Yeah, you need to have him check the plugs and make sure that it is jetted right. Then take the clutch cover off and check the impellar, the drive gear, hoses, the radiator cap itself, good coolant. If that all checks out then look at the way that he is riding, WOT and spinning the tires doesn't move too much air through the radiator. The next thing I would do is get a NOSS or Cool head for 250 or so and put it on yourself. These increase the coolant volume by increasing the area where the coolant flows and they also change the flow path to help in cooling.............