My friends 99 Formula Z 500 dies after a half a mile of riding, carbs have been cleaned, raves are ok. It does have spark and even if we prime the hell out of it still no start. After 15 minutes it will start and run again until it gets hot. Any ideas, it appears to be running a little hotter then usual but I'm not sure if it is related. We are going to check the quality of the spark when it runs and compare it to the spark when it dies. Plugs appear very dry but the primer on this type engine bypasses the carb and shoots it right into the carb boots. This started last weekend and since this sled was new has never had a problem. Any ideas