Let's start at the beginning and work through again... The mag is in your hand and not on the tractor...
1. Put the Distributor cap on the mag. With a piece of chalk, mark where the location of the cap's #1 tower on the body of the mag. Remove the cap from the mag.
2. Rotate the mag drive (not the rotor, but the other end) backwards until the metal tang on the rotor matches up with the chalk mark you just made on the body of the mag. Put the mag down until a couple steps further along.
3. Take the #1 plug out of the head. With your finger over the plug hole, rotate the engine until you JUST BEGIN to feel pressure on your finger. Take your finger off the plug hole and go around so you can see the tractor's left side of the pulley where the pointer indicator is. Continue turning the engine until the pointer lines up with the SECOND notch if there are two notches in the pulley or the only notch if there is only one. You are now right at #1 piston on TDC. Don't crank anymore yet.
4. Walk around to the other side (tractor's right side) of the tractor and look in the housing where you are going to install the mag. Are the two notches at 8:00 and 2:00? if not, the governor is off time and should be corrected... If so, move on to the next step.
5. Grab the mag that you just moved in step 2. On the drive end, it should come close to lining up with the two notches in the governor. Install the mag without moving the drive any more than absolutely necessary. Since the cap is off the mag at this point, you should still see that the rotor is pointing near to the chalk mark you placed on the mag in step 2. Loosely place the bolt in the bottom slot to hold the mag in place, but not tightly. Install a grounding wire from the mag to a good ground on the tractor to dissipate any spark that is generated until it is time to start the tractor.
6. Rotate the square cap on top of the mag so it is as close to the engine block as you can possibly get it.
7. Walk around to the tractor's left side and using the crank rotate the engine one full revolution until the notch in the pulley lines up again with the pointer on the front cover. While doing this, you should only hear ONE snap in the mag...if you hear two snaps in that one rotation, there is something out of line with the governor.
8. Walk around to the mag side of the tractor. (right side) Slightly loosen the bottom bolt so you can rotate the mag. Here is the important part... Rotate the the mag so the square cap comes away from the engine block. Turn it slowly, slowly, slowly, until you just hear/feel a snap in the mag. It is now in time. Tighten the mag down.
9. Check your work by walking back to the left side of the tractor and cranking the engine with your crank through one full revolution. (timing mark back in line with the pointer). The mag should snap JUST as the timing mark comes in line with the pointer. Look at your mag again. (the cap is still off) The rotor should be pointing to your #1 tower location chalk mark.
10. Install the spark plug, cap and wires in their proper location. Install the lead from your mag switch from the dash, and try to start the tractor... it should fire well since it is now in time...
This is exactly how Donny taught me to do it when I first worked on Merlin (cub). I have since done this procedure many many times, and the tractor starts perfectly every time! Good luck!!!
Mike in La Crosse, WI