First, take the mag back off and clamp the flange in a vise. Clamp a vice grip on the coupler bar to turn it over with. You should be able to get a spark from one of the wires. If not, then have the coil checked. After you get spark, this is the procedure for timing the mag. Timing a mag. (FMJ)
1. If you have taken the Mag. apart, the internal gears need to be timed. (Set points at .020)
2. Remove the large cap and line the C mark on the fiber gear with the marked tooth on the steel gear. Tip- turn the engine backwards to get the steel gear tooth to stop straight up and position the C mark on the fiber gear straight down. This times the rotor to the points. It is pretty simple in theory. Like all four cycles, the piston comes to TDC (top dead center) twice for every time the magneto or distributor rotor goes around. The left side of the engine has a hole in the bell housing where you can see the timing mark on the flywheel.("B"&"C") ("WD" &" WD45" The timing mark is found by looking under the flywheel housing for a small hole possibly covered by a small plate held with two wing bolts. The FIRE mark and the TDC mark are located on the flywheel through this hole. Use a little light colored paint to make seeing them much easier). 3. Take out the #1 spark plug, and put your thumb over the hole while hand cranking the engine(best to have all the plug wires off while doing this so the tractor doesn't try to fire) , the cylinder will force air past your finger on the compression stroke. (The other FIRE is the exhaust stroke and has the exhaust valves open so no air will come out of the plug hole).
4. When you feel the air coming past your thumb, look for the FIRE mark on the flywheel. When this mark is centered in the hole, the rotor on the mag should be just lower than the #1 lug on the mag. Looking at it as a clock, #1 lug should be near 10:00. Just before the lug is a plastic stud called the timing stud. Perfect timing is when the rotor points to the timing stud while the FIRE mark on the flywheel is centered in the hole. 5. If your rotor points to 5:00 your mag is 180 degrees off and needs to be removed and the coupling turned till you achieve 10:00. If it is not right on the timing stud, you can loosen the mag and rotate it until it is. 6. Put it all back together and time your spark plug wires 1-2-4-3 clockwise on the magneto cap.
Remember if the rotor is aligned with the timing lug when the fire mark is in the window, you got it right. If it's not quite aligned when the fire mark is in the hole, then you rotate the mag clockwise or counter clockwise until it is. Remember Perfect timing is when the rotor points to the timing stud while the FIRE mark on the flywheel is centered in the hole.
The magneto is a self generating ignition system. Inside there is an armature and field magnets just like a generator. The armature/field generates the low voltage required by the internal coil that steps up the voltage for the spark plugs. The coil, points and condenser and rotor are all inside the magneto and operate without any outside wires or voltage. The only wire required is to short out this system to stop the engine. The magneto also has an impulse start mechanism that stops the armature from turning momentarily and then clicks loudly when it lets go. This does two things. One it retards the spark so it does not kick back and two, when it lets go, the armature spins fast enough to generate the low voltage required for getting a spark when hand cranked very slow. Duey