when im rompin on the gas givin full throttle an i back off and engine brake, my kfx400 sometimes wants to shut off an i need to pump the gas with clutch in to keep it running. its like it is starving for gas. any suggestions to why? or what i can do to find the problem. it only does it on occasion especially after it sits a week or two without being ridden.

 

The exact same thing happens on my street bike which I ride not too often - engine stalling whenever I come to stop. I have to rev up the engine in neutral keep it running. In my case, it is the pilot circuit of the carb getting slolwy clogged up by old/gummy gas. I put some carb cleaner like Techron into fuel tank and rode for 30+ minutes at high speed and the bike started running normally again. One way to prevent this is to put some Stabil in fuel tank if you will not ride the bike for a while.

 

Change your spark plugs.....