Just taken the top end apart after 13000 miles, on my 1980 TR7. The exhaust valves have clearly been running red hot, judging by their dark blue colour. They were still seating well (the seats had also gone quite blue). Valves were good quality (G&S). So, that's my first question really - is it normal for exhaust valves to run as hot as this and if not, what conditions might be the cause? The mixture shouldn't be weak - carb jetting is way richer than standard (straight through 2-into-1, no silencer). Ignition timing was OK when I fitted the third Trispark unit about 3000 miles ago, and nothing has moved since (though I thought it was sounding a bit retarded the last few times I rode it - one of the symptoms of a Trispark about to pack up!). The head has some kind of aftermarket exhaust stubs, meant to convert push-in to push-over pipes. They are fairly thick aluminium - more than double the thickness of the genuine screwed-in steel stubs. I wonder whether these could have been restricting exhaust gas flow to the point where heat was building up excessively? The combustion chamber squish bands were in a strange state, looking as f they'd been roughly shot blasted. They looked as if the aluminium had become so hot it had been close to melting, leaving a 'ridge' around the upper edge of the squish band of roughly .5mm (maybe 1mm in the worst places) that you can feel very easily with a fingertip. The pistons seem ok though, and if this kind of heat had been accumulating, wouldn't the expectation be for the pistons to suffer? Any thoughts would be welcome. I have some photos but not sure how to put them on here?