The importance of polishing valves!

[Spider Wales]

I found no signs on the valve or valve seat of overheating, the clearances were checked by Steve Winterton, (all within spec, it was an interesting day spent with him and the thing certainly flew after he had had his grubbys on it!) about 3000 miles before I garaged it until it was pulled apart. I suspect as Thomas does, that it is a manufacturing fault that has been there for its life, fortunately it never let go. I have checked/cleaned up the others and apart from some corrosion on the combustion chamber faces, they seem serviceable, so I am realistically only looking for one 35mm Exhaust valve, new, or good condition second hand is the same to me. I will email around the usual suspects later.