Hi Troops
Many thanks for the comments ... bit more...
Ran the thing continously for over two hours today. Not quite sure 'cos it was still going after two hours but was found stopped about an hour later.
Gas can had run out.
Anyway, stripped the engine to have a shufti, all was OK. Surprisingly.
Just a small mark on the PTFE piston about 2mm dia. and another small mark on the bore.
No idea why. Did not look like the piston had 'picked up' as I presume it would have left a longer smear on the bore ??
So, that's it. Basically it runs. Needs the odd snag rectifying, like the crankpins and some permanent screws in the structure.
Might even stick it on a wooden plinth and give it a lick of paint.

It does have one serious problem, it won't run until the power cylinder gets hot.
I assume it's because the hot air hits the cold metal and cools, thereby dropping pressure.
There is far, far too much metal in that power cylinder, but then, the whole idea was to use scrap bits ...
So, what's next ???
BC