While not related to cars, thought I would post this oddity just in case someone else suffers the same problem with a lawn tractor. The Briggs 17.5 Horse in mine had quickly gotten balky about starting. The symptoms were similar to:
Bad starter motor.
Hydrolocked engine. (Engine very balky about rotating through the compression stroke even by hand.)
Battery tested fine and it took about 3 minutes to remove and disassemble the starter motor. Nothing wrong there with any of it.
A local starter/alternator shop owner told me that several people had been in with similar complaints and it was caused by the valves but he wasn’t sure on that aspect of it.
So removal of the valve cover and a check showed both intake and exhaust valves had about .010 clearance. I readjusted both to about .005 and problem solved. Turns over like a new one and fires right up every time.
I can understand the premise of cam lobe duration/overlap in an effort to create a compression release but the measly .005 of an inch making all of the difference in the world kind of surprises me.
Something to keep in mind if mower motor decides to get cranky; or non-cranky as the case may be.