Hi, I recently bought a 2005 RM-Z 250f. Bike has recent rebuild. Checked the valve clearences today. All of them are within specs. New spark plug. Fresh gas. No excess engine noise or popping on decel. Bike starts excelent when cold 1st or 2nd kick. Runs very strong with lots of power. But after about 5 minutes of riding it is very difficult to restart. Tried using the hot start lever but not sure if it is working. How can i tell? Bike has full Pro-Circuit Ti-4 exhaust system. any ideas what the jetting should be? and what i should look at next. Any input would help. thanks.