075 problem

[guitarborist]

I am having a problem with my 075 on full throttle. It revs up fully then starts revving up and down. I just rebuilt the carb. Before the rebuild it was not having this problem. I scraped the mating surfaces for the new gaskets and the jointing areas look good but the carb to throttle body gasket is not quite like the the original. It does not cover the entire surface, the area around the opening and around the mounting screw/post are covered but not out to the edges of the carb and throttle body. I think I must be getting air in under the carb when the revs build and vibrate at the right frequency, the problem is only at full throttle. Does it sound like this where my problem is? Could I use gasket sealer or maker to seal the area where the new gasket does not go to? Am I missing something else that could cause the problem?

Thanks for your help

 

[Lakeside53]

NO SEALER on the carb gaskets...

What carb do you have?
What kit did you get?

Did you put the gasket/diaphragms in the correct order - note these reverse order one side to the other.

Pump cover -> gasket-> pump diaphragm->carb body
Metering cover -> metering diaphragm -> metering gasket -> carb body.

Make sure the metering arm spring is straight and in the arm detent, and not buckled under, and the arm is adjusted correctly.

 

[bullseye13]

There is a brass governor plug in your carb. It could be leaking causing the irratic running, or your carb is set too lean and the governor is opening letting in more fuel. To me it dosent sound like you have an air leak, but it is always possible.

 

[guitarborist]

Found the problem. The vaccume hose from the carb to the crank case was leaking. I replaced it and all is well. Thanks for the help.