magneto timing

There should be timing marks on the governor gear too. They must be lined up with the cam to time the mag. The drive lugs will then be where they are supposed to be. Not necessary to be horizontal. If you snap the grounded mag by hand with a plug wire and grounded spark plug it should fire the plug on 1 of the 4 snaps

When cylinder number one is at TDC on compression stroke is when the impulse spark needs to happen on startup.  All magnetos that came on the WC fired on the horizontal like all standard Fairbanks-Morse mags.  You can easily test your mag if it is off the tractor, turn the impulse coupler by hand and look where it is when it is ready to snap - if it is a regular mag it will be horizontal.  The easiest way I have found to know you have the number one cylinder at TDC is by looking at the crankshaft pulley, the set-screw on the pulley points straight down on the WC (it points up on the RC).  So with the spark plugs out you can feel with a thumb in the spark plug hole of number one when air is being pushed out as the hand crank is slowly turned, this is the compression stroke.  Then just slowly continue turning with the hand crank until the crankshaft pulley set screw points straight down and you are at TDC.  This is when the spark from impulse needs to occur so the mag coupling has to be horizontal with the crankshaft in this position.