Had a great day out at Ducks Nuts Ride Park 2 hours out of Perth. Went with a mate who has a CR500. I took both my YZ125K's. Run the yellow one in with its new ProX piston. However, after about 30-40 minutes on each bike, they both blew white smoke and died. Still kicking over but no life. I pulled the plugs and both had antifreeze on the plugs.
A couple of things... i used a torque wrench to torque up the yellow bikes head (18ft/pounds 25nm).. but it never felt very tight. The white bike had a lot tighter head nuts using a 12mm spanner "hand tight".. both done in a crisscross pattern.
The white bike had the rad cap swapped out for a 1.6 bar one, as i was loosing fluid through the overflow.
Both bikes use after market Mitaka head gaskets.
Just wondering if you guys have any idea's on what can cause the problem with both bikes. Does anyone use yamabond either side of the head gasket.. could the head studs be stretching, cap holding too much pressure, bad quality head gaskets, head not tight enough, any other things??
Will order a few OEM head gaskets anyway, but i also have a few more new Mitaka head gaskets.
I haven't pulled the heads off yet, as we only went riding today.. is there anything i should look for?
Did some research tonight and Wiseco do produce a 58mm head gasket. Have put 3 hours on this top end without a problem, but perhaps with the higher pressure cap, something has let go. Will also order the W4053 gasket kit.
One other thing... the white bike has a 2mm oversize piston. Have been using a stock size head gasket.
Cheers guys...
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