So, I went to national enduro this weekend, bike was running fine. During 1st section motor got noisy, and generally just sounded like ass. Pulled to side of trail, noticed cylinder was super hot, pulled the plug and it was white. Popped radiator cap. Dry. Nothing. Dang. So got to watch lotsa bikes zip by while I wait for sweep. there were lotsa lotsa gassers. and just a side note - whoever was on row 78 or so with a black honda crf250. dang you're fast. caught our whole row in 5 minutes. the other guys on my row said he caught them in every section quickly. and a thumbs up top the guy on the old tr5t! and the klr650
(he was a couple rows ahead of us, but we caught him in a minute or two..) it takes balls to do a national on either of those bikes...
Anyways, fast forward to now. Drained gearbox, oil looks fine. Pulled crankcase drain. Coolant poured out. Dang. So I'm assuming head o-ring failure. I'm assuming I get to replace: crank bearings, seals, con rod. I have a spare top end so that's going on it. It got really hot so I'm assuming the piston is toast. Theres some weeping coolant at the cylinder head joint near the front head mount. Maybe head cracked. I doubt both inner and outer o-rings failed (there's coolant in cyl and outside cyl).
Bummer.