On Fri, 30 Apr 2010 13:19:10 +0000, Jules Richardson wrote:
The engine's a 10HP B+S with electric start. Fresh gas, fresh oil. Fuel
line's clear, carb is free of debris. It's got compression, spark, and
is getting gas to the cylinder. I pulled the head and checked the bore
and valve seats, and no obvious problems there.

I'm wondering about the compression, now. Can low compression result in
an engine that won't even start/run under no load?

It's got some compression for sure (nice healthy hiss from the crankcase
breather on the down-stroke if I turn by hand), but I tore into the 11HP
engine from the donor mower I picked up at the weekend, and that engine's
piston fits *far* more snugly in the bore than on the 10HP. It slides
well (so no apparent issue with ears of it sitting there unusued), but
fits better with no detectable side-to-side movement if I try wobbling
it, unlike the 10HP.

(Although if it is a compression issue, I still don't get why it was
running last season and magically broke over the winter...)

Oh, I cleaned up the carb on the 11HP and tried it on the 10HP. It will
fire consistantly for maybe 4-5revs, then die, so not really any better
than the 10HP's own carb was. No different swapping the plug, either.
Magneto is unfortunately trashed on the 11HP, so I can't try swapping
that.

cheers

Jules