Magneto/ Any all other thoughts welcome

Thanks Den MS maybe someone will need this and it will be in the archives for other 2N owners I got it to fire on 1 and its in the #1 hole and #1 on the cap.Runs great.
FM J4B73 mag Ford 4 cyl L Head. Had always had my mags rebuilt by a local shop but the guy who did it retired. He always set my mags to fire on #1. I shipped it off to be done got it back mounted it brought #1 cyl to tdc, tractor wont start all wires where they belong, got plugs out they fire great 1-2-4-3 but not at the right time.I called the mag shop and asked him if he had set the mag to fire on #1 tdc, he says dont need to on a mag you just "move the wires around" till ya get it to go.I ask aren't the rotor and drive shaft timing marked to bring a mag to fire on #1? Next I say why then do they have the cyl #s on the cap------he says I have no idea why they bothered to put cyl #s on the cap. Next ? again to him was why are the shaft and rotor marked to time the mag,he gave me a reason which I could not understand and at that point I wished him a good day. I know how to time the drive and rotor with #1 tdc.Being curious is why I post my ? is he in line with other mag repairmen, and why did the manufacturers of the mag put cyl #s on the cap, I can only come up with one answer.
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Ken Christopherson
01-14-2019 01:04:47




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Re: Magneto ? in reply to WW2N, 01-13-2019 21:32:03
Also, regarding your question about rotor and drive shaft timing - they are set to give spark at a particular point in the rotation of the magneto... It has nothing to do with whether or not the engine is on TDC of #1. They are two separate systems. The magneto is timed internally to give spark at a particular drive lug angle. If the engine crankshaft, camshaft, and governor are in time, and the magneto is bolted up to that system, it (the magneto) is set to fire at the same time in the rotation, every time. Realistically, the governor/magneto drive is what causes the magneto to fire at a specific position in engine rotation. This is all getting WAY more in depth than we need to be.
Essentially, if you bolt the magneto up blindfolded, and hook up your wires, you have a 25% chance of being correct on the first shot. If not, you can simply rotate the wires around to correct the firing order.

On a 2-cylinder JD tractor, it is even easier. Just flip the two wires around and it will go!

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Leroy
01-14-2019 05:29:44




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Re: Magneto ? in reply to Ken Christopherson, 01-14-2019 01:04:47
Yes a JD will go but not correctly as one plug is not firing at the correct time. Found that out close to 50 year ago. I forget the order now as has been too long but they will start easier if wires are at correct place.


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Ken Christopherson
01-14-2019 00:52:39




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Re: Magneto ? in reply to WW2N, 01-13-2019 21:32:03
Magneto's are timed internally, SEPARATE from the engine. Once the magneto timing is set, you do not have to do anything to it - just bolt it on. This is NOT like a distributor. I would guess the gent you sent it to is reputable, and knows what he is doing. I work part time in a magneto/distributor/carburetor shop (doing carburetors).. But know a little about magnetos as that is all I run on my tractors. In order to install a magneto on a tractor, bring whichever cylinder you want to TDC on the compression stroke (preferably #1 cylinder)... Then ensure your rotor is pointing to whatever mag cap terminal you are going to run your wire to #1 cylinder. The numbers on the cap make NO difference (it only matters where your rotor contact is pointing to). Even if you get it wrong, you can rotate the wires either 90 forward, 90 back, or 180. (I have a habit of being 180 out on my timing - usually the more common issue)... Easy to correct, though. If you want to worry about your "#1" marking on your cap being correct with the #1 cylinder - pull the mag off, and cycle it until the rotor is pointing at the correct terminal. If you are 180 out, cycle it twice, and reinstall. The more challenging is when you are 90 degrees forward or back (although still not difficult).
At the shop, we get customers all the time who say their magneto timing is off, then they pull the magneto apart and start messing with the INTERNAL magneto timing gears.... My shop owner has even made house calls to his local customers to show them how to install a magneto because they SWEAR it is the magneto. EVERY time people seem to get so bent on what position the magneto is in. It only matters where the rotor is pointing to, and where you are running your spark plug wires. In a nutshell, whatever cylinder is on TDC of compression, run the spark plug wire from the terminal that is next to fire to that cylinder. Then, follow your firing order in the correct rotation of the magneto.

I hope this helps....

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Den N Ms
01-13-2019 22:19:03




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Re: Magneto ? in reply to WW2N, 01-13-2019 21:32:03
WW2N,Some info for you.Follow instructions below and set your mag to number 1,and engine to just before #1 TDC.





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Den N Ms
01-13-2019 22:29:16




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Re: Magneto ? in reply to Den N Ms, 01-13-2019 22:19:03
WW2N,Some more for you.









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WW2N
01-14-2019 00:32:24




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Re: Magneto ? in reply to Den N Ms, 01-13-2019 22:29:16
Hey Den Im usually on the N forum and have talked to you about your boys Mustang(been a while) and other stuff I have FM Mag book dated 1951 but I will look at your reply you went to a lot of work so I wont let it go to waste. I posted a WW2 2N magneto book on the N site last week it spoke of Patriotic Farmers using steel wheels and crank start. Even the gurus over there dont get involved in mag ?s so I came here. What Im looking for someone who had a rebuild and not set right, ya dont move the wires around like this guy told me. at least not me its my trailer queen. I had this tractor forty years and the mag rebuilt by the same guy 3 times in 40 years. it was a working tractor until 2014

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WW2N
01-14-2019 00:58:08




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Re: Magneto ? in reply to WW2N, 01-14-2019 00:32:24
These are 75 yr old stickers C is clockwise A is for?????? Anti-Clockwise the had not discovered CC Counter Clockwise in 1943.





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Ken Christopherson
01-14-2019 01:15:11




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Re: Magneto ? in reply to WW2N, 01-14-2019 00:58:08
C is for clockwise, A is for counter-clockwise rotation. I am guessing they used A instead of CC so that you wouldn't confuse a single C with a double-C..


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Jeffcat
01-14-2019 08:49:57




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Re: Magneto ? in reply to Ken Christopherson, 01-14-2019 01:15:11
No the A stands for anti-clockwise. Otherwise there would be two C s.

The purpose of timing the rotor to the mag's "armature"/point cam is to have the rotor be lined up with a high-tension terminal when the points open and spark occurs.

If it is timed so it's right for one cylinder, it will be timed right for all.

#1 fires, the rotor moves into position for #2 to fire, and as the mainshaft has turned 1/2 turn the points open and spark occurs. (The rotor has turned 1/4 turn.)

#2 fires, the rotor moves into position for #4 to fire, and as the mainshaft has turned an additional 1/2 turn the points open and spark occurs. (The rotor has now turned 1/2 turn.)

#4 fires, the rotor moves into position for #3 to fire, and as the mainshaft has turned an additional 1/2 turn the points open and spark occurs. (The rotor has turned 3/4 turn.)

#3 fires, the rotor moves into position for #1 to fire, and as the mainshaft has turned 1/2 turn the points open and spark occurs. (The rotor has turned 1 turn and the mainshaft has turned TWO FULL TURNS.)

It is back where it started from and the cycle repeats.

So all you would have had to do was b sure that the rotor was pointing to the @1 terminal and the engine was at TDC.

There could be a quirk, though, because of the 90? drive adapter that only fits in the face of the camshaft one way.

Did you take just the mag to the shop, or the mag and adapter assembly?

Just the mag was sent to be rebuilt Bob. Do you have a FM J4B73 mag if you do I will explain my point what you replied is correct and known. If you dont have the mag its is way to much to type its a picture is worth 1K words thing. I have all cyls hitting as it was intended and match the cap, tractor runs fine other than a bit cold blooded, once it gets a good fire going she is perfect.

"Do you have a FM J4B73 mag"?



Yep.

<img src = "https://i167.photobucket.com/albums/u125/27Grainfield/N%20Ford/FordMagDist1.jpg">
<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/N%20Ford/FordMagDist2.jpg">

See photos: Ok now align the the C on the rotor gear with the beveled tooth or the tooth with a hole in it on the mag drive gear as directed by the sticker on the inside of the main cap. If yours are like mine the rotor will be at the #1 fire position at this point, so I am saying this puts the mag in time with tractor . You turn the motor till you get TDC #1 Cyl. I say it was planned this way by Ford and Fairbanks Morse so you cant say timing on the mag is seperate from the engine timing and I bet if you align the mag and the #1 cyl the lugs on the drive gear will be align with the cam and you can bolt it on and it should start right? keep in mind I left the drive gear on my tractor and just had the mag rebuilt. The mag rebuilder told me no connection of timing of engine and the mag, he said put the mag on the drive gear and no matter where the lugs fit in the drive gear or the pistons are positioned you move the wires clockwise till it starts, yes it will but I want #1 in the #1 hole that is marked #1.Allis Chalmers caps are #ed 1-2-3-4 there is a reason that #1 is marked #1----- do you know why? I now have a running tractor doing it the way I presumed it was correct. If nothing else this is a hand crank start tractor if you move the wires like the rebuild guy says you will also be wore out.Are the lugs on your drive gear like a front mount distributor they only fit one way into the cam shaft if so tdc #1 and it puts the drive gear in time right.

Heres photos

I'm happy that worked for you and that you got the engine running!

However, you are "overthinking" it just a bit.

ASSUMING the mag was in working order/producing a spark when it left the mag guy's place, all you would have needed to do is connect a spark tester to the terminal marked #1 and turn the impulse drive until #1 sparked, then turn the impulse backward a fraction of a turn 'til the tangs lines up with the drive slots, and install the mag.

NO different than installing a mag on any other tractor.

As to why the cap is marked #1, it gives a standard starting point for the mag and wires to be installed at the factory, and if the wires are disturbed, it makes it simple to put them back in place.

The engine will run equally well with the mag installed in 3 more (different) positions, as long as the wires are rearranged accordingly, and that commonly has happened.