I got into the garage early this morning and did as Gadge suggested with regard to spinning the flywheel backwards. There was no bounce at all so compression does seem to be a problem, but I will still look at the carby.
I took the head off and was surprised to find some mouse sh!t under the head (but outside the cylinder). I turned the flywheel a few times and there was some movement in the inlet valve (or the valve I assume is the inlet valve) but nothing in from the exhaust valve. But after a few more revolutions there was some movement and after a few minutes both valves were opening and closing. As I mentioned at the outset, I am no mechanic, so would not mind an opinion on whether or not they are opening far enough (hopefully I can put up a video) and if there appears to be an issues with timing - it looks OK to me and I can think of no reason why anything would get out of sync, but always appreciate the opinion of someone who knows.
Any tips on how much cleaning the cylinder, valves and head require, and how to go about it, would also be appreciated.
