I"ve got an 06 grizz that is all stock, after riding a while like running half a tank of gas through it some times it starts cutting out and stalles and won't restart like it ran out of gas, it seems that when i take the gas cap of it vents a lot of air and it starts right up after, i've checked the cap vent tube and it is not plugged, anything else that could cause the gas tank to hydrolock or it the cap and vent bad?

 

If it's like stock banshee caps,there's 2 or 3 screws that holds the guts (not sure what it's called) in the cap.Just take it out and see if that helps.Keep in mind though that if you flip the quad that there is nothing keeping the fuel from pouring out.It would tell you though if the cap was bad.

 

You might have some dirt,trash,etc... in the cap.Never heard of this problem but there's a first time for everything.

 

mine did the same thing after a day of riding int the mud. I somehow managed to get mud in the vent tube. Cleaned it out and now it runs fine. Also maybe check your fuel filter.