Zephyr 750 holed piston

[Deleted]

Hi new to the forum,
just bought this 93' 750, with a hole in the piston, any idea's what caused the hole? i know it must have run lean, could the head gasket caused this, bent valve? carb mixture? timing out? at first look the cam and valves look okay, (will have them checked), slight scoring on the barrels no 3 +4, the camchain looked a bit slack but looked in time.

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[maxz1000]

A holed piston will almost certainly be due to a weak mixture of fuel caused by either an air leak at the carb rubbers or the carbs fouled or incorrectly adjusted.

You will obviously need oversized pistons and a rebore to get rid of the scoring, plus a carb rebuild. You may wish to decide whether it is worth it as you will not have much change from £1,000 even if you did it yourself.