I have torn my carb. apart and the vacum cup may have a pin hole in it. It doesn't rise whenever the engine is turning over. What is the purpose of this vacum cup? The engine will crank on choke and run but off choke the engine will idle for a long time. If I give it throttle the engine shuts off. Any help would be appreciated. Thanks, Stumper

 

Those CV carbs are junk. Much better off to get a non-cv carb and jet it yourself or find someone who can jet it for you. THe vacuum cup you are talking about actually opens the throttle as engine vacuum goes up. All you do when you give it gas is open a butterfly valve. A non-cv carb you control everything with your thumb. CV carbs are a pain and I refuse to work on them. Its cheaper in the long run to buy a simple carb that works and that anybody can fix if need be.

Google CV carbs and read up on them.