Yamaha QT50 Has Inconsistent Idle and Randomly Bogs Down

Evan Faucher /

I have a 1985 Yamahopper QT50. It will go from riding great and hitting 30 mph for a long ride to bogging down and only hitting 10 mph the next time I take it for a ride. There are no adjustments being made between the rides. I have cleaned the carburetor, new fuel lines and filter, and just went to premix gas and stopped using the oil pump. It tends to have an inconsistent idle and can go from high rpms to low while just sitting on the stand. I need some help, any advice would be much appreciated, thank you.

Re: Yamaha QT50 Has Inconsistent Idle and Randomly Bogs Down

I'd take the carb apart again. make sure you get the long orifice tube out under the pilot jet and tap out the jet that sticks up slightly into throttle body. These two jets go unnoticed because they are hard to see and sometimes hard to get out- especially the one that's screwed in. Here's the one that's tapped in and sticks up into throttle body a little


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