My arctic Cat has trouble starting?

My arctic CAT ATV has trouble starting after it has been running for a while and when the fan kicks on. I hit the starter and have to push in on the trottle to get it started. Like I said only after it pulls heavy loads or is getting a good workout. We use it for farm activities. Every once in a while when it hard to keep it runing it will back fire and then start up? What do I need to look at or do?|||it sounds like a carburetor issue. try to tune it up, your idle sounds like its set low. then when you push the throttle while starting, it is probably loading it with fuel then abruptly combusting, causing it to backfire. it starts after because the system is "cleared" and new fuel is allowed to do the same. I'd say tune it up...and it is probably running really rich, and you may be flooding it when you're pulling those loads and giving it more gas, in my own opinion|||MY POLAR BEAR BIGGER|||if there's an automatic choke on it that might be faulty or if its injection it could be the cold start injector