On Wed, 05 May 2010 14:50:08 -0700, Oren wrote:

On Wed, 5 May 2010 17:53:42 +0000 (UTC), Jules Richardson
wrote:

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

One of the piston rings froze up?

Yep, I thought the same thing.

OR A valve is sticking open.

Before ripping it all apart, pour some kerosene or diesel in the
sparkplug hole. (bout a quarter cup) Put the plug back in finger
tight, without the plug wire attached. Turn the engine over by hand.
It will likely not turn all the way because of fluid lock when the
piston comes to the top. Leave it sit like that for a day. If a ring
is stuck, this may free it, as well as a stuck valve. You can always
open a cover on most engines to see the valve stems move. You can
always work them up and down with a plyers.

When you want to start it, remove the spark plug and spin it over to
blow out the remaining kerosene, clean the plug and reinstall it, and
try to start the engine.

Once you get it started, change the oil because the kerosene may have
diluted it.

If the kerosene is gone after one day, you definately have a leaking
piston ring.

--

I just reread your original message. Since you have the head off,
lower the piston and pour some kerosene on it. Work it up and down by
hand and leave it sit with the kero in the cylinder for a day.

YOU WROTE
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.

Did you know that you can take a propane torch, turn it on, (dont
light it), and let the propane enter the carburetor while it's
running. It should stay running because the propane is burning in the
engine. If it's the magneto, it still wont run. If the carb is at
fault, it should still run from the propane.