blown base gasket

[yzexctxt]

just did a top end my 99 yz250, weisco piston, cometic gasket set, torqued to factory specs, and ran thru three heat cycles before riding the bike hard. after about half a tank of gas started smelling coolant, checked out the bike and noticed the base gasket pushed out below the exhaust manifold. are aftermarket gaskets cheap or could i have another problem, i even put a thin layer of yamabond on the base gasket like yamaha does. any thoughts would be appreciated.

 

[Durt Cycler]

Did you cross torque the 4 bolts? My best advise would be to strip down the topend and see. You might be able to fix the problem without fully taking the cylinder off the piston.

 

[DEANSFASTWAY]

You didnt go crazy with a diegrinder and wizzywheel did you / They can really distort the case ?cyl surfaces . I like to use YAMAHA base or ATHENA gasket kits they seem to be of better quality . COMETIC is good stuff though. Maybe the sealer helped the gasket slip out. This has happened to me before, try again . I would pull it all apart and start with another new gasket.

 

[yzexctxt]

took the cylinder off today, blew the gasket out from the water jacket and the gasket sucked into the crankcase on either side of the engine. maybe the yamabond allowed it to slip.

 

[Danny8785]

Was there any corrosion on the bolts? If there was you could have recieved a "false" torque reading. Just a thought