Farm Equipment - Model B 12v spark trouble

Print Page | Close Window

Model B 12v spark trouble

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=10193
Printed Date: 22 Jan 2025 at 9:58am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Model B 12v spark trouble

Posted By: trhod12
Subject: Model B 12v spark trouble
Date Posted: 28 Mar 2010 at 11:50am

I had my B parked outside, and we had one of those great Ohio spring snows. It was running fine, until after the snow. When I started it up, black water spray shot out of the stack and the hood is now speckled black from it. This has happend before, and i always cover the stack w/ a 5 gal bucket. After the snow, It started, but was running rough. I brought it into the garage to thaw out, then parked it outside again. The next day, it wouldn't start, so I put it into the garage again for a couple of hours, and it started, but is sputtering pretty good.

The plugs are wet (gas), and I have a yellow/orange spark. I've been talking to a local model B guy who told me to ask on the forum, cuz he is not familiar with the coil conversion. It appears my tractor has been converted to a 12v system and the magneto was replaced with a coil(see pictures). The plug cables are the "radio suppressant", which he said I can't be used on this tractor, due to the magneto. Are these cables ok with the coil setup?? It seems like my problem is spark related, and not fuel related.

Here are some pictures to try and help illustrate my system.

Picture of distributor from distance:

Closer view of distributor (I believe the black cylinder on top is a coil)

Opened up distributor showing rotor. Take note of black wire near top. This wire is soldered to the distributor cap, runs thru the back of the distributor (near the engine block) and then plugs into the black cylinder on top of distributor (I believe to be a coil)

Close up pix of inside of distributor, showing rotor. What is the silver cylinder in front??

Close up of distributor cap. Note black wire that is soldered to the pin on distributor cap. Points appear black in color, no corrosion apparent.

I am somewhat mechanically inclinded, but know just enough to get my self into trouble, and often times, not enough to get out of trouble. So any help you have would be great. any and all info would be helpful. Don't feel like you would offend me if you keep your explanation very simplistic. This is pretty new to me. Just to reafirm, the tractor was running fine until it sat out in the snow the other night.

Replies:

Posted By: norm [ind]
Date Posted: 28 Mar 2010 at 12:04pm

that is i call a barnyard conversion wrong mag for an a-c all is open for moisture have seen many of these a c heap way to make a tractor run you also need correct plug wires my 2 cents

Posted By: trhod12
Date Posted: 28 Mar 2010 at 12:21pm

Jeff,

I can't find your post response, but you said to check the point gap....would the point gap of 0.020 in the manual still apply with the conversions that have been made to the tractor??

Posted By: trhod12
Date Posted: 28 Mar 2010 at 5:05pm

Well, it was a rainy day so I decided to tear into it.

New plugs, wire(got the non radio suppression type), and fuel filter. Sanded the contacts on distributor cap. They were a little pitted and uneven. Cleaned everything out, put it back together, and she is purring like a kitten.

I still wonder if this setup is a common one, as the B that I have seen didn't have the black cylinder on top, that I assume is a coil.

Thanks for any input you might have.

Posted By: steve(ill)
Date Posted: 28 Mar 2010 at 5:17pm

the setup is not "common" , but it was a cheap way to get the tractor to run. THe original coil is inside the mag and coated with tar. AFter 15-20 years it breaks down and dont work. That would be 1970 era ? By then there were a lot of guys that understood how an automotive coil worked, and you could buy one for $8. The mag coil is about $50. They were not going to originality, jus trying to get by on the cheap. Mounting a car coil on the outside and drilling a hole in the side of the old mag was a way to get by. There are probalby hundreds of them around, most have now been converted back to mag or upgraded to distributors.. It works, but as you found out, got to keep it dry.

-------------
Like them all, but love the "B"s.

Posted By: trhod12
Date Posted: 28 Mar 2010 at 6:00pm

AHH. that would make sense. So the problem arises because of the hole drilled in the magneto housing, for the coil wire to pass thru??? Is that why this setup causes moisture on the points??

Posted By: CTuckerNWIL
Date Posted: 28 Mar 2010 at 8:12pm

Moisture in the mag is only one of your problems. If you are going to have to leave the B out in the weather, a can or bucket over the muffler evidently isn't enough. If the muffler fits inside the manifold then water can run down the outside of the muffler and enter the manifold. Over time this can do considerable damage to valves ,seats, cylinders and rings. You could even get enough water in there to freeze ad break something. Some people have tapped the inside of the manifold ad sealed a pipe nipple into it. Then the muffler can clamp on the outside so water can't get in.

-------------
http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF

Posted By: Steve in NJ
Date Posted: 28 Mar 2010 at 9:05pm

Well, it looks to be a "K" series Mag, which isn't really the incorrect Mag, its just one that was more pre-domonate on say a WC model Tractor. The Black cylinder is a coil, and as Steve mentioned is a cheap way to temporarily fix an expensive internal coil problem. The Mag that was most common on a B model was the "J" series or FMJ4B3 as its known. Good move on the wire change. Suppression wires are NOT for Mag fired Ignition systems. One thing you do need to do with that setup is keep it out of the snow and rain. If you want to remove the external coil off the Mag and install the correct coil, I have them in stock. In the "K" series Mags the tar-taped coil was the norm, and they failed as Stevo mentioned. Good luck and keep er' dry.......
Steve@B&B

Posted By: trhod12
Date Posted: 28 Mar 2010 at 10:52pm

Steve in NJ wrote:

Well, it looks to be a "K" series Mag, which isn't really the incorrect Mag, its just one that was more pre-domonate on say a WC model Tractor. The Black cylinder is a coil, and as Steve mentioned is a cheap way to temporarily fix an expensive internal coil problem. The Mag that was most common on a B model was the "J" series or FMJ4B3 as its known. Good move on the wire change. Suppression wires are NOT for Mag fired Ignition systems. One thing you do need to do with that setup is keep it out of the snow and rain. If you want to remove the external coil off the Mag and install the correct coil, I have them in stock. In the "K" series Mags the tar-taped coil was the norm, and they failed as Stevo mentioned. Good luck and keep er' dry.......
Steve@B&B

Thanks Steve, I will keep that in mind if this continues to be a problem.

I do usually keep the tractor in a shed at the farm, but I had brought it home to do some springtime TLC and got caught in an Ohio springtime flurry. I'm gonna get a tarp over the frontend tonight to help eliminate this problem.

To all, thanks for all your input. It has been very helpful.