ESE's works engine tuner

[F5 Dave]

RZ slipping clutch; I've never looked at this sort of thing as assumed a drag thing, but Wob was posting of issues and the night before my RZ started slipping on the dyno at anything approaching 90hp (its a CPI 496cc).

So what is having a lockup clutch like? It applies pressure, but does it change the action so it feels weird?

Wonder if it needs a spacer.

http://m.ebay.com/itm/NEW-Yamaha-Ban...257Ciid%253A11

[adegnes]

An idea I've been playing with for a while now:

As I'm not restricted by any rules or regulations, how about a supercharged "hyprid" two stroke?
Blower connected directly to the transferports, a relatively small exhaust port, a pipe designed to retain as much energy as possible before the convergent cone(a pure "port blocker"), and an electric motor for bringing it into the powerband.

The point being to blow huge amounts of fresh mix through the cylinder, eliminating any possibility for mixing with spent gases, and at the same time (due to the small exhaust port/blocking pipe) build considerable pressure before exhaust port closing.

Stupid?

[peewee]

Yes, at least best as I can. The Problem is that I can't make a real oval as I would get into the water jacket, so I try to make the aux tunnel as far and "wide" as I can... Also I will put the stinger nozzle in, EngMod predicted a nice power increase behind peak. So let's see what the dyno will tell

I understand. sometimes you just do the best you can and leave the rest to compromise. to get down to 75% i ended up needing to do a lot of welding on the floor and roof of the main passage. was pain in the ass . the cylinder was designed sometime in the early 80's and really there was nothing good about its design. sometimes i wonder if it was just a big waste of time. hopefully your adventure is less grief than mine

[adegnes]

sometimes i wonder if it was just a big waste of time.

No way! Think of all the experience and knowledge you've gained from it!

[peewee]

Not likely; the 125 cc KTM GP-bike already had an injector in the crankcase that injected through a port below the exhaust port.
They used it instead of a powerjet and it would only have been logical to use the same setup for full EFI.
Attachment 328804 Attachment 328805 Attachment 328806

ktm been using 3exh port configuration in the motox engines for 30yrs now. wouldn't you think that experience would carry over to the road going sector ? ive really gotten to dislike the center bridged exh after bad experience with it chewing up rings . luckily ive sold off nearly every bike i had with a center exh bridge

[richban]

Attachment 328803
Anyway 151 runs latter, 23 hp. In the end there was still a cyclic series of humps, interesting, no idea how to smooth them out.

Looks like your classic 4 banger Exhaust reversion. Was it there with the old cam timing? I can't find my old Graph from your dyno. Mine might have had it as well. Fix should be all in header length and muffler size.

[teriks]

Silicone, or RTV?

Would be good for alcohol fuels, but silicons doesn't like gasoline at all.

[jonny quest]

Here you go Jonny.
Attachment 328808 Attachment 328807

Thank you! Did that have a 180 firing order?

[Frits Overmars]

Thank you! Did that have a 180 firing order?

Nope. It was 90°/270°, rather unusual for a parallel two-stroke twin.

[husaberg]

Are there any pics out there of KTM'S parallel twin 250 gp engine? I tried searching with no luck

Here you go Jonny.

Here is a few more, Internals are pretty much race Kit NSR/RS Honda. AS are the pipes
https://www.kiwibiker.co.nz/forums/a...p?albumid=4901
Pipe spec courtesy of Frits Overmars bottom.
https://www.kiwibiker.co.nz/forums/a...hmentid=310144

[Nath88]

Does anybody know if there is a good heat and fuel/oil resistant liquid rubber a carburetor insulator boot could be made of?

I have a 3D printed TPU (Thermoplastic Polyurethane) boot on my bike at the moment. Printed by Duckhive3D. He's done a few for bikes and karts, it might be an easier option. Or possibly cast it using TPU.

[TZ350]

Attachment 328803 In the end there was still a cyclic series of humps, interesting, no idea how to smooth them out.

Looks like your classic 4 banger Exhaust reversion. Was it there with the old cam timing? I can't find my old Graph from your dyno. Mine might have had it as well. Fix should be all in header length and muffler size.

Worse at the beginning, got better with each positive change to cam and inlet tract length. It has a tapered and stepped header. If there is another time on the dyno with this bike, we will follow your suggestions.

[richban]

Worse at the beginning, got better with each positive change to cam and inlet tract length. It has a tapered and stepped header. If there is another time on the dyno with this bike, we will follow your suggestions.

Cool yeah sounds like you just need to match up the exhaust. I ended up chucking out the stepped header in favour of a more 2 stroke style header. The size increase was with a steady cone instead to hard steps. My engine was very sensitive to any hard pipe transitions. Stupid things anyway to many moving parts.

[crbbt]

Just curious what happened to all of ktms 125gp bikes? Can not say I recall seeing any at club level. were they only a factory effort?

[SwePatrick]

RZ slipping clutch; I've never looked at this sort of thing as assumed a drag thing, but Wob was posting of issues and the night before my RZ started slipping on the dyno at anything approaching 90hp (its a CPI 496cc).

So what is having a lockup clutch like? It applies pressure, but does it change the action so it feels weird?

Wonder if it needs a spacer.

http://m.ebay.com/itm/NEW-Yamaha-Ban...257Ciid%253A11

Yes, clutching it in high rpm will be harder, sometimes impossible.
You need a shiftcut with that.