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Message: [QUOTE="jescombe, post: 322340, member: 28670"] I took my 453cc YZF Supermoto to the track today - all is not well :( I've just put it all back together after raising the compression from 11.5:1 to 12.5:1. I had the piston crown machined down to reduce the depth, re-profiled to retain the original squish band width, the valve pockets re-cut, and the barrel decked to retain .040" of squish clearance. I also radiused the edges of the valve pockets and generally cleaned up any sharp edges.. When putting it back together, I degreed the cams to bring them back to spec. So essentially, it looks much like before, just with less depth in the piston crown. Anyhow, out on the track, it would only manage a couple of fast laps before starting to churn coolant out of the radiator overflow (fortunately into a catch tank).. I'm thinking that its either running way too hot, or has a blown head gasket..? It doesn't seem to be pressurising the coolant when revved hard on the stand, so I'm leaning towards boiling over under load. Any suggestions on what I can do to make it run cooler? Would switching from pump (97RON) to race gas help? Atol fuels seem to be the standard choice in the UK, [url]http://www.atolfuel.co.uk/competition_fuels.asp[/url] has links to the specs for their products. Is raising the boiling point with a higher pressure radiator cap sensible - or just masking the problem? Thanks in advance, Jon E. [/QUOTE]