You've got a good point Chris, as it was definitely detonation rather than a hot seizure. Piston crown looks brown/grey rather than black though.
Carb recently rebuilt. 1.5 turns on low jet, 1/8 turn on high jet. Engine on about 5 hours, although piston has done more like 15 as I didn't change it last rebuild. B9EGV plug and unleaded rather than super unleaded fuel might be some of the problem, but it did all look on the lean side when I stripped it.
Detonated next to the exhaust port, so the edge of the piston crown down to the ring land broke off. Fortunately the bore and head haven't picked up any damage worth noting...
Any thoughts on fuel and plugs? It wasn't a very hot day, but maybe a 10 might be the thing to use.
Liam
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