I just bough a 99 banshee which is supposed to be bored out to 377 cc and it has LRD headers, and I don't know what kind of silencers...

Anyways, it has a trinity racing single carb set up, and I am having trouble jetting. It has a "178" main jet, which has been drilled out because it looks huge. I bough a 220, and a 210, the result wasn't very drastic. It seems pretty strong off the bottom end, but it kinda falls flat on top, it makes noise, but the power isn't really there. Sorry that I am so vague, I am new to two strokes, I used to ride an XR250 dirt bike, so I've never really dealt with this problem. Does anyone else have the single carb set up on their banshee?

Any help would be great.

 

how do the plugs look? do they have much color or do they look lean as hell. when the power falls off, does it sputter at all or just like it runs out of fuel? I wouldn't think you'd need more than a 210 or 220 unless you have an air leak. If it was a stock bore/stroke, I'd say you'd be good with a 178, 180 or somewhere close, but I'm not experienced with that carb when bumped to a 370 or so, but it shouldn't be too much. My personal gut feeling tells me a 200 or 210 should be plenty and maybe more like a 195.

One big question, what kind of reeds does it have? I'm assuming it's the Trinity manifold. If it has vforce reeds and the manifold has the oring seals, instead of a full gasket, then that's an automatic leak where the reed cage meets the manifold, but it's very hard to tell by the old carb cleaner/propane trick. You have to run the gasket on the trinity manifold, not the orings. so you might check that. i learned the hard way. when i set mine all up, I was running a 180 main and all of a sudden it needed much more, I went all the way to a 230, keep in mind it's a stock motor, and was like WTF!! Turns out, the orings were leaking above half throttle. Got the gasket and everything's nice.

You might also call Trinity Racing at 877-FASTOYS and ask for Jim. He can help you out with a good jetting baseline for that.