Just an update on where I'm at. I have changed the o-ring under the starter, the head gasket and tracked down some piston rings but they were taken out of another machine, the guy at the mower shop assured me that they'd be fine. So having done all this, the machine still does not fire up although the compression is very strong and noticeable.
What is troubling though is that when you pull on the starter, smoke appears, it appears to be coming from the decompressor area. Whipped off the muffler, can't see any piston damage but the smoke worries me, any ideas what's gone wrong?
Should add that I squirted a little petrol in the spark plug hole to see if it would start.

Last edited by tiger; 01/01/13 01:55 PM.