Piston skirt to cylinder wall clearance

[BSA_54A10]

If this bike is purely for your own use and not for resale then you can get the thrust faces knurled,shot blasted, center punched or have the entire piston expanded.
Back when labour was cheap and parts were expensive we used to get our racing pistons either knurled or expanded between every 3rd or 4th meeting.
To go with the excessive cleareces we also used oversized rings (correct bore diameter but bigger radial depth) and we raced ( well they actually I only ever warmed the motor up enough to change from starting plugs to the racing plugs ) . Now this was a metho drinker running at near 15:1 by the time we retired it.
So there are a few alertnatives if it is just a week end plodder.

[Triton Thrasher]

HI Bill,
Yes its to do with the ovality thats manufactured into the piston design..................................

Thanks John, guess working in my shed amongst 50 year old stuff leaves the modern world and methods behind sometimes

Pistons have been oval for a lot longer than 50 years.

[bsa-bill]

Pistons have been oval for a lot longer than 50 years.

I know that but was not sure where the ovalitiy occurred

Thanks John, guess working in my shed amongst 50 year old stuff leaves the modern world and methods behind sometimes

was referring to computer aided manufacturing methods which I probably also knew at some point in time but had forgot about