Oil spray out of exhaust tip of the front cylinder. Also dripping out bottom of (JHA??) rear cylinder expansion chamber (which has a pin hole down there, for some reason). Black and smells like fuel/ oil mix. Seems to be getting worse.
Ya know, the tip of the front cylinder stinger is wet, but spray/ issue may be the drips from the rear cylinder expansion pipe blowing back on the bike....
Ideas?
Thanks
Jeff

yep, welcome to 2-strokes Messy little things!

The only option I have come across for not getting the mess from where the exhaust mounts to the cylinder is to cut a couple grooves into the exhaust manifold for the after market type exhausts that slip on and are held in place by springs to the manifold. In those grooves, I put high temp resistant O-Rings so you get a nice tight fit.

beyond that, stock always has some mess, and after market exhausts need some form of sealing to keep things clean. Tried chamber seal, but that was worse then without.
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Charles Gallant

Thanks much, Charles. I don't have this problem (to this extent) with my other two-strokes. Will take a look at those areas. My main curiosity is why there is so much (apparent) blow-by or fuel getting past the plugs/ cylinder. I know we're not supposed to talk about jetting....
Thanks
Jeff, Ohio

there are plenty of possible reasons a bike runs rich. Jetting is a good start

From there you can check the RC Valve's, Timing, oil pump, etc..

Check out the tuning section for help on all these areas.

As of jetting, Andy is trying to keep out detailed specifics to be discussed here in the open area. This is due to people who may not understand jetting, getting advice and their lack of understanding causing damage to their engine. Keeping discussions to a high level keeps that problem from coming up.

There are some really good books out there on 2 stroke jetting/tuning. A graham bell has one, John Robinson has another. Of course they don't cover the specifics of an NSR250, but a lot of information they cover in their books will work for the NSR.
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Charles Gallant


Last edited by cgallant on Wed Aug 19, 2009 7:06 pm; edited 1 time in total

Subscribed, so will look around over there.