Most tractor mags fire at or very near TDC while the impulse is engaged (cranking), then advance all at once to about 25� BTDC (the exact "spec", "lag angle" is specified by the engine manufacturer).
So, the flywheel timing mark is likely to be @ TDC.
You CAN'T advance the mag earlier than that or the engine will "kick", destroying the starter (which could be YOU)!
So, if the mag fires @ about TDC @ cranking, and the actual running timing is not "early" enough, you CAN'T advance the mag, but will have to rebuild the impulse and/or switch it to a unit with a greater "lag angle".
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Today's Featured Article - A 1937 John Deere Unstuck - by Gary Hickman. Here is my story of how I got the pistons out of a 1937 JD B that the engine had been stuck for about 14 years: About 12 years ago my Dad gave me one of the tractors I ran as I was growing up on our farm in central Nebraska. The engine on this tractor, a 1937 John Deere "B", had been stuck for 2 years before he gave it to me. This last spring (1999) I hauled the tractor to our 2 acre lot in St. Libory Nebraska where it joined my antique machinery collection, at that time a 1929 Caterpillar T
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