I've completly rebuilt the engine on my 1978 440 Exiter. New electrical, rebuilt carb, new fuel lines, cleaned clutches etc. It starts and idles good, but it bogs down at 40 mph. I took it all apart and rechecked the seals etc and all looks good. I took the the airbox off and noticed that it runs great, no bogging. I took the airbox apart to clean it, but nothing appeared wrong with it. I put it back on and the same problem occurs with the bogging at 40 mph. Does anyone have any ideas on why the airbox would cause this? Thank you.
sounds like a jetting or mis-adjusted fuel screw issue. in essence, with the airbox installed, your reducing air flow. with it off, increasing air. somehow your upsetting the fuel to air ratio. need to do some carb tuning.
Yep I agree. It is running rich and when the air box is removed it sucks more air and that leans it out. Then no more bogging. Do a thorough cleaning of the carb and I'm guessing something is not right. It has the butterfly Keihin carb...right? You rebuilt the carb, so maybe the float needs to be adjusted or something... wasn't put back together right. It happens. Maybe someone can help with the float setting. Go through the carb with a fine toothed comb and you will find the problem.
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