Externalizing the coil on J4 mag

Mon Aug 09, 2004 6:39 am

Greetings all --

I've heard a lot about externalizing the coil on the J4 magneto in cases where the internal coil is bad and the issue seems to have cropped up again just recently. Certainly this can be done, but why would one want to? I admit, I'm a bit of a purist and like mags and also I'm relatively new to cubs -- but -- when I got my '47 the mag was a mess. Had to replace the coil, rotor, points, condensor, dist. cap and retime. Was able to find all the parts at either the local Napa or IH dealer. The dealer wasn't all that helpful but Napa had current part numbers for all that stuff and acted like it was no big deal.

Maybe Napa just had a lot of NOS. Are the internal coils really that hard to come by? Maybe I should get an extra just incase.

Just interested to hear the pros & cons, hope noone takes offense.


Pete P.

Mon Aug 09, 2004 6:47 am


The coils are not all that hard to come by, and usually are available at your CaseIH Dealer (usually have to be ordered here with a minimum 2 week wait). The main problems is that the internal coil is VERY expensive (at least here in Canada :!: :roll: :shock: ).

You are correct, the Cub looks much nicer with a proper internal coil in the mag.

Just in case though, I would stock up on an extra coil, especially if they are not all that expensive stateside :idea: BTW, how much IS the coil stateside. I am kind of curious.

As for taking offense, I sincerely doubt if that is gonna happen here. An opinion is an opinion and is regarded as such and awarded the respect that an opinion deserves.

Mon Aug 09, 2004 6:50 am

Pete, most conversions were done as a matter of expediency and cost. It is a quick easy cheap fix using readily available parts. Standard coils as a rule are much cheaper than the mag coil and availbility of the mag coil is sporadic. Most parts houses and dealers for that matter, do not stock them, they must be ordered (if the parts guy is so inclined). So the conversions were done to get the tractor back into the field. I do agree that returning the mag to functionality is the correct permanent fix. But sometimes you just gotta cut grass (or plow, or cultivate or whatever needs to be done) and can't wait for parts.

Mon Aug 09, 2004 7:45 am

Here's a subject that I know something about (thanks to Donny & Bigdog). I am in the middle of rebuilding my J4 magneto. The PO had converted it to an external coil. The internal coil, core and all were missing. The coil will run you between $45 and $50. They are not hard to find but the clips and hold down screws are.

Here are to sources I have used:


Marks's Magneto Service
(860) 887-1094
No web site.

Mon Aug 09, 2004 9:07 am

Many of these replacements were done several years ago by farmers trying to get by on a shoe string. 40 years ago when I did my first one a mag coil cost $30 (about 2 days pay) and would last about 2 to 4 years, but a battery ignition coil cost about $5. It was an easy choice.

Mon Aug 09, 2004 10:05 pm

Thanks all. For some reason I took some of the discussions to indicate that the internal coils were hard to come by. You're right, though, they're ten or more times the cost of an external can-type coil. Rudi -- I paid $ 40 US for a NOS coil at the Napa in Erie, Penna. back in May. This particular Napa is a real good, old school parts house (if I may say so) and they have tons of NOS for trucks, tractors, industrial applications, etc. etc. The gentleman did say that it was their last one and the price could and probably would go higher to order one in.

I've not tried them for the Cub, but for the Bosch, Wico and Eisemann mags of the type used on Caterpillar tractors Standard Magneto of Chicago seems to have most parts or know how to fabricate them. Pricy though.

I'm really learning a lot about these cute little red things here on this site, it's easy to see why the Cub has such a following. Thanks all.

Pete P.