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Mag problem update

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10-11-2002 08:20:55

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I reinstalled the mag in the tractor after resetting the points to .20 and realigning the bevel gear with "C" on the fibre gear and got no spark. What else could be wrong-points and condensor are new.

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10-11-2002 13:45:32

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 Re: Mag problem update in reply to Jim-IL, 10-11-2002 08:20:55  
Jim, Take the magneto back off the tractor and clamp it in a vise by the bottom lug. Remove both caps. On the back end of the coil you will see a copper strip that contacts the brass rod coming from the outer cap. With a long handled screwdriver grounded to the case check the spark to the contact.By tripping the impulse you should get 1/2" or more of blue spark. If you have spark you either didn't have the rotor timed right or the spark is going to ground through one of the caps. If you have no spark make sure the points are clean and none of the wires attached to the points are grounding somewhere and try it again. If still no spark, dissconnect the kill wire from the points,sometimes the bushings and washers are bad or installed wrong where the kill wire stud goes through the case. If you still have no spark at this time you might be better off ending it out to a mag shop. You could have weak magnets, but not likely. The magnets holders could have slipped on the shaft (common) or the coil could be bad, or your new. If you find the problem time it up per Dueys post and it will work.

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10-11-2002 13:48:17

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 Re: Re: Mag problem update in reply to Butch(OH), 10-11-2002 13:45:32  
At the end of my post I ment to say, "or your new parts could be bad". I just did a FMJ with a repair kit from TSC and the rotor was no good.

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Duey (IA)

10-11-2002 12:58:08

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 Re: Mag problem update in reply to Jim-IL, 10-11-2002 08:20:55  
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

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10-13-2002 20:13:30

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 Re: Re: Mag problem update in reply to Duey (IA), 10-11-2002 12:58:08  
My B started on two pulls of the crank this summer, but now it won't start. I figure that the cold weather has stiffened the impulse so it won't work. Don't hear the impulse clicking at all. If it will start by pulling, or rolling down a hill, I think that would prove the problem. I suppose bringing the magneto inside and warming it up good might help. Otherwise, some degreasing will be necessary. I would guess that is the main reason most farmers were so quick to change over to distributers in the cold country.

I put a little paint mark on my crank pulley so I could see when I was just about at the firing mark. (You still need the thumb in the sparkplug hole to tell whether you are on firing position, or 360 degr off.)

Once you know your timing is correct, then the next time, before you take the magneto off, note where the rotor points. Then don't touch the engine crank till you put it back together again the same way.

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10-14-2002 12:18:19

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 Re: Re: Re: Mag problem update in reply to cdmn, 10-13-2002 20:13:30  
I just found this site & its great. My brothers 49-C has similar problem in that it will start up but as soon as you put a load on it it quits & will not re-start untill you re-time the engine. Any help would be greatly appreciated.

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Duey (IA)

10-14-2002 14:42:19

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 Re: Re: Re: Re: Mag problem update in reply to ll356, 10-14-2002 12:18:19  
Once set, the timing should NOT change. Sounds like a key sheared. Time to take it apart and fix it. Duey

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10-15-2002 06:06:29

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 Re: Re: Re: Re: Re: Mag problem update in reply to Duey (IA), 10-14-2002 14:42:19  
Im sorry, its not the timing that is changing its the point gap that I have to keep re-setting once its under load.

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10-16-2002 19:45:07

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 Re: Re: Re: Re: Re: Re: Mag problem update in reply to ll356, 10-15-2002 06:06:29  
If your point gap keeps changing the point cam is too rough and is wearing your point rubbing block,or lack of lube, or the bushing is loose in the front plate. I have found some the pin is bad the points pivot on. I hope this helps. Earl In Illinois

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10-11-2002 11:15:59

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 Re: Mag problem update in reply to Jim-IL, 10-11-2002 08:20:55  
Did you check the coil & magnets? Coil could be shot or magnets weak. I think that somewhere in the archives there is a write-up on how to rejuvinate the magnets. (My $0.02 worth. jal-SD)

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