The coolant system on my '02 YZ426 is over pressurizing and shooting coolant out of the overflow. We have replaced the head gasket twice; resurfacing the head and cylinder each time. It isn't overheating per my Trail Tech thermostat and the Pro Circuit heat strips on my radiator and head. It overheats as it runs out of coolant but not before. We put a higher pressure radiator cap on and it slowed the spit but didn't fix it. The only suspect I can think of is if the radiators are clogged. Is there a way I can test their flow? Any other ideas? Someone help!