Blown Head Cover Gasket

A friend of my blew out the head cover gasket on his '02 426. He said he just cleaned up the bike, changed the oil and air cleaner and then when out for a ride. Not more than 10 minutes into the ride the gasket blew out on the left side. Has anyone heard of this before? I asked if the vent tube was clear and he said it was. Could that do it? He said the gasket didn't look hurt and could probably just reinstall in, but I would really want to know why this happened first. Any insight would be greatly appreciated.

Thank you.

Dirtorpedo,

Usually when the valve cover gasket blows out it is caused by a broken piston. Pressure builds up in the crankcase from compression and it pops out. Have your friend do a leak down test before he rides again. That shold tell you whats going on.

Thanks, Brian, for the reply. I found out that in fact that the vent hose was pinched off at the lower bracket. A rock must have smashed the bracket enough to pinch the hose. They put it back together and everything seems to be just fine, it runs great.

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