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Clooney
05-14-2002 03:39:25
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Re: JD 420S Idle and Load problems in reply to Bill Gangwer, 05-13-2002 20:32:29
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Bill, without knowing more specifics it sounds like you could still have a carb problem. But other things could also cause the same problem.
~That intermittent miss at idle is not really normal for a 420 but does appear occasionally on engines with some wear & time on them,
~Install a fresh set of plugs [again], once the plugs foul a little they don't self clean worth a darn on the 40-420. Try a set of H-12 & if only playing with the tractor, use 2 gaskets under each plug [set the plug gap to .028"].
~You could also have worn distributor bushings [that is common on the 40-420] try setting the point gap about .005" wider than you have now.
~Make sure the plug wires are solid core, [NOT automotive TVRS type with carbon centers] ~Try running with the air cleaner disconnected [those air cleaners will plug from years of dirt & can restrict air flow] if that makes a difference, remove & boil out the air cleaner canister.
~Adjust the carb for best idle warm, & adjust the load needle under LOAD, not just a fast idle. If you don�t have a way of loading it, either pull a loaded trailer, another tractor or go climb a hill in high gear. To properly adjust the �load needle� [key word load] turn the load needle in until the engine just starts to pop & run bad then slowly open the load needle until it just starts to run good, then open it another � turn.
~If after checking the above, you still have problems suspect a carb problem, worn valve guides, leaking valves [run a compression check] , worn cam [hard to test for], worn distributor bushings [remove the dist & wobble the shaft around to see how much bushing play], or the possibility of an intake manifold leak [close both intake valves then remove the carb & use your air compressor to put about 20 lbs of air pressure in the manifold & see where it comes out]
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