WR450 supermoto running hot

[Kyle_T]

2004 wr450 supermoto
Boyesen waterpump
Oversized radiators
50/50 coolant mix

Last summer I could ride all day in 90*F and keep the bike under 200*F.

Went for a ride tonight. Air temp was about 55*F. I'm cruising doing about 45mph. Notice my temp light come on and see the bike is at 200*F. Came to a stop, dropped back down a bit. Started going again, just cruising 40-45mph and the temp starts rising back to 200*F again. Headed home and the temp stayed right around 200 still.

After I parked it I check the bike over for any possible coolant leaks or anything. Didn't see anything. I didn't pop the radiator cap off yet because the bike is still hot but the coolant overflow is still half full. Could the waterpump have died? Why am I running so hot all of a sudden? Normally the bike wouldn't get over 170*F cruising in this weather.

[Borgschulze]

Either water pump or head gasket.

Start by draining coolant, and take the pump cover off, if the impeller is good, I'd probably pull the head and replace the head gasket next.

Is your coolant overflow usually mostly empty? Sounds like head gasket leaking combustion into the coolant passage causing it to throw up coolant and run hot.

[Kyle_T]

Ended up being the headgasket. I did a leakdown test yesterday and confirmed it.

[Borgschulze]

Well, good luck on the repair, hope it holds up.