Tri z 250 bottom of cylinder leaking

[El Camexican]

Good to hear you have the tools for it. Personally I’d only raise that exhaust port 1mm to start. You can always go more later. If you happen to be pondering the extra boost port, do some reading on it. They have been known to cause catastrophic cylinder failures if not done properly.

[Paul G]

Did a little porting and polishing think I need to go up a couple jet sizes where can I get bigger jets the one I have is stock #470 can't seem to find any bigger ones. Anybody can tell me where to go would be cool or order. Thanks

[El Camexican]

Did a little porting and polishing think I need to go up a couple jet sizes where can I get bigger jets the one I have is stock #470 can't seem to find any bigger ones. Anybody can tell me where to go would be cool or order. Thanks

Try jetsrus.com

[Paul G]

Just started the bike 3rd kick never had started that fast before. Idled great rode it around a little till warmed up. Shut it off checked all the fluids topped off coolant. Started it back up rode it around again till it was warmed up. Then got on it no powerband started cutting out. Now it will start idle give it 1\4 throttle and it reves up then down then up and right before it does and backfires and blowers my expansion chamber in half its a two piecer. Any thoughts you tri z guys

[ironchop]

.... backfires and blowers my expansion chamber in half its a two piecer.....

Literally?

Holy cow!



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[El Camexican]

What all did you do to it? Did you end up splitting the cases, or just doing the top end? The only time I had an engine behave like that was one with a power-valve that was stuck closed, but that's not your issue.

Any chance you put the piston in backwards? There's window on the intake side, remove the pipe and turn the engine over while you're looking in the hole. If you see an opening in the piston skirt its backwards.

[Paul G]

Nope piston is in correct took the carb apart found the throttle needle was bent and recleaned everything changed spark plug. runs great now think I fouled the plug in the beginning I put some 2 stroke oil down the plug hole a couple hours before starting it pre lube.Did not split case. Got all my surfaces flat. Did port the intake and exhaust still have stock main jet going to check plug after a little more riding tomorrow. I think it was just the carb i could a screw the air mixture in further than before maybe there was something in there?

[El Camexican]

A bent needle will drive you nuts, glad to hear that was all it was. Did you pressure test it after assembly?

Not sure what you mean about the air screw. It should bottom out softly and close about the same time.

[Paul G]

this is the bike before we took it apart.

[Paul G]

I ment mixture screw its only one mixture screw from what I see on the right side above the bowl. Pressure test came out great have a few jets on there way.

[El Camexican]

Air screw/mixture screw are one of the same when located in front of the carb slide. If located behind the slide it’s still a mixture screw, but in that position it controls fuel flow instead of air. Those are usually in 4 strokes.

So you say you can turn it in a lot further now? Weird unless you removed a washer, or there was crud behind it. You might want to pull it out and make sure that the tip didn’t break or something. Usually the air screws are pretty simple and robust compared to the fuel screws due to the fact that they don’t have to see you as well, but it still worth checking to make sure that everything is in good shape

[Paul G]

Will do going to check it out first thing. Then run it around check plug see if i need to jet it up.

[El Camexican]

I don’t know what carburetor you have on there, guessing stock?

You might want to check the parts fiche to see if there is a washer, or gasket in that air screw set up. I know on some of the Keihin carburetors there isn’t, but I think on the Mikuni’s there is.

[Paul G]

Got the carb tuned in went up to a 480 main jet runs perfect. now time to brake it in. Just have to make brackets for new front calipers.