If you would give a bit more information on what you've tried so far that hasn't worked, your chances of getting useful feedback would go up considerably. What plugs are you using now, and which have you tried in the past? Have you removed a plug and looked at the spark to see if it's weak? Have you tried to operate it without the air cleaner hose attached? Is the choke plate operating properly; especially, is it opening all the way? Does the air intake to the carb. look wet. If so, under what conditions? Does the tractor appear to operate differently with the air cleaner connected (if so, it may be partially plugged - not a bad idea to pull it off, fill it with kerosene or diesel to clean its screen, and drain it good before reinstalling it in any case - supposed to be done periodically, but probably hasn't been since the tractor was new). How far off their respective seats are your adjustment screws on the carb. set? Have you REALLY tried to move these as close to closed as the tractor will tolerate and still run? These control the fuel/air ratio, and are the most "obvious" source of too rich a mixture. Have you looked for leakage around the intake manifold? Unlikely, but a leak here could necessitate overly rich adjustment at the carb. and result in fouling at the plugs. Have you checked the timing and the valve lash lately? Might be most anything on this list, which hopefully is helpful - let us know how you make out.
|