I have a 2000 red 300 4X4 and the carb is spitting gas back into the air box, also filling cylinders with gas. Any recomendations besides a new carb?

 

Sounds like the float is sticking. Try removing the carb and cleaning the float bowl and needle valve. You could have something stuck on the needle or a bad needle seat.

More than likely it is just gunk causing the needle to stick open.

If you are getting fuel flowing into the cylinder and air box as you suggest you need to change your oil as well. The fuel can seep around the rings and get into the oil. IF you run the engine too long this way it can mess it up pretty bad.

Swampy