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You say the tabs on the rotor keep burning. When you say "tabs" it HINTS that you have a Wico type X mag. By burning, do you mean they are charring the plastic to the point of damage or are they just accumuating a bit of black ash on the surface of the rotor arms & the cap buttons? The black ash is rather normal. The reason I ask is that for serious damage to occur here (burning of the metal and or the plastic) indicates the spark is jumping a WIDE gap between the rotor and the cap's posts or buttons. To do this however means that the spark is happening at the wrong time WITHIN the mag. This spark timing (the mag's internal timing) has nothing to do with how the mag is installed on the tractor or how the engine is timed and may indicate something wrong inside the mag. If you have burning of the cap and the rotor's arms taking place, check the points gap! Correct point gap is even more critical on a mag than on an electric distributor! The Wico mags (both C and X) should be set at .015". Make sure your shaft bearings are in good condition & that the mag's shaft is not loose or wobbling in the case. Also make sure that your rotor is properly installed (check for the metal spring inside the rotor) on the magneto's shaft. If the problem is not here, it's probably best to post back with exactly which mag you have on your tractor and more clarification on the burning you mention. We can help you with setting the run timing but need to know what mag you have first. With the exception of the burning, what you describe sounds like it's running too far advanced. If too far advanced on the run timing, once the load gets to a certain point, they'll quit like a key was shut off especially if the compression has been raised very far above original. Seems nothing you do will help it recover either. Choking it seems to have no effect. Removing the load and quickly returning the throttle to slow idle seems to have the best chance of letting it recover. Otherwise, it's simply going to die! On a Wico X as you look at the impulse drive coupling, a quick rough check of run timing is the timing mark on the impulse ring (the ring behind the drive coupling held fast by 4 slotted screws) 2 and a half marks left of the long mark on the mag case. If yours is setting 4 or 5 marks left (not uncommon) it is too far advanced. Move it to 2.5 & try that. Hope this helps.
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