Thanks Krominator, and to you and yours too. Yeah the bike ones are dearer than auto ones.. If a thermostat is going to cause an airlock in the system, then the thermostat for that machine has a small hole it it to let the air out. The hole needs to be at the top. Other than that though the cooling systems these days are generally designed to self bleed.. But sometimes on a bike that might require a small hose from the top of the motor going straight up to the radiator. If that hose gets blocked or kinked it can cause an air lock problem.. Sometimes some of the radiator hoses look like if they were routed wrong it could cause an air lock too.