Thanks Nick!
I ummed an arred for a while. Then decided to make a new
alloy piston, just to see what might happen.......

Realising there was 4mm spare space below the piston, I made the new one 3mm longer.
It stopped with a clunk, at the wear ridge made by the old piston!

So, I shortened it....... It still insisted on hitting the wear pattern!

So, I built the crank assembly, properly, while I thought about sleeving the cylinder........

The cylinder is 10mm bore, and the bottom of the fins is around 14mm dia.
So, I can only afford a cyl. with a wall thickness of1mm. I have ordered a length of cast iron.
Fraser.
Carbon! That's a great idea....... Until I priced some 3" x 1/2" dia. from Noggin. Hmmm.......
I think I'll try a cast iron piston, too!

David D