Mower with a Briggs & Stratton Engine Won't Start

I'm working on a 12Hp Briggs which powers a ride on mower. It won't start and a compression test revealed it had only 7psi dry and 10psi wet. I've stripped the engine bare and can't find a single thing wrong with it. The engine has completed perhaps 100 hrs. Everything inside the engine is as it should be. It has electric start, so I would have expected more than this small amount. Has anyone any idea what the compression pressure should be?

David from England, UK

Answers:

Mower with a Briggs & Stratton Engine Won't Start

The Briggs with next to no compression, we found the fault in the end. Careful (very careful) inspection of the cylinder head revealed a burn mark where gas had been leaking past the gasket. Obviously very little was leaking past but on reassembly of the engine, cleaning the carb, changing the fuel and basically doing everything we could think of, she starts and runs fine. Hopefully this info will help some of you other guys out there with similar problems.
(04/25/2008)

By David Waters

Mower with a Briggs & Stratton Engine Won't Start

Should be around 60-80psi. (06/01/2008)

By Chris