On top of the engine is a big flywheel. When you hit a stump
or other hard object, the flywheel turns in relation to the
crank shaft. That shears off the flywheel key. I can walk
you through the repair, if you wish. I also used to have a
bunch of flywheel keys, for B and S. Not sure they use the
same ones, now days.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Zootal" wrote in message
7.131...
I have a Craftsman mower, 6hp, B&S overhead valve engine.
This engine has
always started on the first or second pull. Open throttle,
close the manual
choke, give one or two lazy pulls and it fires right up. It
is the easiest
starting mower I have ever had!

I ran over a stump that stuck up a few inches - it was in
tall grass, I
didn't see it, and the blade hit it hard, immediately
stopping the engine.
Thunk, engine stopped. The plastic cover over the pull
starter popped off,
it hit so hard.

Now the engine won't start. It pops and sputters and
backfires out the
carb, but absolutely will not start. Thinking a timing gear
(or whatever
valve timing mechanism it has) had skipped a gear/notch, I
pulled the valve
cover, pulled the spark plug, and watched to see if the
rockers arms would
both rock at TDC, and as far as I can tell they do, though
I'm not sure how
accurate or reliable of a test that is.

The engine turns over easily, but it always has - if
anything it turns over
easier than it should, which is what made me think the valve
timing was
off, though it's hard to tell.

Anyone have enough experience with this engine or type of
engine to comment
on what might have happened, and availability/cost of parts
should I decide
to tear the engine down? I don't know if sheared a key,
skipped a
tooth/cog, bent a valve in the process or what I'll find
when I tear it
open. It's been a good mower, and it's worth a bit of time
and effort to me
to fix it.