Magneto timing

I have a 1954 Farmall Super C tractor with an H-4 magneto that originally was on my Farmall M. I had to replace the coil in it several years ago when I mounted it on the Super C, and it seemed to run fine, but I couldn't time it properly. Yesterday I replaced the points, capaciter, and rotor in it and still have the timing problem. When I turn the engine over to Top Dead Center mark on cylinder number one, and I try to rotate the magneto to the point where the impulse coupler fires, I hit the limits of movement before I get there. So my magneto is turned so the top is away from the engine block all the way to the limit. If I start cranking the engine, the impulse coupler fires just maybe 5 degrees away from Top Dead Center. Is there a way to fix this so the Top Dead Center position occurs somewhere in the middle of the ajustment range when the impulse coupler fires? Or should I be timing it some other way?

Just a guess but sounds like the rotor timing is off by one tooth.

Pull the governor housing & move the gear one notch in the direction that will correct it. Sounds like it is too far retarded.

Do not move that gear but you will need to move the gear that drives the rotor when you replaced the points you probably got the rotor out of time with the cap. Make a mark with a marker where #1 wire goes to the plug. Then if you remove the cap and watch the rotor snap you will see the rotor move then stop at that tower when it fires. I am asuming that you didnt move the gear that drives the mag when you removed it as it does need to be lined up on the punch marks so it is in time with the valve trainect. Those marks are on the front and to see them you do need to remove the gov assy to check.From your description it sounds like the rotor is only off a tooth.

If you have never been able to time the magneto since the change over, the problem is probably the governor gear off time.

Changing the rotor timing inside the magneto will have no effect on when the impulse snaps.

Unless I misunderstood what he was saying, he carried the problem from M to the C then it’s internal.

5° after TDC? That should be fine.

If you mean impulse trips about 5 degrees after top dead center, that is very good. If before, very bad and you will have to move drive gear a cog. Changing the rotor will have zero effect on the impulse. Heck, throw the rotor assembly aside and the impulse will still do what it does.

Sure the impulse is fine but the rotor needs to be lined up to the tower when it trips.

He's talking impulse timing, we all know the rotor has to be timed internally but that is not the point of this discussion.

Rotor timing has nothing to do with when the impulse snaps & that is what is not right in his case.

Don, for the H4 application, there are only 2 positions that the mag drive can be in, the correct one, and 180 degrees out of time. If your timing is wrong, there are 2 places to check. One is the mag drive gear in the govenor. I spent 2 weeks scratching my head on an A that I converted back to mag from battery ignition. For the life of me, I couldn't figure out why it was out of time. Well, the PO didn't line up the timing marks on the governer gear when he rebuilt it. That is NOT an issue so much with a battery ignition, because you have unlimited timing adjustment by rotating the distributor. On a mag, you do NOT have the luxury. Anyway, took the govenor off and got the timing marks lined up and it worked like a champ.

Now, the other place you can get an H4 mag out of time is internal to the mag. The rotor MUST be timed correctly to the mag shaft. There are timing marks that must be in correct orientation. If you pulled the rotor cover off to replace the points, make sure you got it correctly oriented (timed).

Lastly, I agree with previous post, the internal mag timing has NOTHING to do with when the impulse trips.

I hope this helps a bit. if all else fails, send me a note, and I will be happy to provide my phone number to talk you through any of this. email shold be open.

I thank everybody for their help. The tractor (Farmall Super C) originally had a regular coil type ignition on it and I could always time it without any problems. And I also have a Farmall M that originally had this magneto on it, which I could time properly. But the magneto coil burned out, and I had to move the Farmall M to a new place we were moving to, so I borrowed the electric ignition off the Super C and put it on the M and it runs good. Later, in order to get the Super C running again, I replaced the coil in the magneto and mounted it on the Super C. And left it there because then, if the battery went dead, I could crank start that, but I could never crank start the M. After mounting the magneto on ths Super C, it always was slightly out of time, and I had checked the timing marks in the gears in the magneto. So, I have come to the conclusion from this discussion that the drive gears in the governor are probably off one tooth. And always have been from the factory. So, I will have to look at taking the cover off the governor and see what I can do. Is it a long and tough job and do I need various seals and gaskets to do this? Or do I need to be a professional mechanic?

Don, took me about 1 1/2 hours start to finish. It is not that difficult, and the timing marks are fairly visible with my "cheater" glasses and a small flashlight. Biggest issue I had is that I left the rad on and had to fit my big ham hands in the tight quarters.

Once the mag drive gears are timed, just make sure that #1 cylinder is on TDC, then place the mag on. Pretty much it. Like I said before, with the H4 mag, you can only be in 1 of 2 timing locations........dead on or 180 degrees out.

There are a few degrees of adjustment on the mag, which if you roll it as far as it will go "away" from the block, while on tdc, then slowly roll towards the block, the impulse should trip. Back up 1-2 degrees, and tighten her down. If you ever plan to crank the old girl, that should be exactly where you need to be.

Once again, feel free to call me. Send a PM or email for my phone number.

Thanks for your offer to help. I would like to go out to the tractor in the barn and call you with my cell phone. But I don't know what a PM is or how to do it. And I don't know how to get your email address Tom.

email addres is flemingt at consolidated dot net

cell phone is four one two
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