Petrol Mower - stuck valve?

You might try removing the spark plug, and spraying oil in, before warming to 100C or so with a blow-heater.

Could also be a broken valve spring. All these types of engine are a piece of piss to strip down. Just get stuck in and take photos along the way to help you put it back together again.

Dave Baker - Puma Race Engines

Could be a similar engine (possibly even the same) as the Briggs and Stratton that I took apart last summer on my old Webb mower. Symptoms were the same as yours: no compression at all. I had done a few DIY jobs on cars over the years, including some semi complex stuff, but this was the first time I had fully taken to pieces an engine. It turned out to be an absolute doddle. The problem was pretty obvious when I got it apart: the exhaust valve seat insert had come out of the recess where it was supposed to sit and was just flapping around (and preventing the valve closing properly). I cleaned the seat with a wire brush, smeared some exhaust sealant paste on the seat and insert, shoved the thing back into place and heated with a paint stripper to cure the gobbo. Runs just fine now, although time will tell....

Regards, Jim.

Many thanks, Jim - that's the sort of answer that we all are hoping for when posting a query. I'll get stuck in shortly - hope you won't mind but if I run into any problems I'll get in contact.

Rob