Prov 200 burned no1 piston

[slsail]

Was running at 5000rpm when I lost power .
I shut down.
When i came home I pulled the head to find a melted no 1 piston.
Everything looks good no water in oil. carbs look good.
I did find my oil pump linkage (the plastic part) cracked. So the pump lever was not in the correct full throttle position maybe 3/16 inch.
Only No 1 shows any damage.

Burnt #1 piston in Yamaha 2stk 90hp

I had a similar experience, number 1 piston melted at exhaust port, no apparent reason, oil injection looks ok, as does carb, Not sure what caused melt down, ran at under 4k always.