GN250 tuning for muppets

[general-lee]

I'll be brutally honest when it comes to carbs I am hopeless. And I could do with some advice based on Suzuki GN/DR/TU 250 engines specifically.

I have bought a TK speedpump carb designed for the GN, I've whacked a pod filter on it. Almost works without messing about, but flatspots when you try to go past 4,500 revs.

I've turned the air screw in a few notchs and it has deffinately helped, but I believe jetting the carb is the ideal route.

I have purchased a 135, a 137.5 and a 140 jet, I'm assuming the 135 jet will suffice but got the 2 above just incase.

Am I going about this sensibly? And before anyone says it yes I know the GN 250s are pointless to tune, but I'd like the full potential of the carb.

Thanksin advance, Rich

[stinkwheel]

The air screw has absolutely no influence on your carburetton at 4,500rpm. It only alters the mixture at idle.

The jet diameter controls carburettion at wide-open throttle.

At other rev speeds, the relationship between the jet size and the needle profile and height are what does it. The needle profile is probably responsable for the flat-spot. Altering the needle height may help.

An airbox will usually flow more air than a pod filter anyway, I'd suggest putting the airbox back on.
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