444 leaking coolant when reved up?

Just turned my 2002 426 into a 444 but........ it wasn't doing it before, now when the bike is ridden it's blowing coolant out of the vent line by the cap. I replaced the rad cap thinking it was just week but it still does it. It's about a cup to a cup and a 1/2 in two hours of Ice Racing.

Any ideas?

Blown or leaking head gasket. The cylinder pressure is pressurizing the cooling system. Take your scooter to a radiator shop or motorcycle shop and have trhem pressure check the cooling system. Do it with the spark plug out and you should hear hissing coming from the cylinder. Been tere, done that...twice.

Birdy is right, its a leaking head gasket. When you replace the head gasket, use some copper coat gasket sealer (the spray on stuff).

Also be sure to "true up" the head and cylinder sealing surfaces, either by having a shop surface them or by taping a piece of 400 grit emory paper to a thick piece of glass and doing "figure eights" eith the sealing surfaces on te paper. Blue up the surfaces firts with layout fluid or machinist blue so you'll know when you're done...

I learned the hard way (had to do it twice, do it twice) how inportant this step is on the 426's...

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