Hey, My 300ex stalls every 10-20 mins just for no reason. It wont start up unless I open up the gas cap and let the air out. Then it starts up perfect. I have no clue what the problem is. Please help.

 

I bet the end of the little black hose that comes out of the gas cap is sucked to something on the frame and can't get air. Thats what happened to my quadsport once. I took the end of the line and cut it slantways so it couldn't do that anymore and has worked great since.

 

Its either the hose is too long and kinked or the "bearing" in the gas-cap, I'd take it apart and take that stupid ball out... at least they yammy had one... would do the same thing as yours..