Hi Rbob, thanks for your detailed reply.

I stripped it down yesty arvy and it wasn't pretty. A section of the top ring is completely stuck.

There doesn't seem to be any play in the crank bearing, just a smidgen in the big end.

Here are some pics of the piston and barrel,

[Linked Image from i3.photobucket.com]

[Linked Image from i3.photobucket.com]

The guy said it wasn't working due to carb issues but he could have admitted he straight fuelled it.