allis b magneto timeing

I assume you are talking about an FMJ magneto which was common on the B. There are two gears under that main cover that have to be meshed correctly. The steel drive gear should have one of the teeth marked with a chamfer. There should be two marks on the fiber driven gear, an A and a C. They may be hard to see. Do not use a solvent for cleaning as you could wipe the marks off. The gears need to mesh such that the C mark lines up with the chamfered tooth. See this description. This is most easily done with the mag off the tractor. There are two ways to time the mag to the tractor that are explaned here. If you don't wish to remove the mag, try the following:
1. Rotate the engine to top dead center for #1 piston - the "CENTER" mark on the flywheel will show in the timing opening. Be sure the piston is on the compression stroke. The mag should have just snapped at that point. If not, rotate the engine a slight amount more in the normal direction until the mag snaps. 2. Rotate the engine backwards (from normal rotation) until the "FIRE" mark on the flywheel shows in the timing opening. This will be about 30 crank degrees before TDC for #1 piston.
3. Rotate the rotor assembly in the main cover such that the rotor contact lines up with the timing boss. See the diagram in the second link above.
4. Assemble the main cover to the mag being careful not to move the rotor assembly.

Rod