1947 Cub 6V to 12V conversion

[AHS]

I use my Cub in the fall/winter, sometimes not for a month. To start it is a headache. Ok, the starter, the magneto.. ok to use with 12V? Which kit to buy? I want a good one! I have no clue about this! Thank you!

[Eugene]

12v conversion will be ok. The magneto is separate, not involved with the battery/alternator. The 6 volt starter will work on 12 volts.

Suggest using a 12 volt single wire alternator. Dirt simple to wire up.

Search this site for information on installing a 12 volt alternator conversion. This site has several different how to procedures. Some are DIY manufactured mounting brackets and some kits.

[Glen]

Hi,
People on here have said that if the Cub engine needs a tune up, making it 12 volts doesn't really solve much.
They have said that a well tuned up engine starts well in cold temperatures using the original 6 volt system.
Below are things to check or replace for a tune up.
The magneto has ignition points, condenser, rotor, and cap. The points get old and burned from use, just that can cause hard starting, and make the engine not run well.
The rotor and cap contacts can get burned from use.
The condenser can go bad, it may not run any if that happens.
The coil in the top of the magneto can get weak, and make a weak spark, a common thing on Cubs, that can cause hard starting.
The magneto timing could be wrong some, that can make it start hard, and make the engine have less power than it should when it is running. It's important that the timing be set right.
The spark plugs can get fouled, that can cause hard starting.
The spark plug wires get old, they sometimes don't work well if they are too old.
You didn't say if the engine has had a complete tune up lately.

There is a test you can do to see the power of the spark the magneto coil is making, say if you want to test it, and we can write info how to.
It tells how to time the magneto to the engine in the 1947 Cub owner's manual.
If the bushings in the starter are worn from use, the armature in it can rub inside the starter, that can make the starter run slower than it should.

[AHS]

Glen, 2 maybe 3 years ago i did plugs, condenser, points, coil, wires, carb. She runs good, but its just starting it. “The starter is good” the past owner said. He took it off and brought it into a starter shop and they said said was good. Im interested in the magneto check.

Ok, so the points + condenser
Coil and magneto all able to be used with 12v?

[staninlowerAL]

Don't forget to check/adjust the valves as a part of the "tune-up", also a compression test will tell you a lot about the "health" of your engine. All of the advice listed above will help get you on the right track. The assumption is this tractor is standard factory equipped with a J-4 magneto without any changes or modifications. If you truly want to change to 12v for starting purposes then you are probably going to need to change to a 12v charging system also. That involves replacing the 6v gen with a 12v alternator for the electrics other than the engine ignition system (which as has been point out is totally dependent on the output from the mag coil to run the engine, which will still be 6v since the mag is totally independent of the battery and charging system). Also a 12v battery and any other electrical such as lighting. A good resource is found in the manuals section and is GSS 1012 ELECTRICAL EQUIPMENT. This manual is a complete explanation of both the battery and magneto electrical system and gives instructions on how to service and repair them. JMHO Stan

[Glen]

To do a spark test, remove the center spark plug wire from the magneto cap, hold it by the insulation with the metal end about 1/4" from a bare place on the engine.
Put the transmission in neutral, turn the ignition switch to on, and run the starter. The spark should be blue or white, and jump the gap. A yellow spark is weak, and needs improving, the engine may not run, or start harder than it should.
I would charge the battery fully before doing the spark test.
Be sure the Cub doesn't roll during the test.

Ok, so the points + condenser
Coil and magneto all able to be used with 12v?

Yes, if the magneto is using the original style coil, under the cover on top of it.
The magneto isn't connected to battery power, it makes it's own power.

I would remove the spark plugs, and see if they look good. Sometimes they are wet, or black, with gas or oil. That can make it start harder than it should.
If they are wet, dry them, and sand the contacts with fine sandpaper, so they are shiny metal. Wipe off all sanding with a clean rag, between the contacts also.
Check the gaps, they should be .023", the owner's manual says.
Clean around the bases of the spark plugs before removing them, so any dirt doesn't fall into the engine.

[ricky racer]

To start it is a headache.

What do you mean "to start is a headache?"
1.) Does the starter not spin the engine over fast enough?

2.) Does the starter spin over the engine okay, but it just won't fire?

If the problem is #1 I'd suggest you check the battery with a load test to verify the battery is up to snuff. If the battery is good, and battery connections are clean and tight, replace the battery cable from the battery to the starter. Id suggest using a #2 welding cable which can be purchased at any welding supply house, TSC or Rural King and some hardware stores. Don't just go to the auto parts store and buy a battery cable they might have there, it won't be heavy enough for a 6v. system. Also, verify that the positive ground has a good connection to the frame. If you use the tractor infrequently, invest in a battery maintainer to keep your battery fully charged and in good shape. This is a whole lot easier and cheaper than converting to 12v.

If the problem is #2 I'd suggest you do a dry/wet compression test to verify the condition of the engine.
If compression improves with the wet test the cylinders and or rings are worn and need addressed. If the compression is too low a 12v. conversion won't do a thing and will be just a waste of money.

If the compression doesn't improve with the wet test, check and adjust the valves and test again.

[Eugene]

Is the 6 volt charging system still working? If not it's practical to convert to 12 volts.

[Glen]

Below is a listing at TM Tractor Parts for a 6 volt battery to starter cable, like Ricky talked about above. It says it is number 2 cable. You can look at the pictures.
http://www.tmtractor.com/new/el/2581fp.htm

[Jim Becker]

I will underscore the value of a battery maintainer. This is particularly important if it sits for a month at a time, whether you convert to 12 volts or leave it at 6. If you regularly connect a maintainer, you won't even need a charging system.

[ricky racer]

I will underscore the value of a battery maintainer. This is particularly important if it sits for a month at a time, whether you convert to 12 volts or leave it at 6. If you regularly connect a maintainer, you won't even need a charging system.

Good point!

[inairam]

6 volts batteries typically have substantially more cca than 12-volt batteries. My " fleet" is a mix of 6 and 12 volts including a 6v 130 with an engine 2 x the size of the c-60 in the cub. My 6 volters are better starters across the board than my 12 volters. The 130 uses the same size battery as the cub.

In the summer on flat ground, I have started my 6 voters with the pto mower engaged while in 2nd gear to prove a point.

A few things I would check:
1) cables and connections. AWG2 for both to the starter and the ground.
2) I started using all NAPA parts on the ignition. I had a lot of issues with points and condensers from the tractor websites
3) Multi weight oil
4) a good tune-up including valve adjustment as others have mentioned

[AHS]

Ok, i will replace my cable from my battery to the starter. It charges just fine, at hi or lo. Ok, a battery maintainer all the time. (I only throw it on there when i need to get it started). 2 or 3 years; New battery too. It just does not spin over fast enough, and the cable from the the battery to the starter gets warm, (not hot)just warm. I think that a sign that the cable needs replacing.

[ricky racer]

Ok, i will replace my cable from my battery to the starter. It charges just fine, at hi or lo. Ok, a battery maintainer all the time. (I only throw it on there when i need to get it started). 2 or 3 years; New battery too. It just does not spin over fast enough, and the cable from the the battery to the starter gets warm, (not hot)just warm. I think that a sign that the cable needs replacing.

I agree. Report back and let us know your results.

[Eugene]

Ok, i will replace my cable from my battery to the starter. It just does not spin over fast enough, and the cable from the the battery to the starter gets warm, (not hot)just warm. I think that a sign that the cable needs replacing.

Move the battery ground cable from the battery box to the transmission. Reason, battery box sheet metal corrosion.