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Farmall Cub • View topic - Mag or not to Mag ...that is the question

Mag or not to Mag ...that is the question

Tue Jul 09, 2013 7:09 am

I have a 1948 Cub and it has a magneto. I have been having issues with it being hard to start lately and I think it is due to the coil in the magneto. This is the third coil I have gone through in 4 years. I have checked the spark and it is orange instead of the blue as mentioned in several posts. I have a distributor that I can put on in place of the mag. I am just not sure that it is the right thing to do.....if it were your cub what would you do? I am teetering back and forth here and don't know what I should do.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 7:15 am

Replace the condenser in the magneto. Try that first.

Your decision. If it is a working tractor, I would either install an external coil on the magneto or fully convert to the distributor.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 10:17 am

Inside most of the wico, fairbanks morse, Edison mags I worked on there is a low speed trip lever that winds up the mag to give it a snap forward which gives it a hotter spark for starting. These levers can get stuck sometimes or something is wrong with the spring windup. It's in the front section under the drive hub. Make sure the points are clean too. Be careful when you install the coil in a mag some had paper wraps to protect the windings.

I find that any engine with a mag seems more dependable when it's working correctly. Or maybe I'm old school but I love hearing the snap of the mag when it idles.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 10:55 am

Eugene and BigBill,
thanks for the quick reply. What I am looking for is if in your opinion there is any real advantage to replace the mag with the distributor...I liked the idea of the mag at first but am souring on it as I have more and more issues that "seem" to be mag related.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 11:33 am

Whatever you decide to do, it is of course your decision! I like mags, and all of mine that originally had one still have one. I don't have any issues with them, and if I were in your shoes, I'd fix and keep the mag, but that's just me. As Eugene mentioned, yours is a working tractor. None of mine are, so that probably has a lot to do with my opinion.

The advantage that the distributor has over a mag is varying timing with advancing throttle settings. It will run better throughout the throttle range with a distributor, especially at idle.
Drawbacks with a distributor are you need a battery to operate it, and a mag has a hotter spark than a distributor the faster it turns.

BigBill wrote:... there is a low speed trip lever that winds up the mag to give it a snap forward which gives it a hotter spark for starting. ..... Or maybe I'm old school but I love hearing the snap of the mag when it idles.

As you mentioned in your first sentence, the impulse is only for starting, and should not "snap" once the tractor is idling.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 12:51 pm

On a very slow idle I could hear the mag snap on mag on the gravely but it could be the valves making noise too they were noted for that with the older L engines.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 1:56 pm

BigBill wrote:On a very slow idle I could hear the mag snap on mag on the gravely but it could be the valves making noise too they were noted for that with the older L engines.


Several years ago I tried reducing the noise output from my generator. So I figured most of the sound was from the exhaust coming through the crummy little muffler. Wrong! After silencing the exhaust note, the generator sounded nearly as loud because of the valves clattering open and shut. The quietest old flathead engine I've ever heard running was 1940 Cadillac V16. That engine was virtually silent - the spinning fan was the only indicator of the engine running.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 2:08 pm

I have run into the problem with mag coils not lasting well, and since I have 3 cubs all with magnetos it is pretty noticeable. The 2 that are kept inside the insulated shed give very little trouble, but the one with the loader that sets under the lean to due to space limitations is frequently hard to start, and seems to need a coil every 2 or 3 years. there used to be a big difference in the quality of Ih coils versus the aftermarket coils. The IH coils were higher but would last longer but were also much higher, which is the reason most of the old working tractors were converted to distributors. I do not know if there is still a difference or not, since I have been buying aftermarket ones.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 5:17 pm

I have 3 working tractors, all on mags. One was rebuilt in 2007, one in 2008, and the last one was probably 2009. None of the three has given any further trouble, nor gone through a coil since then, knock on wood. All three see something around 100 hours of use per year. I don't know if it is coil quality, how it's kept, or how it's used. Now that I bragged on mine, watch them all go out next week while I'm trying to mow!

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 6:39 pm

One advantage to the distributor is that parts are available at your nearest auto parts store. Even on Sunday until 2 PM. I keep an spare points and condenser. Should the coil fail, I can always take one off my other tractors.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 9:21 pm

Charles:

RaymondDurban wrote:Whatever you decide to do, it is of course your decision! I like mags, and all of mine that originally had one still have one. I don't have any issues with them, and if I were in your shoes, I'd fix and keep the mag, but that's just me.


That is pretty much me too, except that none of mine are restored and they all have to work. The mags have not really been an issue for me at all and so far I have only had to replace one coil as my brother-in-law George had put an external one on. My Cubs sit inside now but used to be outside. I had some issues but none with the coil going south. Points were more of an issue and moisture.

If it was my Cub the mag would stay simply because that is how the Cub came. Now, since I just bought a Lo-Boy with a battery ignition, I guess I am going to leave it that way cause that is how it came from the factory :shock: Yeah, I know ... :roll:

And of course .. TIJIMHO.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 9:43 pm

Eugene wrote:One advantage to the distributor is that parts are available at your nearest auto parts store. Even on Sunday until 2 PM. I keep an spare points and condenser. Should the coil fail, I can always take one off my other tractors.
Points, condenser and dist. cap are the same for the distributors, and J4 mags. Different condenser for H4 mags though. Neighbor had points go bad in his IH 440. he was going to make a trip to town to get some. I just went to the shed and grabbed my spares for the cub and told him to get me a set of replacements. i do not know how long IH used the same points and condensers, but it was a long time.

Re: Mag or not to Mag ...that is the question

Tue Jul 09, 2013 9:50 pm

Most of the Mag related issues come from folks that do not know how to work on them. That being said I have only one cub with a mag on it and it is for sale :D But I am not a mag guy. all the rest are 12 volt with Distributors. Parts cost is a huge factor with a mag Rotor and coil, and the lack of knowledgeable people to work on them. Rick will fix you up I am sure. But the parts are much higher. If you have to get someone else to repair the mag going with a distributor may be your best way.
Boss

Re: Mag or not to Mag ...that is the question

Wed Jul 10, 2013 10:41 am

You already know my reply !----battery ignition is the only way to go ---and 12-volts!!!!!lol!! Thanks;sonny