Leaderboard

It could be a fault in the carb, a lot of the aftermarkets aren't very strict on quality control. the main jet could be oversized a few thousandths and that would affect running. The only adjustments on these Honda carbs, besides the Idle speed adjustment, is the Mixture screw on the side of it, Some of these have them, some of them don't. If your carb has this adjustment screw, the proper way to set it is to warm the engine up, and adjust that screw in or out, until the engine reaches it's highest Idle RPM, that's where the engine is getting the most fuel. you can turn the screw in about 1/16 to 1/8 of a turn that will lean the mixture out just a little bit. you may now need to readjust the idle RPM with the plastic screw on top of the carb. If it still runs rich after this, most likely there is a issue with the aftermarket carb, i had a problem finding a carb to fit the GX390 on my pressure washer, i finally bought a OEM Honda carb.

I bought one last april. You will have go over every nut, bolt, etc to make sure they are tight. grease all available fittings. Also front and rear diffs were low on fluid. Make sure you follow breakin period. might be missing rubber bumpers for box. mine runs great, haven't had any issues other than that noise on initial takeoff. I have 70 miles on it. it does run better with time, make sure you use 91 octane in it.