Kawasaki Triples Club

Mitsui Spy wrote: ↑Wed Jun 14, 2023 8:45 pm Well, I'm can't say categorically it was the head gasket but that's the only conclusion I could draw. It had nipped up previously but the inlet stubs were very worn and the carbs were pretty loose. I renovated the inlets and gave the bore a bit of a hone. Rebuilt it with new gaskets, took it for a short run the next day then retorqued the head bolts. Did 50 miles at 60 -70 on the motorway then suddenly out of the blue ..."BLOOOOOR!" . Coasted to the hard shoulder, let her cool down, tried to start her but sounded very sick. Limped a mile or two to the nearest exit and pulled the top end off. The head bolts were not much more than finger tight! The front edge of the piston was totally melted through.

What I think happened was, the base gasket relaxed over the first 50 miles until the head gasket lost its seal. Big in-rush of air instantly melted the piston. Never heard it coming. I believe my short run in the morning (a couple of miles to the petrol station) didn't provide enough heat to settle the gaskets so I had re-torqued them before they'd fully relaxed. With seizures there's always a tad of doubt floating around but that's my theory for what happened to me.

I've run bikes with weeping head gaskets before and it's not been an issue, clearly it depends on the type of leak. A bit of oily residue getting forced out under very high combustion pressure is most likely fine, but when a head gasket is so far gone it lets air be drawn in under relatively low pressure it's a very different matter. Was your head still fully tight Gary?