I know this is a little OT, but there seem to be a lot of
knowledgeable small engine people in the group. My riding mower with
a Tecumsah engine has been giving me a lot of problems, quiting, rough
running and loss of power. I cleaned air filter, changed plug, and
checked fuel filter. I found I could get it to run by using choke,
increasing the choke level as fuel level in tank went down. So it
seemed to be running very lean.

Day before yesterday, I was mowing when I smelled smoke. I looked
around at my and neighboring houses- no smoke. I looked over to a
nearby wetland- no smoke. After awhile a light dawned in my brain and
I looked behind me at back of mower- smoke pouring out. It was coming
from around rear axle. I got out garden hose and wet down rear axle
area. There was a lot of grass piled up on top of rear axle, and also
mower deck, but not around engine. I had been keeping that area pretty
clean.

After cleaning away all the old grass around rear and mower deck I
restarted engine. I apparently overchoked it and it was hard to start,
but got it started with only slight choke. Then I found I could put
choke all the way in, and it runs fine. Good power is back. Glad to
have it running well, but the problem puzzles me.

So, what could happen in rear axle area or on motor deck with
collection of grass that would cause a front mounted engine to run
lean? Sure, the grass clippings could have put more drag on mower
deck or axle drive, but why would richening the mixture greatly
improve power. I would think that any mixture change away from the
normal mixture setting, when the engine was at operating temp, would
REDUCE power, not increase it.

BTW, I had previously ran two tankfuls through with a carb cleaner.