39 Allis B

Does anyone have a copy of the
manual that details how to time a
magneto? Thanks

Is the magneto on the tractor or do you have it off?

Still on. Just trying to collect info in case I have to take this motor apart.

The way I do it is to make sure both rocker arms are up. (both valves closed) on number one when the impulse snaps turning slow that the TDC or CENTER line is in the center of the inspection hole.

If the magneto is off and your are mounting it you would make sure the magneto is ready to fire number one and bring the number one up on the compression stroke until the FIRE line is in the inspection hole. Most will check for the compression stroke with their thumb on the spark plug hole. With my crippled hands I use the rocker arm position to check for both valves to closing. The reason for using the Fire line is because the impulse spring is not loaded ready to fire. Actually when I have the FIRE line in the inspection hole I back it up some to remove all tension on the impulse spring to make it easier to line up the drive dogs.

You most likely already know this deal I did for another Allis newbie



----------------------------------------------------------------------------------------------------It is really easy with the valve cover off while adjusting the valves. If your magneto is hot and throws a spark, with both rocker arms up the instant the impulse snaps the TDC or some CENTER line is in the center of the inspection hole it is in time. If it is not in the center of the inspection hole the magneto can be rotated to place the line in the hole.

There is several other ways people get it in time but this is the fastest way.

All four cycle engines static time at top dead center. When the timing mark is in the center of the inspection hole one of the pistons is at top dead center. When both rocker arms are up on a cylinder it tells you which cylinder is at top dead center and ready to fire that cylinder. You will want this to happen on number one normally. How ever if it is sending spark to the cylinder that is on top dead center with both rocker arms up it would still be in time. That either confuses some or makes the process easier to understand.

When your engine has the TDC line in the center of the inspection hole two pistons are at TDC. One is on the compression stroke and the other is on the exhaust stroke. One more revolution to TDC sends the other two pistons to TDC with the same conditions. The next revolution sends the first two pistons to TDC with the opposite piston on the compression stroke with the other rocker arms up.

When the TDC is in the center of the inspection hole that will also be where you want to set the valve clearance on the cylinder that both rocker arms are up.

This is also not the only to set valve clearance but doing it this way while learning will etch how the camshaft operates the rockers to open the vales in time.

My 40 B does not have a TDC mark, it only has a "Fire" mark which is ?30? BEFORE TDC.

The procure that is in the Allis (and I&T) manual (which also assumes the governor gear was timed correctly based on the marks on the camshaft). Also this if for an FMJ mag that is properly timed internally:

1. Remove the distributor cover, and in the upper left corner there should be 2 raised bars label 4 and 6 (for number of cylinders).
2. Rotate the mag BACKWARDS until the rotor is inline with the "4" lug
3. Rotate the engine over until it is on the compression cycle in the first cylinder and line up the "FIRE" mark through the right inspection hole (right as seated on the tractor)
4. The mag lugs SHOULD now line up with the drive on the governor gear.
5. Bolt the mag up and fine tune the adjustment to get the rotor back to point at the "4" lug.
6. The upper left spark plug hole is #1, upper right is #2, lower right is #4, and lower left is #3
7. I would pull start it the first time before trying to crank it by hand. If it backfire instead of starts you are probably 180 degrees out of time

Once I re-timed my B to the above procedure, I have never had an issue with the crank "kicking back" when trying to hand start it (It previously would kick back occasionally). My WC also was timed this way and also does not kick back when hand cranking (It backfired pretty bad when I was 180 out of time...)

If you are going to try hand cranking, go search the forums for proper tips, the main one being keep your thumbs on the same side as your fingers (don't grip the crank)

One thing that would help them help you is telling them what mag it has. I do have hard copies of the mag manual I us to send to people so if some one does not come up with one for you let me know and I can get a copy and send it to you snail mail