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
> 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.