling you if the engine wants more or less timing, fuel, etc. This seems bass akwards to me. Shouldn't the dyno tell you what fuel and timing the engine wants? Once that is established, maybe check the plugs and make sure they aren't overheating, melting, fouling etc.? Stated another way... if we are looking at the burn mark position on the bend in the ground strap, couldn't we change the position by choosing a different heat range plug and not even touch the tune?

For example....Let's say someone brought an engine in for tuning, with completely unknown history and no spark plugs. What is the thought process to tune the engine and specify a spark plug? What specific parts of the plug are we looking at and what are we looking for?

Thanks in advance!

[karter444]

Sounds strangely familiar Jonny :msn-wink:.
Kidding aside, in case you really missed what I posted about the subject, you can find some pictures (and a lot of other stuff) here:https://jmp.sh/uXqkAr9
No need to drill one of the caps in order to remove them. Just punch a tiny hole in one of 'm and apply air pressure; then the other cap will pop out, after which you can poke a screwdriver through the piston pin and push the first one out from the inside. Both caps are re-usable; the tiny hole won't matter.

Hi Frits
do you know where you can buy piston pin plugs similar to the ones as per your photos
regards Richard

[Frits Overmars]

Nope. A friend used to make them for a while, but he is too busy expanding his empire. That is why I posted the pictures and drawings here, in the open, so everybody could give it a try themselves. They're not that difficult to make.

[Flettner]

Haha, Frits, it's a bugger being a know it all, all these questions day after day. But we thank you for your time to answer them, I'm glad some one knows the right answers.
And when you consider the whole twostroke world, we are glad you come over to our little corner. Thank You, we appreciate you.

[Frits Overmars]

Haha, Frits, it's a bugger being a know it all, all these questions day after day. But we thank you for your time to answer them, I'm glad some one knows the right answers.
And when you consider the whole twostroke world, we are glad you come over to our little corner. Thank You, we appreciate you.Thanks Neil, you made my day (night really, because it's 01:28 am over here).
What do you mean by 'our little corner'? KiwiBiker? I'll have you know that Kiwibiker and Pit-Lane are the two open forums that I appreciate the most. I really enjoy coming here.
There's a trick in knowing the right answers: start at an early age, make all the mistakes you can think of, and grow old. And I have to thank my father who let me find my own way, and Jan Thiel who shared his thoughts with me, and a lot of friends with whom I brainstorm over tea (that's emot) and stronger beverages.
I'm a happy camper :D.

[husaberg]

Thanks Neil, you made my day (night really, because it's 01:28 am over here).
What do you mean by 'our little corner'? KiwiBiker? I'll have you know that Kiwibiker and Pit-Lane are the two open forums that I appreciate the most. I really enjoy coming here.
There's a trick in knowing the right answers: start at an early age, make all the mistakes you can think of, and grow old. And I have to thank my father who let me find my own way, and Jan Thiel who shared his thoughts with me, and a lot of friends with whom I brainstorm over tea (that's emot) and stronger beverages.
I'm a happy camper :D.

Can you see if Emot are still selling the Russian insulating paint, i had a look on the website the other dauy and couldnt see it.

[Tim Ey]

Can you see if Emot are still selling the Russian insulating paint, i had a look on the website the other dauy and couldnt see it.

Funny husa, I was looking for the very same stuff two days ago :-)
But an other question, since it is possible to ceramic-coat exhaust pipes, wouldnt it be possible to do the same to the inside of a crankhousing?
My Vespa engines are getting hot as hell...

[Frits Overmars]

Can you see if Emot are still selling the Russian insulating paint, i had a look on the website the other dauy and couldnt see it.Not from where I'm sitting. I could email him, but so can you: stehouwer@emot.nl

[Tim Ey]

Sorry for the off-topic. I just found out by accident, that my favorite book "The Racing Motorcycle" by John Bradley has a third volume on the market :love:
http://www.broadlandleisure.com/
This is literally the best series of books for any racing motorcyclist with greasy hands. Written from a genius guy that brings the very best of the theory and practical experience together!
Please buy his stuff and make him rich!

[philou]

Still no reissue of volume 2 :(

[lodgernz]

Still no reissue of volume 2 :(

The publishers accidentally destroyed the plates, so no re-issue ever. He might rewrite it though. He's thinking about it but it's major of course.

[Michael Moore]

To be more accurate, the printers destroyed the plates. John has been the publisher for all three books.

Buy lots of copies of V3 so John's house isn't so crowded and maybe he can get V1&2 organized for a final reprinting.

[rtechracing]

In general widening any port trumps raising it, but widening the exhaust port will also increase the risk of short-circuiting, especially with those H2-transfers.

I don't follow your reasoning about reducing the power stroke. Raising the exhaust roof means opening the exhaust port earlier, when the cylinder pressure is higher, generating stronger pipe action.

Frits
What do you mean "especially with those H2 transfers"?
I thought 3-port exhausts and butterfly exhaust mainly had issues with short-circuiting?
Thanks

[Frits Overmars]

The Kawa 750H2 had its three 250cc cylinders crowded closely together. There was no room for nicely sweeping transfer ducts; the ducts were flat without inner curvatures, so the incoming transfer streams had hardly any directional stability; the smallest bit of suction from the exhaust side could persuade them to short-circuit.

[TZ350]

342196 342199 342198

Made some progress tonight on the CVT rotary valve GP/NSR110 engine transmission assembly with chain final drive.

342197

And this will be where we get to see if you can rely have ridiculous amounts of crankcase volume for the pipe to suck fresh fuel/mixture from.

I am picking we only need enough crankcase compression to get started and once the pipe is working it won't matter how big the crankcase volume is and the CVT will keep the engine rpm in the pipes happy place.

[husaberg]

342196 342199 342198

Made some progress tonight on the CVT GP/NSR110 engine transmission assembly.

342197

This will be where we get to see if you can rely have ridiculous amounts of crankcase volume for the pipe to suck fresh fuel/mixture from.

looking into that crankcase reminds me on a mid 50's Villiers

[Grumph]

looking into that crankcase reminds me on a mid 50's Villiers

The primary compression may even be worse. The Villiers has less crank to case side clearance - and way less transfer volume.
I did once measure the primary compression of my 197 special. Wrote it down, looked at it in relation to Gordon Jennings recommended figures, tore the piece of paper up and threw it away. It is what it is and I had to live with it.
From what wob has written about reed valves and primary compression ratios I'm reluctant to reed valve it. Making better transfers for it will increase case volume even further...

For all those reasons, I'm watching Robs efforts on this one with interest.

[husaberg]

The primary compression may even be worse. The Villiers has less crank to case side clearance - and way less transfer volume.
I did once measure the primary compression of my 197 special. Wrote it down, looked at it in relation to Gordon Jennings recommended figures, tore the piece of paper up and threw it away. It is what it is and I had to live with it.
From what wob has written about reed valves and primary compression ratios I'm reluctant to reed valve it. Making better transfers for it will increase case volume even further...

For all those reasons, I'm watching Robs efforts on this one with interest.

Yeah but the villiers still needs a decent crank, your one fixed that with also i assume full circle webs and a big end and little bearing.
plus less fins than a 1980's car
They did have tremendously long rods though. along with a huge volume under it.
For those who never had the pleasure of looking in one of these.
342200342201342202

[Grumph]

Nope - mine's still the OE crank and rod. Haven't got around to doing the DT360 conversion.
Keeping the revs lowish while getting good power out of it is fine until it reaches it's heat rejection limits - and seizes.
Next move is probably Methanol.

[lucf]

The Kawa 750H2 had its three 250cc cylinders crowded closely together. There was no room for nicely sweeping transfer ducts; the ducts were flat without inner curvatures, so the incoming transfer streams had hardly any directional stability; the smallest bit of suction from the exhaust side could persuade them to short-circuit.

Are you serious to make people believe this with that high speed of the incoming transferstream?
And the reason why not to widen the exhaustport ?

[TZ350]

I did once measure the primary compression of my 197 special. Wrote it down, looked at it in relation to Gordon Jennings recommended figures, tore the piece of paper up and threw it away. It is what it is and I had to live with it.

From what wob has written about reed valves and primary compression ratios I'm reluctant to reed valve it. Making better transfers for it will increase case volume even further...

For all those reasons, I'm watching Robs efforts on this one with interest.

Extra large crankcase volume has been done before but the CVT NSR110 will have crazy big crankcase volume.

342203342205342204

My first NSR110 cc 31 rwhp effort with its special crank, very long RD400 rod, 12mm crankcase splitter and 12mm cylinder base plate. It had a very large crankcase volume compared to others. Probably bigger than the Aprilia 125 racer or anything else that you would consider a performance two stroke engine.

But I suspect being rotary valve has a lot to do with getting away with these large case volumes and the better modern pipes than in Jennings day make good use of the extra volume.

[lodgernz]

342196 342199 342198

Made some progress tonight on the CVT rotary valve GP/NSR110 engine transmission assembly with chain final drive.

342197

And this will be where we get to see if you can rely have ridiculous amounts of crankcase volume for the pipe to suck fresh fuel/mixture from.

I am picking we only need enough crankcase compression to get started and once the pipe is working it won't matter how big the crankcase volume is and the CVT will keep the engine rpm in the pipes happy place.

Rob I understand the plate between the cases was necessary on the first 110 so you could fit a 6-speed box, but why do you need it for the CVT version?

[Frits Overmars]

Rob I understand the plate between the cases was necessary on the first 110 so you could fit a 6-speed box, but why do you need it for the CVT version?I wondered about that too. I am not so concerned about the crankcase volume, but more about the distance between the crankshaft main bearings, which will cause a large bending moment on the big end pin.

[TZ350]

Rob I understand the plate between the cases was necessary on the first 110 so you could fit a 6-speed box, but why do you need it for the CVT version?

The 12mm plate acts as the backbone. Everything mounts off it and it also forms the engine mounting points in the frame.

342208


I wondered about that too. I am not so concerned about the crankcase volume, but more about the distance between the crankshaft main bearings, which will cause a large bending moment on the big end pin.

True about the bending moment on the big end pin, but the pin will be the same as the first unit that has run successfully.

[Flettner]

The Kawa 750H2 had its three 250cc cylinders crowded closely together. There was no room for nicely sweeping transfer ducts; the ducts were flat without inner curvatures, so the incoming transfer streams had hardly any directional stability; the smallest bit of suction from the exhaust side could persuade them to short-circuit.

Wasn't just the three cylinders, seems Kawasaki preferred that type of transfer design through out. My 350 has nasty little transfer ducts, short sharp and square, probably just lucky the chamber is too shit to create a decent suction. Thought a few times about casting up a new barrel, can't be bothered, put my resources into the new engine, better spent time I believe.

[Pursang]

True about the bending moment on the big end pin, but the pin will be the same as the first unit that has run successfully.

How about machining some bearing carrier housings that press (or weld or screw) into the cases and put the bearings out by the crank webs. Will reduce case volume slightly too!

cheers, Daryl

[JanBros]

or just mill 12mm from the crankcase (6mm from each crankcase half ?), or as much as possible ?

[TZ350]

.
There will be no need. This arrangement with a slightly larger diameter pin for the RD400 rod and 12mm longer to move the crank webs further apart has worked successfully before.

342215342216

[TZ350]

342218

Not always the safest but it gets the job done.

[TZ350]

342219

Some general pictures of how the CVT is going to be mounted in the frame. All trendy with a stacked motor/gearbox configuration.

342220342221342222342223

[Pursang]

342218

Not always the safest but it gets the job done.

Way Safer than a 9" angle grinder.:msn-wink:

And its a pretty impressive job your doing.

cheers, Daryl.

[Grumph]

Not always the safest but it gets the job done.

I prefer a bandsaw. Bit more control.

I wonder sometimes if anyone at Honda is looking at what is being done with these frames. And what the reaction is...
I know Rex McCandless was quite proud that his Featherbed design took on a life of it's own with all types of engine fitted.

[Carel H]

I prefer a bandsaw. Bit more control.

I wonder sometimes if anyone at Honda is looking at what is being done with these frames. And what the reaction is...
I know Rex McCandless was quite proud that his Featherbed design took on a life of it's own with all types of engine fitted.

Went to the Assen TT with 2 of my twin spar bikes, designed with my schoolbooks. Found a bunch of Japanese under it. Had a good conversation with the mechanic of Armstrong Rotax at another race. They did it in carbon. Everybody goes independent in the same direction at the same time.

[Frits Overmars]

Went to the Assen TT with 2 of my twin spar bikes, designed with my schoolbooks. Found a bunch of Japanese under it. Had a good conversation with the mechanic of Armstrong Rotax at another race. They did it in carbon. Everybody goes independent in the same direction at the same time.Aha, it suddenly dawns on me who Carel H might be! Carel, why don't you show us some pics of your homebuilt bikes and engines?

[dtenney]

I believe somewhere on this thread here was a brief discussion about pulse jet engines. A collector in the US is auctioning off his model airplane engine and pulse jet engine collection. If anyone in interested please let me know and I will share the address. It loooks like there are about 20 pulse jet engines in the collection.

[TZ350]

Aha, it suddenly dawns on me who Carel H might be! Carel, why don't you show us some pics of your homebuilt bikes and engines?

Yes, please do, we love to see pictures of other peoples projects....... :)

[Flettner]

https://youtu.be/bhKrRlZxomc

So, what if the opening gib was controlled by the rider, and the shut side gib was controlled by the ECU. I can do that with the LINK now, A question or a statement. I'm guessing someone will have some thoughts. I'll leave it set up as it is for the moment but want some ECU throttle input eventually. Too hard to do both at the moment for LINK.
A box of interesting fuel injection stuff arrived at my back door a few days ago, thanks TZ, just the piece I was looling for😆.
New replacement ceramic tip temp sensor has turned up for the foundry so back into casting again. Mold up some cylinders this weekend.

[Carel H]

Yes, please do, we love to see pictures of other peoples projects....... :)

This is about finished projects of the past. But Ok. A recent fun photo of a magnesium casting I still have.
Sort of horizontally split single cilinder with a cassette gearbox.

The idea was to make an engine that would not explode before the finishline, in order to get normal race to race development.
The not exploding in any form target was reached, the management thing underestimated.

Thou shall be rich enough to maintain control of what's happening. I was not, I was just the designer. Racing is complex.

[Frits Overmars]

what if the opening gib was controlled by the rider, and the shut side gib was controlled by the ECU. I can do that with the LINK now, A question or a statement. I'm guessing someone will have some thoughts. I'll leave it set up as it is for the moment but want some ECU throttle input eventually. Too hard to do both at the moment for LINK.The opening gib should open as soon as the crankcase pressure has dropped below the ambient pressure, preventing the crankcase pressure from dropping too far, which would slow down or even reverse the transfer flow. So the opening gib timing mainly depends on engine rpm: the lower the revs, the earlier the opening gib should open. But I don't think controlling the engine power via the opening gib would be a good idea; the feeling would be far from linear.

The inlet flow has a natural Helmholtz frequency and the higher the revs, the more crank degrees should pass during one Helmholtz cycle. But the ECU must know the position of the opening gib in order to be able to calculate the optimum closing gib position. Only then can it take orders from the rider and close even earlier when less power is ordered.
If it is too hard to do both at the moment for LINK, I'd rather choose a fixed late-opening position for the opening gib and let the closing gib do all the work.

[Flettner]

The opening gib should open as soon as the crankcase pressure has dropped below the ambient pressure, preventing the crankcase pressure from dropping too far, which would slow down or even reverse the transfer flow. So the opening gib timing mainly depends on engine rpm: the lower the revs, the earlier the opening gib should open. But I don't think controlling the engine power via the opening gib would be a good idea; the feeling would be far from linear.

The inlet flow has a natural Helmholtz frequency and the higher the revs, the more crank degrees should pass during one Helmholtz cycle. But the ECU must know the position of the opening gib in order to be able to calculate the optimum closing gib position. Only then can it take orders from the rider and close even earlier when less power is ordered.
If it is too hard to do both at the moment for LINK, I'd rather choose a fixed late-opening position for the opening gib and let the closing gib do all the work.

Yes Frits, with the above scenario both gibs need a TPS, the ECU must know this information but will only be able to drive one of the gibs. An RPM delay mechanism on the opening gib might be necessary, although with 360cc Rotary Valve HP that just might come naturally. Self preservation.

Perhaps below a certain RPM I just don't close the gibs off, use injection frequencies only to control power. Hit and miss engine comes to mind. That might make for an interesting ride picking through fallen logs and slippery sticks. Perhaps a large flywheel would be in order. :shit:
Never the less it might make for an interesting experiment but I will get someone else to ride it for this test.

[Flettner]

This is about finished projects of the past. But Ok. A recent fun photo of a magnesium casting I still have.
Sort of horizontally split single cilinder with a cassette gearbox.

The idea was to make an engine that would not explode before the finishline, in order to get normal race to race development.
The not exploding in any form target was reached, the management thing underestimated.

Thou shall be rich enough to maintain control of what's happening. I was not, I was just the designer. Racing is complex.


Cat will sort it for you, I use mine to bounce ideas off. She is always right, bugger it. Alien data loggers. <_<

[Pursang]

The opening gib should open as soon as the crankcase pressure has dropped below the ambient pressure, preventing the crankcase pressure from dropping too far, which would slow down or even reverse the transfer flow. So the opening gib timing mainly depends on engine rpm: the lower the revs, the earlier the opening gib should open. But I don't think controlling the engine power via the opening gib would be a good idea; the feeling would be far from linear.

The inlet flow has a natural Helmholtz frequency and the higher the revs, the more crank degrees should pass during one Helmholtz cycle. But the ECU must know the position of the opening gib in order to be able to calculate the optimum closing gib position. Only then can it take orders from the rider and close even earlier when less power is ordered.
If it is too hard to do both at the moment for LINK, I'd rather choose a fixed late-opening position for the opening gib and let the closing gib do all the work.

TZ350 is measuring crankcase high and low pressures.
Perhaps the opening gib can reference these and be independently controlled to maintain optimum case pressure.

Cheers, Daryl.

[Pursang]

Yes Frits, with the above scenario both gibs need a TPS, the ECU must know this information but will only be able to drive one of the gibs. An RPM delay mechanism on the opening gib might be necessary, although with 360cc Rotary Valve HP that just might come naturally. Self preservation.

Perhaps below a certain RPM I just don't close the gibs off, use injection frequencies only to control power. Hit and miss engine comes to mind. That might make for an interesting ride picking through fallen logs and slippery sticks. Perhaps a large flywheel would be in order. :shit:
Never the less it might make for an interesting experiment but I will get someone else to ride it for this test.

Power (and airflow) follows fuel Works for Diesels. Many 4WDrivers would rather pick through (and over) rocks and logs using diesel power instead of petrol.
Don't forget to Video the Test..

Cheers, Daryl.

[husaberg]

Cat will sort it for you, I use mine to bounce ideas off. She is always right, bugger it. Alien data loggers. <_<

The cat might be a KTM spy.......

[Flettner]

The cat might be a KTM spy.......

Opps, found the mole, the cat must die. Come to think of it, she does have an Austrian accent😆.

[F5 Dave]

Ahh, cute cat photos . This is the internet after all.

Kaaden sez Meow.


. . . and don't get greedy with exhaust port timing.

[Peter1962]

Opps, found the mole, the cat must die. Come to think of it, she does have an Austrian accent😆.

Does she wear Lederhosen ?

https://i.pinimg.com/originals/cf/f5/79/cff57966eba46533da58d9d2e376a400.jpg

[Carel H]

This started with twin spar frames.

Had a good photo of the bare thing on wheels, but this gives a better structural overview.
1984, This is archeological. Found a magazine with a GP preview of the machines, not a twin spar to be found, only complex gates, as I called them. In 2-3 years twin spar was universal.

[Carel H]

Primary gears and clutch.

As the engine was a combination of a Kawasaki crankshaft (chosen for excellent results in motocross and the only 80cc then with a reasonable bore/stroke ratio) and a Suzuki gearbox (nice spaced race ratios) the primary transmission was not off the shelf.

Also considering the wall between gearbox and crankcase was thicker because of waterchannels for cooling purposes, increasing the distance between gearbox and crankcase. Side advantage is that the rotary disc diameter is less limited by the gearbox bearing or gears.

The gears were made by Dick de Jager, Holland. A master in this field.

He made them with heightened pitchcircle, giving a stronger toothbase. And he honed the bore of the clutch gear to near zero clearance, which given the fact that this a single needle bearing, took away that "loose" feeling that other clutches have.

As this was to be a dry clutch, instead of the original, I made bronze frictionplates.

But to our astonishment, the whole Suzuki set, plain aluminium and aluminium frictionplates were just as happy outside.

As this is the internet, I'll keep the chief engineers around for a while.

[Frits Overmars]

Meet the team:
342255 342254

[philou]

Just finish checking port chamfers

342268

[Flettner]

Meet the team:
342255 342254
expensive cat feeder.

[F5 Dave]

I don't see 30,000 rpm in here!

[Carel H]

Pistons I made from Mahle forgings. You need a few special homemade tools to make them, but making them in house gives the freedom to optimize or change everything, be it shape or size. Piston rings were Kawasaki. Turned with diamond!

[Grumph]

I've posted this before - but hey, why not again....

[andreas]

Just put this Husq/Cagiva cr 250 in my RD junior frame. It's such a nifty engine.

[Flettner]

Just put this Husq/Cagiva cr 250 in my RD junior frame. It's such a nifty engine.
Where is your cat picture?😆

[andreas]

Where is your cat picture?😆

Yes, how inconsiderate. I'll do better.

[Grumph]

Where is your cat picture?��

Sorry Andreas but I thought the motor and bits looked a bit ratty...

[Peter1962]

Not related to buckets, nor road racing in general but nevertheless important news for the future of two stroke racing : the UK sanctioning body just decided that in 2020 their national championship 250cc motocross will be opened for two stroke bikes ! :yes:

It will be interesting, to see competition at top level between 250cc four strokes and 250cc two strokes. Finally...

[andreas]

Sorry Andreas but I thought the motor and bits looked a bit ratty...
100 euro for it, besides it matches the rest neatly.Could use a new W?ssner of course.

[Grumph]

100 euro for it, besides it matches the rest neatly.Could use a new W?ssner of course.

Good buying. You're seeing the benefits of a bigger population base. We don't see that sort of engine for that price here.

[lodgernz]

Not related to buckets, nor road racing in general but nevertheless important news for the future of two stroke racing : the UK sanctioning body just decided that in 2020 their national championship 250cc motocross will be opened for two stroke bikes ! :yes:

It will be interesting, to see competition at top level between 250cc four strokes and 250cc two strokes. Finally...

Are sure they will allow 250 2-strokes? I'd be very surprised if they don't have some massive capacity penalty.

[Frits Overmars]

the UK sanctioning body just decided that in 2020 their national championship 250cc motocross will be opened for two stroke bikes ! :yes:.
It will be interesting, to see competition at top level between 250cc four strokes and 250cc two strokes. Finally...
Are sure they will allow 250 2-strokes? I'd be very surprised if they don't have some massive capacity penalty.My thoughts too. Either that, or the 250cc foulstrokes will suffer a massive built-in power penalty :D.

[husaberg]

My thoughts too. Either that, or the 250cc foulstrokes will suffer a massive built-in power penalty :D.

Years ago the AMA allowed the 250 2s to run with the 250 4ts in non experts and vets
pretty sure NZ MNZ also allows the 250 2ts to run with the 250 4ts for one class anyway.
its likey been 10 years since a real new 250MX bike was made.

[Peter1962]

Are sure they will allow 250 2-strokes? I'd be very surprised if they don't have some massive capacity penalty.

This seems to be serious :


The Maxxis ACU British Motocross Championship will lift the restriction on 250cc two-Strokes competing in the Maxxis MX2 class from 2020 onwards. The new rule will allow 120cc to 250cc for two-stroke engines and 175cc to 250cc four-stroke engines. The ACU Motocross Committee feels that with the increased costs of four-stroke machines it is imperative to keep the sport affordable for all. ACU Motocross Chairman and Maxxis Championship Race Director Steve McCauley said ?We feel the time is right to allow this?into the main British Championship. We firmly believe that we must try new ideas and progress the sport wherever possible we also believe that by making and announcing our decisions a long time in advance it gives everyone fair notice to plan accordingly.?

source : https://motocrossactionmag.com/whats-gonna-happen-in-the-next-24-hours-get-ready-for-it/

from the official website of the british championship :


From next season 250cc two-strokes will be eligible for the MX2 class of the Maxxis ACU British Motocross Championship supported by Pro Clean.

The rule change follows a landmark decision by the ACU Motocross Committee after a positive meeting with team managers at the Blaxhall round of the championship earlier this month.

The ACU has allowed 250 two-strokes to race in the MX2 class since 2018 with the exception of the Maxxis championship and the new ruling brings Britain?s main domestic series into line with many other countries including Holland, Canada and Australia.

Verde Substance KTM?s Brad Anderson, a two-time EMX300 champion who is currently contesting the Maxxis MX1 class on a 250cc two-stroke, welcomed the decision.

?It?s good news for all two-stroke riders,? he said, ?and I think you?ll get a lot more riders lining up. There?s definitely no advantage being on a 250 two-stroke against a 250 four-stroke ? when the four-strokes are tuned they?re powerful bikes. Maybe some tracks will suit a two-stroke more but on other tracks it will be better to be on a four-stroke

source : http://www.mxgb.co.uk/article.php?id=1139

[Peter1962]

Years ago the AMA allowed the 250 2s to run with the 250 4ts in non experts and vets
pretty sure NZ MNZ also allows the 250 2ts to run with the 250 4ts for one class anyway.
its likey been 10 years since a real new 250MX bike was made.

KTM made a completely new engine in 2017, the first with a balancer. This engine is (in its enduro version) now totally dominating the enduro championships.
Look for instance at the latest entrylist of the famous Erzberg Enduro : more than 90% are two stroke engines. And a large part of those are KTM or husqvarna (same bike, different colours)

This prompted TM to rework their 250 engine, now they have also an internal balancer, plus a very compact electric starter. They also have an electronic powervalve.

But on the japanese front : nada... The yamaha 250yz is a 2006 engine. Suzuki, kawasaki and honda have nothing.

[DoldGuy]

KTM made a completely new engine in 2017, the first with a balancer. This engine is (in its enduro version) now totally dominating the enduro championships.
Look for instance at the latest entrylist of the famous Erzberg Enduro : more than 90% are two stroke engines. And a large part of those are KTM or husqvarna (same bike, different colours)

This prompted TM to rework their 250 engine, now they have also an internal balancer, plus a very compact electric starter. They also have an electronic powervalve.

But on the japanese front : nada... The yamaha 250yz is a 2006 engine. Suzuki, kawasaki and honda have nothing.

As much as I love the 2 strokes, I have to disagree they are at an advantage over the current 250 foulstrokes as they (MX Motors) are almost making the same peak power as the 2 strokes but with WAY MORE range. If you also compare the lap times (again MX) the 250?s are very close to the 450?s which will currently kill a 250 two stroke in range and peak power. If they are allowed it should be MUCH more cost effective and hopefully bring in new/more participants.

The extreme enduros are totally dominated by 2 strokes, and as of late, many more manufacturers with competitive bikes, Gas-Gas/Sherco/Beta...

[Flettner]

As much as I love the 2 strokes, I have to disagree they are at an advantage over the current 250 foulstrokes as they (MX Motors) are almost making the same peak power as the 2 strokes but with WAY MORE range. If you also compare the lap times (again MX) the 250?s are very close to the 450?s which will currently kill a 250 two stroke in range and peak power. If they are allowed it should be MUCH more cost effective and hopefully bring in new/more participants.

The extreme enduros are totally dominated by 2 strokes, and as of late, many more manufacturers with competitive bikes, Gas-Gas/Sherco/Beta...

Agree, trouble is there has been no real development of the twostroke ( short of TPI ) in the last 10 years. Jolly fourstrokes have the advantage of as you say wide power spread AND superior hook up. A modern twostroke using sliding gib rotary valve plus the advantage of TPI manipulation will have way more peak power, way wide torque curve and hook up that can out perform a fourstroke. Whats stopping the manufacturers? No one wants twostrokes anymore. Stick with 4T until electric makes its way to the top of the heap. This preasant situation is ripe for a good old fourstroke ass kicking by a twostroke of most modern design, but it will have to be funded private. Even TM are not forward thinking enough.
I've designed my 360 mk2 TPI so it can be dropped to 250, same stroke, brings the bore and stroke more or less square. I'm not suggesting I could build an MX winning bike but I think we could do a lot better than whats available at the moment.

[koenich]

2017 EMX250 rules also allowed 250 4strokes vs 250 2 strokes - but as already mentioned with the currently available 2strokes I absolutely agree that a 4stroke is a major advantage. Range, throttle response/controllability and much easier to ride (read less tiring). If I remember well there weren't even many starters on a 2stroke.

I own a YZ250 and recently had a chance to try a YZ-F250 on the same day and track, it's scary how much easier a 4stroke is to ride :confused:

Enduro is another animal but I'm sure in terms of rideability a 4stroke would be at advantage - but spilling coolant in the first slow section...

[Flettner]

2017 EMX250 rules also allowed 250 4strokes vs 250 2 strokes - but as already mentioned with the currently available 2strokes I absolutely agree that a 4stroke is a major advantage. Range, throttle response/controllability and much easier to ride (read less tiring). If I remember well there weren't even many starters on a 2stroke.

I own a YZ250 and recently had a chance to try a YZ-F250 on the same day and track, it's scary how much easier a 4stroke is to ride :confused:

Enduro is another animal but I'm sure in terms of rideability a 4stroke would be at advantage - but spilling coolant in the first slow section...

I know what you are talking about, I had a 250F and rode it a while. Gutless but fast, and easy to ride compared to my 2T YZ. (but not as much fun).
Sold the engine out of it, that fixed it. Its the frame the 360 MK2 TPI is in now. I would like this 360 to be just as 'rideable' as the 250F was only a shit load more power. With the use of electronic control.

[ken seeber]

250 2 strokes against the 250 4 strokes.....fantastic.
We're the underdogs.....
Now, all we have to do is to beat the bastards...:first:

[Carel H]

Finished crankcase, finished as of 35 years ago.

Casting was necessary for the flanged chamber of the gearbox. I kept the casting as simple (or industrial) as possible. Better mill a bit than having nothing at all. Most of the retainers for the bearings are separate parts, the crankcase bearings with rings in grooves.

This is how I wanted it, ball and roller bearing for the crankshaft in a horizontally split case. There were a lot of crankshaft bearing religions where I was not a follower off.

Visible is the tilted split for the crankshaft, with 2 nuts above the cilinder base and 2 in pockets on the underside.

[Tim Ey]

250 2 strokes against the 250 4 strokes.....fantastic.
We're the underdogs.....
Now, all we have to do is to beat the bastards...:first:

That might actually be more of a challenge than you might think.

[husaberg]

That might actually be more of a challenge than you might think.

I have heard of friendly dynos but i suspect that one would be humping as well as pulling your leg.
that is where i have seen most 450's sit.
here is a dynojet on a CRF450
Dynojets are are know to be friendly

https://www.youtube.com/watch?v=3yvZ2wyHCy8
to put this into perspective how little they have evolved my 19 year old Husaberg puts out 50HP at the rear wheel from 50cc more.

[Flettner]

This is my F9 Kawasaki rear wheel HP. Not ideal bore and stroke, 80 x 70, shitty hacked up FMF pipe, untouched 1973 transfers, just barrel raised, air cooled (and ethanol) with some exhaust port widening it would have to be close to 45 RW HP now. No power valve. This engine has never been optimized in any way just seat of the pants tuning (and a bit of a stint on Robs dyno early on)

It would make sense that a water cooled 250cc version with a much more modern cylinder with proper ports, chamber made by someone that knows what they are doing, exhaust power valve and the same sliding Gib valve housing should rev harder, produce similar bottom end and have way more mid range power. In a decent frame?

Add state of the art TPI (the new version, much better homogenization ) the sliding open and close Gib, perhaps even dual rotary valves, I'd be surprised if it didn't give the 450's a hurry up.

Or am I just stuck on planet twostroke? (deluded)

[ken seeber]

PART 2. Sorry, but PART 1 is under Foundry...my stuff up.


?So, it?s now off to see Henri Tiben (another national champion). Bit out of the way, just only 800 met from the German border.? Henri is a Freetech 50 man, his current bike running a Bidalot cylinder with a side mounted rotary disc valve.

342338342339342340

In the best interests of a positive relationship between northern and southern hemisphere 2 stroke types, the southerners offered some simple 2 stroke tuning tips, which I?m sure will give a 2 hp increase over the 22 hp of a 50 cc bike. Obviously I?d love to tell you more, but we?ll have to wait until the patents are fully cleared.

Overall it was really great, so many thanks to Frits, Martijn and Henri for the day. And the giggle of the day was:

342341

[Peter1962]

This is my F9 Kawasaki rear wheel HP. Not ideal bore and stroke, 80 x 70, shitty hacked up FMF pipe, untouched 1973 transfers, just barrel raised, air cooled (and ethanol) with some exhaust port widening it would have to be close to 45 RW HP now. No power valve. This engine has never been optimized in any way just seat of the pants tuning (and a bit of a stint on Robs dyno early on)

It would make sense that a water cooled 250cc version with a much more modern cylinder with proper ports, chamber made by someone that knows what they are doing, exhaust power valve and the same sliding Gib valve housing should rev harder, produce similar bottom end and have way more mid range power. In a decent frame?

Add state of the art TPI (the new version, much better homogenization ) the sliding open and close Gib, perhaps even dual rotary valves, I'd be surprised if it didn't give the 450's a hurry up.

Or am I just stuck on planet twostroke? (deluded)


A nice cocktail would be a KTM or TM 250 model 2019 (so with balancer) and then the fun can start : I would take my Mastercard and order :
-a rear mounted, detacheble rotary valve, toothet belt driven and made out of the best aluminium, and a layer of bronze to protect the valve from excessive wear. The intake flange should be able to be used with the carburator (SX) or for the enduro version the injection body. (interchangeable)
-the sliding double gib system made by Fletner is an absolute must.
-surface treatment of the gearbox, crank and rod as described here on Ese's thread, but can not recal the name of the kiwi company... :(
-forced lubrication of the big end, suzuki GT750 style, or a more modern oilpump from a rotax E-Tec engine.
-Fabio's PowerCDI module for ignition, and since his system can take care of 2 additional features, it would command the sliding gib system
-The TM already has an electronic powervalve, to be coupled to the PowerCDI
-For KTM : ditch the actual mechanical system, and mount the new 2019TM electronic powervalve system without cables, to be coupled to the Power CDI
-SX : a 38 Smartcarb model 2 with TPS, as an alternative for a Keihin 38 with TPS and electronic powerjet. Of course the standard mikuni goes to the clicker
-Enduro : the TPI system that comes standard with KTM, or the new TM system, but coupled to Power CDI
-the exhaust : full analysis in Engmod by Master Jedi Wobly, to be ordered in double because of the rather clumsy riding habbits of me-myself, coupled to the infamous Law of Murphy that prescribes that the beautiful exhaust will be ruined after just one ride. And ordering a new exhaust in New Zealand, to Belgium, should probably take more than 24 hours. :facepalm:
-on the Enduro model (so, with TPI) : order a sticker : 'thank you Fletner' and apply to both sides of the bike in the most visuable place just to annoy KTM
-AS3 Performance : oversized water pump impeller

Next fase : explain to the missus where all the money has been spent...

BUT : destroy the lads who come to the local trac with their honda crf 450 farming equipment. :2thumbsup

[Flettner]

All we have to do is just make it happen.

I'm quite keen on this 175 engine I've got lined up next. Same tech but a new piston design so I can have exhaust ports right around to half way. Bridged exhaust but both ports leading to two separate outlets (back to the future, CZ) get as much blow down time area as possible and best exit flow for the exhaust gasses. Easy to run the water right up to the bridge as well. Still side RV, convenience, probably put a balance shaft in it, use that to turn the crank backwards, like my 360. Reverse pipes like the 360 for pipe safety and heat retention with river crossings etc.

It seems harder to get stuff done these days, easy to talk. In saying that I should get the last shafts off to get hardened for the 360's kick start system today. After this its just the wiring. :eek5:

[Flettner]

I have spent a lot of time getting a reliable / repeatable home foundry up and running for such projects. As I've said on the foundry forum, I don't mind pouring other peoples bucket projects if they arrive on my foundry floor. I will advise on pattern making but won't be doing any for other people myself. Sand mold making can be done here also but material cost will have to be covered.

I'm expecting a flood of twostroke cylinder casting:yes:

[TZ350]

<iframe width="560" height="315" src="https://www.youtube.com/embed/Cpy4cJzTqr8" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen=""></iframe>

Ok..... so its boats and dirty four stroke V8's but you have to be dead if your not impressed by the effort and results, over 200 MPH.

[DoldGuy]

I have spent a lot of time getting a reliable / repeatable home foundry up and running for such projects. As I've said on the foundry forum, I don't mind pouring other peoples bucket projects if they arrive on my foundry floor. I will advise on pattern making but won't be doing any for other people myself. Sand mold making can be done here also but material cost will have to be covered.

I'm expecting a flood of twostroke cylinder casting:yes:

And this has drawn my admiration of your “Get it done Attitude”. Your willingness to pursue, what many of us only dream of, keeps me excited to see what you have next!

[Frits Overmars]

PART 2. Sorry, but PART 1 is under Foundry...my stuff up.... Overall it was really great, so many thanks to Frits, Martijn and Henri for the day. And the giggle of the day was:342341Ken, your pictures in PART 1 work fine, but I can't open any pictures in PART 2. All I get is "Invalid Attachment specified".

[ken seeber]

Ken, your pictures in PART 1 work fine, but I can't open any pictures in PART 2. All I get is "Invalid Attachment specified".

Frits, you're right. Can't explain that one, but did experience a lot of troubles with the server I was on. Here they are:

342364342365342366342367

[wobbly]

Just cant help yourself can you Luc
.It may come as a surprise to you but this forum was not specifically designed for you to post shit about how
fucking clever you are - or even were back in 2012.
If you posted what the designs actually were or how they were derived , we would all be happy to learn something useful.
But no , we just get the same self promotional shit that got you banned in the first place.
Go away.

[TZ350]

.
Lucf has re registered as Luc


Luc if you posted what the designs actually were or how they were derived , we would all be happy to learn something useful.

Yes, I to would love to read and learn something of Luc's tuning incites.

Like all good dinner parties, its the sharing that makes things great.

342370

Luc we would love you to join the party and share your knowledge. This is a safe place where you could let your work speak for itself.

[SwePatrick]

I think he's planning to use a "retained" ring, i.e. reverse Dykes, so port width shouln't be a problem, nor should exhaust-to-transfer leakage as there would be no pin holes.

I honestly think the problem will still be there, the ring need some movement in piston 'radially' this can cause havoc when piston is 'rocking' around bottom dead centre.
Maybe a little bit less problem yes, but it will autochamfer the exhaustport quite quickly :(

[SwePatrick]

Quick question guys, i have searched but no luck.

The ralation between stiff reedpetals and crankcase volume.

Bigger volume - needs stiffer blades?

Or is it the other way around.

Rgds
Patrick

[wobbly]

Bigger case requires softer petals.
Its diminishing returns theory , the positive effects of having a bigger case get slowly erroded away by the fact that
the soft petals loose control and flutter with uncontrolled modes in the mid range.
A big case and soft petals work well at very high rpm , but in this case as you go bigger or softer the mid power gets Much worse.

[SwePatrick]

Thanks Wob.

I have actually made the case smaller this year as i had HUGE volume before, never measured, but now i have 1.3-1
I was lacking some midrange grunt before, that?s why i changed the volume.

So i?ll have to use stiffer ones now, thanks again. :yes:

[wobbly]

1.3 seems to be the approx limit.
But in any case , I have found that the best power comes from soft main petals and adding backups to control the modal flutter.
Here are some recent tests on making the mains softer , and using different backups top and bottom

[TZ350]

A big case and soft petals work well at very high rpm , but in this case as you go bigger or softer the mid power gets Much worse.

EngMod indicates a definite difference for reed and rotary valve case volumes.

It will be interesting to see if my "rotary valve" engine with its very big case volume will show a performance advantage that couldn't be realized if it was a reed valve inlet.

[Flettner]

So remind me the reason twin Rotary Valve is not a good idea? Or was it and just not tried much in practice. Was it Exact Weld (?) had a twin RV system?
Or are we best to just have a 'sliding door' that changes the crank case volume from a little bit to a lot as the pipe does its job.

[husaberg]

So remind me the reason twin Rotary Valve is not a good idea? Or was it and just not tried much in practice. Was it Exact Weld (?) had a twin RV system?
Or are we best to just have a 'sliding door' that changes the crank case volume from a little bit to a lot as the pipe does its job.

Jan said it wanted to try it and a dutch crowd made some very nice CNC crankcases to try it.
But i think the money ran out.
342378342379342380


The first RSA engine was made at Derbi, it was meant to be able to beat Aprilia.
The Derbi reed valve engine gave 47,5HP when I arrived there in 2004.
So obviously something new had to be made.
But it was improved to 49.5HP, mainly through better inlet flow and better crankcase cooling.
It's electric water pump proved insufficient, so it was not used on the RSA.

The 250RSA had side inlet, so it used RSW cylinders, all tested and developed on a 125 RSW single.
It simply was a normal 250 with the gearbox output shaft in a higher position, and therefore the crankshaft rotation had to be reversed.

The 125 RSA/Derbi was a completely different engine, with the inlet valve on the rear.
This was done after flow bench tests showed that the RSW inlet flow was very much disturbed by the connecting rod, it seemed logical at the time!
Later we realized that the RSA inlet flow collided with the cylinder wall at the opposite side.
So there was very little gain....
Fins directing the inlet flow versus the transfer tunnels would have helped I now think!

In 2006 a special RSA cylinder was made with the cylinder bolts in a different position.
It had also better cooling of the exhaust duct and small cooling canals through the inside wall of the
transfer ducts, which improved power by 0,5HP!

So I finally came upon the idea of using a disc valve on each side, as already had been done by Exactweld.
But I decided to retire, a Dutch friend made some crankcases, but never finished the work.
So I still wonder how it would have gone....

The 70HP I mentioned for the 500 was, of course, on a single cylinder.
The engine used for those tests was a 500 engine, with only 1 crankshaft fitted.
Testing on 2 cylinders is more complicated and inconvenient.

Derbi was owned by the Piaggio group, which owns several Italian makes.
At the beginning of 2005 Piaggio bought Aprilia.
So they decided to close the Derbi racing workshop and I had to return to Aprilia, which I did in 2006.

The piston melting with a bigger than 39mm carburetor was probably caused by a weak spot just before maximum torque.
Because no powerjet was used at the time....




I first tried it on a 50 cc in 1074: more power.
Going from 80 to 85
Then at Aprilia in 1996: more power.
Without varying the crankcase volume.
We went from 112 to 113 and 115, later 118 was tried, still better.
For the RSA we had to lengthen the connecting rod from 115 to 120 to improve inlet flow: more power.
It is mainly due to piston friction I think.
NSU already found this in 1953, piston friction was the main source of friction in their 250 4-stroke engine.
It may be different for a reed valve engine, I have not much experience with these.
But the piston friction loss will, of course, be the same in a reed valve engine.

Of course at BDC there is no difference as you have to adjust the cylinder height!
Maybe it is interesting that with a longer connecting rod I could use higher transfer ports on my 50.
Getting still more power!

The crankcase volume also changes, of course, unless you change the position of the piston pin in the piston, as we did at Aprilia
This can be better or worse....
You can change your crankcase volume in many ways.
But always keep in mind that flow is more important than volume.....
On rotary valve engines I found the bigger the better, within reason of course....
The Aprilia engines had very narrow crank wheels, (16mm) so a very big crankcase volume. About 660cc in TDC
A big crankcase volume makes very long inlet timings necessary.
And big carburetors.

This is probably the reason why reed-valve engines need a smaller crankcase volume.
The reeds 'decide' for themselves when to open...
They need some depression.
And because maximum inlet flow is probably determined by the reed block, big carburetors won't work on a reed-valve engine.
They just slow down the flow in the carburetor, making for a difficult carburetor adjustment.

So I think that a rotary valve engine will always give about 3-4 HP more (125cc) than a reed valve engine.
Because of its unrestricted inlet flow and less pumping losses.

[Flettner]

Thank you Glen. All I need to know.

[husaberg]

Thank you Glen. All I need to know.

If you talk to Frits he might be able to tell you if there is amny of thoose cases still about or if the file still exists seeing you have the CNC
those molds you have can make a cylinder suitable for testing.

[SwePatrick]

1.3 seems to be the approx limit.
But in any case , I have found that the best power comes from soft main petals and adding backups to control the modal flutter.
Here are some recent tests on making the mains softer , and using different backups top and bottom

Yes, i'm using 'backups' to finetune the blades, it was late yesterday after a full day of headscratching of where my power was(dynoday)
I'll try to stiffen it up today to see if it?s the answer.
I'm missing the last 500-600rpm, pipe is tuned for 13200, but now i stuck at 12600.
It has produced 69hp at 13200rpm with this pipe before, and now 56hp at 12600.
I recon i won't gain all back to 69hp, but 63-65hp might happen if it could rev past 12600 and produce power all the way, but with more torque than before due to better crankcase.

[husaberg]

Yes, i'm using 'backups' to finetune the blades, it was late yesterday after a full day of headscratching of where my power was(dynoday)
I'll try to stiffen it up today to see if it?s the answer.
I'm missing the last 500-600rpm, pipe is tuned for 13200, but now i stuck at 12600.
It has produced 69hp at 13200rpm with this pipe before, and now 56hp at 12600.
I recon i won't gain all back to 69hp, but 63-65hp might happen if it could rev past 12600 and produce power all the way, but with more torque than before due to better crankcase.

I am confused, Hp is the rate of work, ie calculated torque with the RPM.
so how if could it rev the same producing less HP, yet have more torque?

[Flettner]

Glen, nah, no need for a solid model for the CNC, I'll just make one on the pattern bench. I have a set of 175 cases cast up but with no balance shaft provision. Or provision for s second rotary valve case on the other side. And the gearbox I've modelled it around might be on the light side.
Back to the old whats best for a gearbox. Must have wide even gear spacing (WR) , robust (not Honda), cheap and readily available.
I'd just about choose a 350 Kawasaki gearbox, I have a few, they just don't break, but there change mechanism is a bit Heath and Robinson. So perhaps not.
Suzuki ? Were their gearboxes any good? Can't really go to the wreakers any more and sift through the bins, like the old days.

[Flettner]

There is something you don't see every day, a motorcycle engine based around an O200 Rolls Royce aircraft engine cylinder.
Down at my storage cow shed, looking for something else and I tripped over this. Built this when I was an apprentice at AHI plastic products. Made the patterns from Kauri from my old school that was pulled down. Managed to pilpher some four by twos before they torched the heap.
My first foray into casting, lawnmower flywheel, CB 750 gearbox, an old one at that, made the camshaft myself. As per usual I never finished it, supercharged Honda 100 got in the way, then uniflow and so on.

Don't ask why, To be old and wise, first you must be young and stupid, I guess half of that came true.

[husaberg]

There is something you don't see every day, a motorcycle engine based around an O200 Rolls Royce aircraft engine cylinder.
Down at my storage cow shed, looking for something else and I tripped over this. Built this when I was an apprentice at AHI plastic products. Made the patterns from Kauri from my old school that was pulled down. Managed to pilpher some four by twos before they torched the heap.
My first foray into casting, lawnmower flywheel, CB 750 gearbox, an old one at that, made the camshaft myself. As per usual I never finished it, supercharged Honda 100 got in the way, then uniflow and so on.

Don't ask why, To be old and wise, first you must be young and stupid.

AHI i remember the milking plants and the cup removers especially.
there is still a few around.
They later became Waikato? with another name in between?

casting look pretty sophisticated with the webs under the cam tubes. and under cylinder. plus around the bearings.
looks like you stacked the gearbox as well to keep it short?

[Flettner]

Arh, now we see, you are here touting for work, Luc.

[Flettner]

AHI i remember the milking plants and the cup removers especially.
there is still a few around.
They later became Waikato? with another name in between?

Guilty.....
Remember the plastic sandals, us too.

[husaberg]

Guilty.....
Remember the plastic sandals, us too.

Might have been Carter holt then waikato or alflex thown in.
bloody interesting history with AHI,i thought you worked for DRI or one of the predecessors.
https://www.office2u.co.nz/news/2/AHI-Alex-Harvey-Industry-Limited-History.

[Flettner]

Machined the connecting rod out of a solid piece of AHT28. That took a while but came out beautiful in the end, spent hours polishing it. Pressed up crank.
Cases were cast out of old Austin A40 differential heads, nothing but the best.

Back in the day, AHI ( then carter holt Harvey) had a monopoly so almost everything plastic was made by us.
Lawnmower catchers
telephones
All manner of plastic bottles
200 L drums, drums of all sizes.
milking equipment
Everything, it was a good place to do an apprenticeship, with a very well equipped tool room and some clever cookies.

[Haufen]

Thanks TZ, for your invitation, but the Kiwi history here is by far not friendly enough to do so.


Well Luc, the thing on this site is: no one will prepare a red carpet for you if you just keep on bragging and screaming for attention.

There are people on this site with more experience, more race wins, more drag racing championships, higher specific performances, more precise calculations, better cylinder head designs and whatever else than you. And this is with leaving Jan, Wobbly and Frits aside.

But does it matter? Do people even know? Do they care? Does anybody care? No.

They come here for the joy and the passion, to help others, exchange views and also lean something new from time to time. If you are looking for fanboys you might be better off enlisting in one of those singstar tv shows on national television. If you would like to become a valuable member of this board, you are overdue to start sharing some precise, detailed, proven and - of course - free information to earn some credit.

[TZ350]

If you would like to become a valuable member of this board, start sharing some precise, detailed, proven and - of course - free information to earn some credit.

Bringing something to the table for all to enjoy is certainly the way to participate here.

[Haufen]

Bringing something to the table for all to enjoy is certainly the way to participate here.

I am sure Luc has lots he could bring to the table. But he has not done it here so far. And it looks like he has gotten off on the wrong foot with almost everybody in here. And from his post it seemed to me that he expects people to kind of bow down before being worthy of being preached the holy two-stroke grail. Both these last things may or may not happen, what I meant to say was that the order should be the other way round.

[SwePatrick]

I am confused, Hp is the rate of work, ie calculated torque with the RPM.
so how if could it rev the same producing less HP, yet have more torque?

Not more torque in peak number, but more torque as in wider band. ;)

[SwePatrick]

I thought i'd share with you, the funniest looking dynograph ever.

342383

You get a hint if looking at the filename.
Yes, it seized today. *lol*
Big end bearing went out for lunch.
But no worries, i've got spare rod,pin and bearing ;)

[Haufen]

I thought i'd share with you, the funniest looking dynograph ever.

Could it be that your clutch started slipping at around 55 hp? Or has the shape of the power curve always been like this?

[SwePatrick]

No, it actually seized during that pull, the flat top shows the engine was about to seize.
It suddenly had a lot more resistance to turn over, a lot more friction, it ate the power and made the flat top.
Peak power is at about 12600-12800 otherwise.

[TZ350]

.

Speedpro told me he got an extra 2hp when he fitted a good central sparkplug head to his Suzuki TF-NSR125 special.

342384

Today we binned the NSR head (blue line) and fitted a VHM central plug head (purple line) and got an extra 2 hp everywhere. Shows what can be done with a good combustion chamber shape.

[F5 Dave]

Despite the peak revs being 500-700 rpm lower. Nice.

[TZ350]

Despite the peak revs being 500-700 rpm lower. Nice.

Yes, no other changes so not sure why that is .......... :scratch:

[husaberg]

Glen, nah, no need for a solid model for the CNC, I'll just make one on the pattern bench. I have a set of 175 cases cast up but with no balance shaft provision. Or provision for s second rotary valve case on the other side. And the gearbox I've modelled it around might be on the light side.
Back to the old whats best for a gearbox. Must have wide even gear spacing (WR) , robust (not Honda), cheap and readily available.
I'd just about choose a 350 Kawasaki gearbox, I have a few, they just don't break, but there change mechanism is a bit Heath and Robinson. So perhaps not.
Suzuki ? Were their gearboxes any good? Can't really go to the wreakers any more and sift through the bins, like the old days.

Use a Vt250 gearbox nice ratios strong gears quite narrow, millions made available from any wrecker in any country. nice clutch, available in 5 or 6 speeds as well. also the same gearbox is used on the MVX250 an fthe CBR250
they have an intersting gearshift set up though almost planetary. available either push or pull left or right clutch.

342385342386

[wobbly]

More com or higher msv , both do exactly as the graph shows.

[diesel pig]

Wobbly I was looking at the Superfinishing farsebook page and saw a picture of you and Dennis Charlett's 400. I was wondering wither you had the crankshaft done as well as the gearbox? I was thinking not just from the reduced friction point of view but also the improved surface providing a better seal for the crankseals and longer seal life?

[F5 Dave]

You'd think that the oil film would do that and not care too much for the details beyond smooth enough to keep a film without poking through. Maybe.

And how the hell are you?

[Pursang]

More com or higher msv , both do exactly as the graph shows.

If comp or squish haven't been changed, could the central plug create a faster & more efficient burn, and be producing higher pressure quicker.
Perhaps retarding the ignition could be tried, not for pipe heating, but to reduce the higher pressure occurring before TDC.

cheers, Daryl

[wobbly]

Denis's 400 had all of the gears done , and that included the primary gear seal surface.
I didnt do the crank as it has Peek coated washers and all the bearings are MicroBlue polished and coated.
Done before the Stealth coating was introduced in NZ.

[TZ350]

More com or higher msv , both do exactly as the graph shows.

That must be it.


If comp or squish haven't been changed, could the central plug create a faster & more efficient burn, and be producing higher pressure quicker.

342391 342409 342410

The plug in the original NSR head was offset to one side and very masked. It was a lot of compromises to get the NSR head to fit the short stroke motor. VHM's blank replaceable head inserts were a lot easier to work with. If I wasn't lazy it would have probably been easy enough to make inserts for the NSR head.

Instead of buying an expensive VHM setup if you have the skills, converting a NSR head can give just as good results too.

342392 342393 342394

[Vannik]

TZ that seems a very difficult way - we take a top head, cut off the outlet, weld the hole closed and add the inlet to the side.

[SwePatrick]

I'm searching for a piston with certain dimensions and i figure i search in your knowledge too, it might speed up my process a lot ;)

Demands:

Diam 66.5-67mm
1x piston ring with retainer pin 6 O'clock
18mm wristpin

Compressionheight isn't that very important, but around 38mm would be nice.

Rgds
Patrick

[Flettner]

plugged the LINK in tonight to have a little look at the new (to me) software.

[TZ350]

I'm searching for a piston with certain dimensions.
Diam 66.5-67mm
1x piston ring with retainer pin 6 O'clock
18mm wristpin


342402 https://www.unimotors.ro/Kit-piston-Suzuki-RM250-86-6694-6894mm-Wossner_p_68103.html

Take a look at a 1986 Suzuki RM250. 67mm std plus over sizes. 18mm pin, and maybe 6 o'clock ring peg.

[husaberg]

I'm searching for a piston with certain dimensions and i figure i search in your knowledge too, it might speed up my process a lot ;)

Demands:

Diam 66.5-67mm
1x piston ring with retainer pin 6 O'clock
18mm wristpin

Compressionheight isn't that very important, but around 38mm would be nice.

Rgds
Patrick

http://www.mitaka.co.uk/CATALOGUE/PISTON_DIMS_ALL.htm
http://www.tkrj.co.jp/
https://www.pro-x.com/wp-content/uploads/2019/02/TECHNICAL-2019_Online.pdf
http://www.pvlsverige.se/vrm/index/index22.html
http://www.mingyang-group.2u.com.tw/pdf/CAPT-Motorcycle.pdf
http://www.na.vertexpistons.com/ProductInfo.aspx?cat_details_id=31

[ranasada]

I'm searching for a piston with certain dimensions and i figure i search in your knowledge too, it might speed up my process a lot ;)

Demands:

Diam 66.5-67mm
1x piston ring with retainer pin 6 O'clock
18mm wristpin

Compressionheight isn't that very important, but around 38mm would be nice.

Rgds
Patrick

https://www.scafutopistoni.it/5-pistoni#s

[jbiplane]

One my coleguae produce 236cc 2-cylinder inline engines with one common mikuni carb and magneto ignition. Enhine based on Husqvarna 3120 chainsaw cylinders. When one start one of this engines it produce 30hp at 9500 rpm with propeller. 30 second later engine on a full throttle rpm drops to 7500 and power decreased. On 7500 rpm engine can work long time. The same behavior for 4 engines. Any idea how diagnose and correct situation like this?

[Frits Overmars]

One my coleguae produce 236cc 2-cylinder inline engines with one common mikuni carb and magneto ignition. Enhine based on Husqvarna 3120 chainsaw cylinders. When one start one of this engines it produce 30hp at 9500 rpm with propeller. 30 second later engine on a full throttle rpm drops to 7500 and power decreased. On 7500 rpm engine can work long time. The same behavior for 4 engines. Any idea how diagnose and correct situation like this?So the engine runs with a propeller that absorbs 30 hp at 9500 rpm. At 7500 rpm that same propeller will absorb (7500 / 9500)^3 x 30 hp. That's 14,8 hp.
So maybe one cylinder has stopped working at all after the first 30 seconds.
I've seen this happen before in a twin with both cylinders firing at the same time, but that was on an engine that heavily depended on pipe suction for its power,
something one hardly expects from a 236cc twin producing 30 hp. What kind of exhaust system is fitted? And do both cylinders operate on a common crankcase?

[wobbly]

Simple - you cant diagnose anything without data.
Fit egt and cht , this will tell you what is going on.

[Frits Overmars]

True, without data it's only guessing. But before going through the trouble of fitting EGT and CHT sensors, Valery might put his hands on the exhaust headers :not:.
The side that doesn't hurt should be the culprit :rolleyes:.

[TZ350]

The side that doesn't hurt should be the culprit :rolleyes:.

Harrrr, that is a test I can understand and I am probably dumb enough to do it myself .... Ouch dam bugger, well, that one is working .............. :2thumbsup .

[wobbly]

Haha , me thinking too hard as usuall Frits.
Best egt sensor in the world - your hand.

[Leed]

One my coleguae produce 236cc 2-cylinder inline engines with one common mikuni carb and magneto ignition. Enhine based on Husqvarna 3120 chainsaw cylinders. When one start one of this engines it produce 30hp at 9500 rpm with propeller. 30 second later engine on a full throttle rpm drops to 7500 and power decreased. On 7500 rpm engine can work long time. The same behavior for 4 engines. Any idea how diagnose and correct situation like this?

heat soak, or maybe the fuel being shaken up?
I mean this is an air cooled 2T motor running tandem north/south (hot/hotter). or is it jacketed
without a cooling run fuel etc, the intake and cases will be much hotter than starting run (charge density) and piston/bore clearance


with one carb and small differences in porting and manifold would there be a preference for one cylinder to do more work - but I guess the would happen on run 1.
A cheap IR temp gun would determine temp of each cylinders exhaust pipe

[Pursang]

So the engine runs with a propeller that absorbs 30 hp at 9500 rpm. At 7500 rpm that same propeller will absorb (7500 / 9500)^3 x 30 hp. That's 14,8 hp.
So maybe one cylinder has stopped working at all after the first 30 seconds.

Now that's Engineering at work!:clap:

cheers, Daryl.

[jbiplane]

Thanks for responce. The more information is on producer site.
http://sibaero.ru/%d0%b4%d0%b2%d0%b8%d0%b3%d0%b0%d1%82%d0%b5%d0%bb%d 0%b8/%d0%b4%d0%b2%d0%b8%d0%b3%d0%b0%d1%82%d0%b5%d0%bb%d 1%8c-sibaero-2r-i/
I nether see this engine working, only read information on Russian amateur aviation forum. Both cylinders are working (have the same themperature).

[Flettner]

left foot kick start and bob weight parts.
Ready for finish grinding, EN39B.

[jonny quest]

Haha , me thinking too hard as usuall Frits.
Best egt sensor in the world - your hand.

Even better, use wd40 or spray can with nozzle. Quick spray right at header you'll know real fast what's hot or not. Spit works good too.

[TZ350]

342426

Been playing on the dyno again tonight. Just in case you wanted to know. Green and Red lines are both standard, un modified NSR MC21 cylinders on de stroked rotary valve Suzuki GP100 bottom ends. Everything is much the same between the two engines, timing, heads, pipes etc except the Green line is on a case with much more crankcase volume and fuel injection. Interesting that both engines show little bumps in their curves in much the same places.

[Grumph]

Thanks Rob. Have you actually measured the primary compression ?

You're giving me an excuse to be lazy and leave the Villiers primary compression as it is....

[TZ350]

Thanks Rob. Have you actually measured the primary compression ?

Sadly not all that carefully but I estimate its about 770cc crankcase volume without including the transfer ducts. If I include the transfer duct volume I am guessing at about 1.1:1 primary compression ratio for a 110cc engine. But remember, you need a good pipe to make this work.

[Pursang]

Both cylinders are working (have the same temperature).

I see that the engine has a 1 into 2 inlet & a 2 into1 exhaust.

In the snowmobile world, where these exhausts are not uncommon, it is suggested that the useful rev limit is around 8000rpm.
Beyond that superposition of pulses creates interference between the cylinders.

cheers, Daryl.

[Muhr]

342426

Been playing on the dyno again tonight. Green and Red lines are both standard, un modified NSR MC21 cylinders on de stroked rotary valve Suzuki GP100 bottom ends. Everything is much the same between them, timing, heads, pipes etc except the Green line is on a case with much more crankcase volume and fuel injection. Just in case you wanted to know.

Read this a while ago. thought you might find something interesting? maybe further development

http://publications.lib.chalmers.se/records/fulltext/149154.pdf
little more info about the technology
http://www.evinrudenation.com/owner-zone/emm-unwrapped/
http://www.evinrudenation.com/owner-zone/understanding-the-e-tec-fuel-injector-by-bill-grannis/

[jbiplane]

I see that the engine has a 1 into 2 inlet & a 2 into1 exhaust.
In the snowmobile world, where these exhausts are not uncommon, it is suggested that the useful rev limit is around 8000rpm.
Beyond that superposition of pulses creates interference between the cylinders.
cheers, Daryl.

Thanks Daryl, but engine work at max for at least 15 seconds... So probably interference could not be a reason.

[Flettner]

I remember the early years of air cooled bucket racing, power would drop off markedly after the first few laps. I think it was Kenneth Steadman that first smashed the cast iron fins off that little Kawasaki's cylinder, bronze weld a jacket on, similar process to the head, water pump manufactured and fitted to the oil pump drive. Car heater radiator. That little Kawasaki would sing crisp from start to finish. The next year nearly all the buckets were water cooled.
Heat soak and thermal distortion, the enemy.

[Pursang]

Thanks Daryl, but engine work at max for at least 15 seconds... So probably interference could not be a reason.

Dunno, perhaps it takes that long for pipe temperature and wave speeds to stabilise??

Does the exhaust have a perforated rear cone?

Another question to ask: Is the fuel supply to the single carby sufficient to maintain 30hp continuously?

cheers, Daryl.

[jonny quest]

342426

Been playing on the dyno again tonight. Just in case you wanted to know. Green and Red lines are both standard, un modified NSR MC21 cylinders on de stroked rotary valve Suzuki GP100 bottom ends. Everything is much the same between the two engines, timing, heads, pipes etc except the Green line is on a case with much more crankcase volume and fuel injection. Interesting that both engines show little bumps in their curves in much the same places.

Is hump your PV's?

Also, loss of bottom end power... do you think that's from case volume... or efi?

[TZ350]

342446 Green line, much larger crankcase volume.


Is hump your PV's?

I put a lot of effort into trying to tune the hump out at 10k rpm with the PV and Ignition but could not get rid of it.


loss of bottom end power... do you think that's from case volume... or efi?

I am not sure about the loss of bottom end power, it was the first bike on the dyno. But I certainly don't think it is EFI as EFI is the easiest thing to get right at wide open throttle. Accuracy of fueling at WOT with two stroke "B" port injection beats a carburetor hands down. Case volume, maybe, but now that I know more about setting up the PV and how low it can go, I will have another look at the loss of bottom end.

[jbiplane]

Does the exhaust have a perforated rear cone?
Another question to ask: Is the fuel supply to the single carby sufficient to maintain 30hp continuously?

Yes, perforated cone
Fuel supply - I see only forum posts related this engine. Now guys trying improve there.
I want make similar inline engine based on 2 cylinders, but make something better than competitor for 115 kg aircraft use.
Hecitate what parts to use:
- 2 sets cylinders of Yamaha YZ85 like https://www.aliexpress.com/item/33017346965.html?storeId=4410123&spm=a219c.search0604.3.62.146b29a4bkrbpg&ws_ab_test=searchweb0_0%2Csearchweb201602_10_10065 _10068_319_10059_10884_317_10887_10696_321_322_100 84_453_10083_454_10103_10914_10618_10911_10304_103 07_10820_10301_537_536%2Csearchweb201603_52%2CppcS witch_0&algo_expid=b6346727-a815-4140-ad7c-652e314387d5-9&algo_pvid=b6346727-a815-4140-ad7c-652e314387d5&transAbTest=ae803_5
- 2 sets of AM6 90cc like https://www.aliexpress.com/item/32798464619.html?storeId=914279&spm=a219c.search0604.3.37.5b787b3bwMCk1i&ws_ab_test=searchweb0_0%2Csearchweb201602_10_10065 _10068_319_10059_10884_317_10887_10696_321_322_100 84_453_10083_454_10103_10914_10618_10911_10304_103 07_10820_10301_537_536%2Csearchweb201603_52%2CppcS witch_0&algo_expid=f0e463dd-11d8-4583-99c2-7ab6ebed1622-5&algo_pvid=f0e463dd-11d8-4583-99c2-7ab6ebed1622&transAbTest=ae803_5%22]https://es.
- 2 sets of air cooled Stihl 090 (I have some) https://mikeschainsawshop.co.nz/product/stihl-090-cylinder-piston-kit-2/
- last idea rework Yamaha 2-cylinder outboard using ready crank. piston and sleeves...https://www.aliexpress.com/item/32791606204.html + https://www.aliexpress.com/item/32607495304.html?storeId=117042&spm=2114.12010612.8148356.10.7cf42ceac1i6Es

Looks a bit off-topic, but may be somebody used thise spares in moto-projects and got some preferences/hates...

[jasonu]

I remember the early years of air cooled bucket racing, power would drop off markedly after the first few laps. I think it was Kenneth Steadman that first smashed the cast iron fins off that little Kawasaki's cylinder, bronze weld a jacket on, similar process to the head, water pump manufactured and fitted to the oil pump drive. Car heater radiator. That little Kawasaki would sing crisp from start to finish. The next year nearly all the buckets were water cooled.
Heat soak and thermal distortion, the enemy.

I think the bike you are referring to was called The Rat.

[husaberg]

I remember the early years of air cooled bucket racing, power would drop off markedly after the first few laps. I think it was Kenneth Steadman that first smashed the cast iron fins off that little Kawasaki's cylinder, bronze weld a jacket on, similar process to the head, water pump manufactured and fitted to the oil pump drive. Car heater radiator. That little Kawasaki would sing crisp from start to finish. The next year nearly all the buckets were water cooled.
Heat soak and thermal distortion, the enemy.

I was thinking the same as the chainsaws are designed for forced air cooling with the mag fan and shrouds and they are only used at full revs imminently in operation. chainsaw engines thus tend to have less fins than a fish fillet.
but wouldnt the in this case pusher prop drawa fair bit of cold Russian air over the engine.? i have no idea re aero cooling...........
But maybe in the way its being set up in this situation without a shroud it doesn't?
if only there was a gyro guy./microlight <_<...........

[Pursang]

The Russian twin aero engine has a cowling & fan
http://sibaero.ru/wp-content/uploads/2019/01/2R-i-tractror-front-2-1024x683.jpg
http://sibaero.ru/wp-content/uploads/2019/01/2R-i-pusher-1024x723.png

Looks like a lot of development was done.
Don't read Russian so can't tell if this is a design problem or a fault with some individual installations.

cheers, Daryl.

[Flettner]

Disclaimer, I did not do this video. A fellow gyro nut posted it. It's a bit OTT, but it does show that the 700 twin is a real thing and does in fact fly. These are early hours so I'm just using enough power to fly, no where near full throttle, too frightened I'll blow it up. But it goes well.

Jbiplane, I know weight is an issue for you but a balance shaft is nice, at 180 degree firing coupled with this shaft my engine is nearly electric motor smooth and so is water cooling very desirable for sustained high power settings.
Make your own cylinders then you get exactly what you want not someone elses compromise.
https://youtu.be/sm8Y0XWEpIU

[husaberg]

The Russian twin aero engine has a cowling & fan

cheers, Daryl.

What video engine was i watching what i seen looked like an opposed twin?
https://i.chzbgr.com/full/4702467840/h15D2A0F4/


Disclaimer, I did not do this video. A fellow gyro nut posted it. It's a bit OTT, but it does show that the 700 twin is a real thing and does in fact fly. These are early hours so I'm just using enough power to fly, no where near full throttle, to frightened I'll blow it up. But it goes well.

Jbiplane, I know weight is an issue for you but a balance shaft is nice, at 180 degree firing coupled with this shaft my engine is nearly electric motor smooth and so is water cooling very desirable for sustained high power settings.
Make your own cylinders then you get exactly what you want not someone elses compromise.
https://youtu.be/sm8Y0XWEpIU
i was wondering why it looked like you were in a valley until i got to the end.

[F5 Dave]

Gawd! Looking at the top of those trees made me want to faint..

[Flettner]

Thats why I fly over the gap in the trees. More choices if the engine stops.
Shafts ground and parts fitted.

[Flettner]

I think the bike you are referring to was called The Rat.

yes the rat bike😆

[Pursang]

What video engine was i watching what i seen looked like an opposed twin?

Early lightweight cycle-car powered by opposed twin.....
http://images2.minutemediacdn.com/image/upload/c_fit,f_auto,fl_lossy,q_auto,w_728/v1555924390/shape/mentalfloss/620godina.jpg.

[Flettner]

Early lightweight cycle-car powered by opposed twin.....
http://images2.minutemediacdn.com/image/upload/c_fit,f_auto,fl_lossy,q_auto,w_728/v1555924390/shape/mentalfloss/620godina.jpg.

Nice------

[husaberg]

Early lightweight cycle-car powered by opposed twin.....
.



Nice------

Oh i see now the Chinese are doing Siamese exhausts as well

[katinas]

Use a Vt250 gearbox nice ratios strong gears quite narrow, millions made available from any wrecker in any country. nice clutch, available in 5 or 6 speeds as well. also the same gearbox is used on the MVX250 an fthe CBR250
they have an intersting gearshift set up though almost planetary. available either push or pull left or right clutch.

342385342386

Interesting article about VT250 Turbo version 53Hp and racing NR 250 oval, but looks like on the illustration some mistake about NR power, maybe it could be 103 hp 18000rpm., not 53hp, like on the street version.

https://japan.young-machine.com/2018/10/14/10926/

[husaberg]

Interesting article about VT250 Turbo version 53Hp and racing NR 250 oval, but looks like on the illustration some mistake about NR power, maybe it could be 103 hp 18000rpm., not 53hp, like on the street version.

https://japan.young-machine.com/2018/10/14/10926/

Cheers i think this was where i first seen about it.
https://cx500forum.com/forum/cx500-cx650-turbo-forum/25885-honda-other-turbo.html

[katinas]

Want to say thanks again to this forum.
Boy show good result in today s MX65 World Cup qualification, with rounded piston in 4th place.
Most modification on the engine was from this Kiwi thread.
Thanks

[Frits Overmars]

Want to say thanks again to this forum.
Boy show good result in today s MX65 World Cup qualification, with rounded piston in 4th place.
Most modification on the engine was from this Kiwi thread.
ThanksThank you for the feedback Katinas :niceone:.

[TZ350]

Boy show good result in today s MX65 World Cup qualification, with rounded piston in 4th place.


............. Brilliant.... :2thumbsup

[TZ350]

342463

Very satisfying to see Blair on Team ESE's GP-NSR110 being total dominant in the prelim race and taking out a :first: at Hampton Downs today.

DNF'd later with a massive slide into the kitty litter.

[F5 Dave]

Looks a little wet there Rob

[TZ350]

Looks a little wet there Rob

Yep, raining cats and dogs at one point.:yes:

[katinas]

Sunday warm up 6th place, but race with little drama.

After first fall in race 1, boy cant start up engine too quickly and ended in 39th place.
In race 2, after two falls, finished in 9th place.
Nice experience and Italian fans was amazing.
After two weeks time, final all European MX65 championship round.

Just want to say that after dyno tests we stick to std KTM exhaust pipe and std reed cage.
We tested HGS pipe and V force reed block, but both work in the same way.
Max power was same like with std.
Over revs with little higher power.
But too much lost at mid range.
Maybe with rounded piston ( 1mm and knife sharp at C ), HGS exhaust tailpipe is too small, but we didnt test HGS with std piston.

We tried rounded piston (with other mod) on other three racers KTM engines, ( two 50, one 65, one 125) and they all were very happy. One
SX65 engine goes to Ireland championship and after the first race was surprises how it goes so well with std pipe.
I decide to try this on my sons Yamaha Why scooter, with intention not to change any original parts. Just modified head, rounded std piston, wider than crankcase intake to C on cast iron cylinder ( aprox 1.5 mm step on crankcase ) std exhaust and speed goes up from 60 to 75 kmh with much stronger acceleration.

Thanks again Frits about this idea and many others about nice two stroke things.

[Frits Overmars]

My pleasure Katinas :D.

[wobbly]

Katinas - with 1mm radius how much did you drop the cylinder , and with no radius on the boost where does its timing end up
compared to previously.
I have tested 0.75 and 1,5 radius with lowering the cylinder 1/2 the radius.
But have not tested the uncut boost port idea - want to copy what you have found to work already.

[jonny quest]

Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported atleast 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.

[husaberg]

Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported at least 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.

For road racing the old numbers were .65-.75 with .7 being very reliable in my experience.
You also need 2mm each side to seal according to bell.
You can put your cylinders on the other way and the wear will move to the exhaust side.
I can't remember what the TZ was that they ran backwards but that was the max practical limit on the model before using that available tech at the time.
He googles G model



Husa was of course exaggerating about the piston mileage in the Yamaha TZ250G but apart from that I must agree with him on all accounts.
The TZ250G was remarkable. Power-wise its cylinder block was a big step forward, with better transfer ducts, smaller exhaust duct volumes and the huge inlet ports that were detrimental to piston life.
The following year Yahama reversed the direction of crankshaft rotation by means of the jackshaft, but we'd already found a much simpler solution: we reversed the cylinderblock on the 'G': piston problem solved.


Although it might appear to be flippant, I actually wasn't Frits, it was out of McKellar’s Yamaha twins book, he lists 80-120 KM piston mileage and cranks not much more. With 53 Rear wheel hp 43mm inlet port width and a 4mm Sinusoidal port roof. More curving yet flat roofed transfers
Slightly larger Front forks were added as well.
The official recomended replacement of pistons on the G i believe was per race.
Along with the Jack shaft and the changed bore and stoke the H was also the first year of the PV, it has bigger big ends, lighter crank wheels and a different crankshaft coupling resulting in less crankshaft flex.
Base mounted cylinders 44mm intake port width 23mm ex port height and 55 HP. But of course more importantly much greater reliability.

Funny enough as you know yamaha, eventually followed you. (and MZ)


I did the same trick of putting a bridge into the intake on a 350G - 6 port cylinder, as it now has reed boxes on the back.
This allowed a much wider intake width, and then I added an extra pair of boost ports up each side of the welded in bridge.
Works well.
Hummel and Chevalier did some cylinders for the 250 with a bridged intake that worked well also.




I have a TZ250G with the inlet port about the same size as the bore. My solution was to weld a 6mm wide vertical bridge in the inlet port which was then shaped into an old cylinder that needed to be re-plated. Early days but this seems to give better support to the rear face of the piston to guide it down the correct hole .l My reasoning also included that since it was in direct line of the conrod there was little reduction in effective port area.
Reversing the cylinder would mean new pipes etc so this solution have the least effect on the rest of the bike. Also wanted the bike to look "original". Also managed to find a stash of 30 "G" pistons which are 54.25 mm rather than 54.00mm !! And no - I do not want to sell any.
Comments anyone ? ( Especially Frits Overmars )

So the tz250G was 79.6%
The TZ250H 78.5% and was reliable with the jackshaft. ie same as reversing cylinder
Bridged 100%

[Pursang]

I'm Drag racing application.... but it broke the intake skirts after about 12 1/4 mile runs.

I'm sure Top Fuellers & Pro-Stockers would Kill for 12 runs from a set of pistons!

Cheers, Daryl.

[katinas]

Wob, it is really interesting how different capacity engine react to piston radius. We tested seven different engines on dyno and ended with different cylinder height, but looks like 50cc needed most cylinder drop from factory settings.

KTM Sx50 -piston radius 0,7mm Cylinder down 0.5mm from std (best max 14.2 hp)
KTM Sx65 - piston radius 0.5mm Cylinder up 0,2mm from std (best rmax 18.2 hp winter, at 8500rpm 11hp )
KTM Sx65- for World cup piston radius 1.0mm Cylinder down 0,2mm from std ( best max 17,33 hp summer, at 8500rpm 13,5 hp )
KTM Sx125- piston radius 0,5mm ( not mached head) Cylinder up 0.9mm from std ( best max 31,8hp and same mid range like on std with max 28hp)

We never compensate C duration losses when lowering cylinder, but only because if something goes wrong it would be not possible to rise cylinder again for tests, but maybe with restored C, engine goes even better.

Its difficult to to stick to one rule for duration with rounded piston, but with sharp at C this is really work. With bigger than 1mm radius, maybe something needed to be done with exhaust pipe, as those is harmonized with non rounded piston.

Very first time testing on dyno was with full rounded piston 0.7mm on 65cc with some gains, but over 1mm no gains, reaction was very similar to your tests.
But other variation, with full rounded piston more than 1mm, maybe could be much lower duration for C than A and B.

Add SX 50 piston photo

Cheers

[koenich]

just for clarification - what does cylinder up/down mean?

up - e.g. raise it with different gasket beneath cylinder?
down - e.g. turn it down on a lathe?

was squish always kept constant?

[andreas]

The rd project

[TZ350]

.
Andreas I love your bike stand. I have one like that under my BSA but yours is more innovated. :yes:

342476

[Frits Overmars]

Andreas I love the bike stand. I have one of those myself. :yes:What do you call this material? Pre-carbon?

[andreas]

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Andreas I love the bike stand. I have one of those myself. :yes:

Ha ha, piece of art.

[andreas]

What do you call this material? Pre-carbon?

Yes natural carbon fiber.

[katinas]

just for clarification - what does cylinder up/down mean?

up - e.g. raise it with different gasket beneath cylinder?
down - e.g. turn it down on a lathe?

was squish always kept constant?

Yes you right I must correct.

Up - how much raised cylinder from what we started with non rounded piston ( mainly from factory base gasket setting)

Down - how much lowered cylinder from what we started with non rounded piston ( usually enough thinnest gasket )

Squish kept constant and head volume too and this is little frustrating work.

[F5 Dave]

Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported atleast 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.

Very carefully monitor bore wear everywhere and clearances. That will break off piston skirts. It might be you can get away with slightly crazy width but only while fresh.

[jonny quest]

These RD400 cylinders are at .655. They had .003" piston clearance, running ProX Blaster pistons. Maybe I just need to tighten them up to .0018"... and cringe, use Wiseco Forged.

The side that didn't break has extensive wear on piston skirt. And you feel it rub on port pushing piston up and down in cylinder.

There was no detonation.

[wobbly]

Thanks for the piston radius info.
My first reaction would be that if the cylinder reacts best with the radius AND then being lifted, this would mean straight away
that the cylinder was way low anyway , and would be better being lifted even with no radius.
If you plot in CAD what happens to the effective timing when adding a radius , it works out that the original timing is achieved
when lowering the cylinder exactly half the radius ( using a 0.7 feeler gauge as a stop , to change the piston movement by exactly 1mm ).
I have done alot of work on this in the kart engine and found that a full radius gives really good front side power increase - but at
the expense of too much overev power.
But I have just tested lifting the boost port as the latest Modena has it positioned 1/2 way between the A and B.
This did exactly the opposite - really good overev at the expense of front side power.
So Im thinking now that the radius , not cut above the boost , along with lowering the cylinder will give me mid range , then lifting the boost
will add the overev.
As you say , having to cut special heads to achieve this really is a pain.
But hey , if it was easy everyone would be doing it.

[husaberg]

These RD400 cylinders are at .655. They had .003" piston clearance, running ProX Blaster pistons. Maybe I just need to tighten them up to .0018"... and cringe, use Wiseco Forged.

The side that didn't break has extensive wear on piston skirt. And you feel it rub on port pushing piston up and down in cylinder.

There was no detonation.
The RD400 already has a poor rod to stroke ratio std
Longer rods will also give the skirts a longer life as it will decrease thrust on the faces.
KTM200 118mm rods should work with what you have.
Blaster pistons are a fair bit shorter than RD400 ones. Which will make it worse. .
woosner do forged it175 ones. they also used to do single ring DT175 ones for long rod rd400's
ALso oem Yamaha single ring pistons are available for the YZ175 NOS anyway. no idea re their lengths
Plus TZ750 pistons were in similar sizes.