convert to 12 volt and loosing power

[pett3227b]

Hello, I have some questions for the forum. I am a happy owner of a 47 or 48 farmall cub. I want to convert and upgrade to a 12 volt system. I understand that I have a magneto instead of a coil. As a side note I also have a problem of loosing power after running for 45 minutes or so. It starts just fine again after it cools off. I was told that to fix it I should check the coil and valve clearances. I am wondering is there something like a coil in the magneto that could present the same problem? I have been using a 12 volt battery for 2 decades to run my cub. I definitely have the original starter generator. Is there any way that maybe my cub was converted to 12 volt before I got it and still have the starter generator and not a modern alternator? I need to know the steps necessary to convert to 12 volt and material list of parts. Thank-you and I don't know how the farmers got by long before the internet and forums to get information about a specific problem.

[Eugene]

Your loss of power around 45 minutes of engine operation is a typical coil fault. There is a coil inside the magneto. Search function, top right of this page for articles on replacing the magneto coil.

Alternator conversion. Use the search function. There are numerous articles on the task and materials required.

Your tractor's electrical system could have been converted to a 12 volt generator.

[Glen]

Hi,
There is originally a coil in the magneto, it is under the cover on top of the magneto.
The ignition wire coming out of the cover on top of the magneto gets power from the coil.

Below is a listing from TM Tractor for a new magneto coil. You can look at the pics.
There is a rectangular bar that goes through the center of the coil, keep it and put it in the new coil.
It can fit tight.

http://www.tmtractor.com/new/el/713fp.htm

The cover over the ignition points and condenser has to be removed to disconnect the small wire made on the coil. That is a good time to replace the points and condenser.
The points have to be good for the engine to run good. They get old and burned from use.

TM Tractor has those. They have the magneto cap, rotor, and other magneto parts also.

http://www.tmtractor.com/new/el/367fp.htm

Below are pages from the 1949 Cub operator's manual, showing the points and condenser, and setting the point gap.

http://farmallcub.com/rudi_cub/www.clea ... age-30.jpg

http://farmallcub.com/rudi_cub/www.clea ... age-31.jpg

It is a good idea to turn the engine to number 1 cylinder TDC before removing the plate over the points.
Note where the rotor is pointing before removing the plate over the points.
The manual says don't turn the engine when the plate over the points is removed, you can lose the timing. But sometimes it has to be turned a small amount, using the fan, so the right side point is on the high part of the cam. Keep track of which way you turn it.

The rotor is gear driven.
It might need the gear area cleaned and greased while you have the cover off.
Below is a pic of under the gear cover.
Check the timing marks on the gears, they should be aligned.

[Glen]

Hi,
If the Cub works ok on 6 volts, it doesn't have to be 12 volts, it's your choice.
But if it has a 6 volt generator, it should have a 6 volt battery.

Below is a page from the 1947 Cub operator's manual showing the electrical system with the hood off.

http://farmallcub.com/rudi_cub/www.clea ... age-33.jpg

There is originally a plate on the gen with the model number, at the left of the plate.
The model number of the 6 volt Delco gen used with the Relay system was 1101355.
The electrical system was positive ground also.
You probably need to remove the hood to see the plate.

IH changed Cubs to 12 volts in mid 1964. They had gens about the same size as the 6 volt gens. They used gens until mid 1975, when they changed to a Delco alternator.
The 12 volt gens are different than the earlier 6 volt gens, the 12 volt gen is vented, or open, it has a fan at the front.

[Don McCombs]

Brillman also has the J4 magneto coil.

[Mht]

I can highly recommend Brillman for all of your ignition and electrical needs. Especially parts to make great battery cables

[pett3227b]

I am now wondering how to check my generator to find out if it is generating power.IS there also a way to check at the battery to see if I am recharging cause wiring could also be a problem. I may not convert to 12 volts if all I need to replace is the coil in the magneto. Still not sure if my system is 12 or 6 volt I will take a look at the generator to see if its original or not. Is there a way to test it? I am told that some people have a original generator converted internally to 12 volt. Thank-you

[Don McCombs]

Check out the troubleshooting charts about 1/3 of the way down the first page of this thread.

viewtopic.php?t=109148

[Eugene]

I am now wondering how to check my generator to find out if it is generating power.IS there also a way to check at the battery to see if I am recharging cause wiring could also be a problem. I may not convert to 12 volts if all I need to replace is the coil in the magneto. Still not sure if my system is 12 or 6 volt I will take a look at the generator to see if its original or not. Is there a way to test it? I am told that some people have a original generator converted internally to 12 volt. Thank-you

First thing you need to do is identify the generator. Black tag = 6 volts. Red tag = 12 volts.

The generator could have been converted to 12 volts, but probably not.

Are you charging up the 12 volt battery every so often? If so, the generator is probably 6 volts and not working.

You can motorize the generator to see if it will charge. How to do that - search function.

Thought to research - using an external coil on the magneto to operate the ignition system. Again search function.

Also research converting to a single wire 12 volt alternator. It's usually less expensive than repairing the 6/12 volt generator and replacing the voltage regulator.

[Glen]

Hi,
The ammeter on the dash shows if the generator is charging. If it charges, or discharges, the ammeter should show, unless it doesn't work.

Hard to say if the charging system works, you said you have used it for 20 years with a 12 volt battery. It would have been good to remove the generator belt when you started using the 12 volt batteries, since it won't charge a 12 volt battery.
I don't know what happens when it is connected to 12 volts, I guess it didn't have overheating or fire.

If you are going to use a 6 volt battery, I don't know if your Cub still has the original 4 position charge and light switch. You have to choose the charge rate yourself, the Relay system was used before voltage regulators on Cubs.
Below are pages from the 1949 Cub operator's manual, telling how to use the 4 position charge and light switch, beginning at the lower left of the 1st page.

http://farmallcub.com/rudi_cub/www.clea ... age-34.jpg

http://farmallcub.com/rudi_cub/www.clea ... age-35.jpg