My raptor 686 overheats, boiling out the overflow. The radiator cap is good and the cooling system holds pressure. I hooked a gauge up to the radiator and it builds pressure over 20psi, the cap is rated at 15 so that is why its spitting out coolant. What can cause the pressure to build up so much, i don't think its a headgasket because i don't see any bubbles in the radiator.

 

I don't know, this is really just a guess. What kind of thermostat does the raptor use? Could it be stuck shut? If you don't think its a head gasket then you have ruled out my first choice. Does the red "idiot" light come on?

 

Well, once enough coolant blows out the light will come on. I was thinking about the thermostat, when i get a chance i'll drain the coolant and remove to check.

 

Your headgasket is screwed. Buy a HP headgasket and enjoy the ride.

 

Do you think if I pull the valve cover and retorque the head bolts it will seal, or is that a waste of time and i should just replace it.

 

I would just replace it with a hp. IMO you can retorgue but it will still leak at wide open throtle

 

I HAD THE SAME PROBLEM...replace the head gasket and all the bolts for the head, there are 6 total bolts that hold the head on....and 3 bolts that hold the valve cover on, but these three bolts go right thru the head and screw into the cylinder....my head gasket was leaking for the entire race season last year and when i pulled the head off....i saw exactly where is was leaking........get new gasket and bolts and becareful / **** when you torque the head down.....my head gasket is holding now and i just finished my first 2003 season opener in NEATV-MX.....placed 7th overall in the 30+ class....

herbdon out........