I left town after my post. The tractor runs great at wide open
throttle. What is strange the surging goes away when the mowing deck
is engaged no matter the trottle or even choke setting. I'll adjust
the idle screw for mixture too eliminate the surging at low trottle
and open choke so I can putz around the yard pulling a small yard
trailer. If you ever have to decide get the hydrostatic automatic
transmission so you can literally creep.

Thanks,
Jim


"Patch" wrote in message ...
"Space Cowboy" wrote in message
om...
Hi all,

I have a 20hp MtD Lawn Machine Riding tractor and my elevation is 6000
ft. I pull the choke(close) and its starts on the first or second
crank. When I push the choke(open) after warming up I get a surging
rough idle. If I pull the choke about a quarter closed the rough idle
goes away and the engine sounds fine. Is this normal operation for a
tractor at elevation ie enriched fuel mixture?

Thanks,
Jim

Yes, what you need to do is adjust the air\fuel mixture so it runs smoothly
with the choke in fully.