J4 Magneto hook-up question.

[BeeGeezer]

I recently rebuilt the magneto and I can't remember which wire goes to the terminal screw on the mag.
The tractor doesn't have a proper wiring harness, only three wires. One of them comes off of the starter terminal which is hot at all times. The posts on the amp meter are hot, but not the ones on the push/pull switch. The other two are not hot. I believe these two are for the generator. Currently, I have two wires that are not connected, on hot one not. My question is, does the hot wire go to the terminal on the magneto? I am a little nervous about connecting this wire as I don't know much about mags. I would hate to mess this up due to lack of knowledge.

Thanks

[Mht]

No. Don’t connect a hot wire to the magneto. The terminal on the magneto connects to ground thru a switch to turn the tractor off.

[BeeGeezer]

Thank you. I think I will get a wiring harness and go from there.

[k hutchins]

You didn't say if you were working with a 4 position switch or not. I will assume you are. I made new harnesses for both my '48s using the above diagram. I used #10 wire the main wires and #12 for the lights and shut off switch.

Hope this helps, simplest easy to follow diagram l found.

[Gary Dotson]

The wire to the magneto is simply a kill wire, the push/pull switch simply grounds the mag terminal to shut the tractor off, it will run just dandy with nothing connected to the terminal, on the side of the mag. the mag. kill wire is separate from the main wiring harness. You'll notice it's not included in the diagram posted above. The magneto is totally separate from the tractors main electrical system. A new harness purchase may or may not include that wire, you might have to ask for it.

[BeeGeezer]

cubwire.jpg

You didn't say if you were working with a 4 position switch or not. I will assume you are. I made new harnesses for both my '48s using the above diagram. I used #10 wire the main wires and #12 for the lights and shut off switch.

Hope this helps, simplest easy to follow diagram l found.

Yes, that does help. I think I may use that when I get some lights.

[BeeGeezer]

The wire to the magneto is simply a kill wire, the push/pull switch simply grounds the mag terminal to shut the tractor off, it will run just dandy with nothing connected to the terminal, on the side of the mag. the mag. kill wire is separate from the main wiring harness. You'll notice it's not included in the diagram posted above. The magneto is totally separate from the tractors main electrical system. A new harness purchase may or may not include that wire, you might have to ask for it.

I think I am beginning to get the picture. My test light does not light when I test the poles on the switch, no matter which position the switch is in. Shouldn't it, or is that dead wire the ground wire you're speaking of? The switch only has two positions, on/off, and is so old there is no writing on it and the plastic is near about worn completely off. I can't remember if it is in to run or out. I thought a test light would tell me, but I get nothing from either pole with the switch in either position. Burned out switch?
I noted the position of everything as I was taking everything apart, so I am fairly sure I got it all put back together right.
I know the tractor ran, I have used it. It has just been sitting in the barn for years while I have been away working.

Thanks again for your time.

[Stanton]

There should be a single wire (#12ga or #14ga) that runs from the single prong at the rear of the ignition switch to the side of the magneto. That’s it; totally separate from the wiring going to the light switch knob.
Pull out to run, push in to kill.

[BeeGeezer]

There should be a single wire (#12ga or #14ga) that runs from the single prong at the rear of the ignition switch to the side of the magneto. That’s it; totally separate from the wiring going to the light switch knob.
Pull out to run, push in to kill.

Understood, Thank you. I do have a new switch, I think I'll go ahead and change it.

[Rick Spivey]

I think I am beginning to get the picture. My test light does not light when I test the poles on the switch, no matter which position the switch is in. Shouldn't it, or is that dead wire the ground wire you're speaking of?

There will be no "power" on the magneto kill wire, it simply grounds the points out to kill the spark. You can test the switch using a continuity test to any good ground location. That will determine that your switch is good or not.

[Gary Dotson]

From your description, it sounds like your 1 prong switch has been replaced with a 2 prong. In this case, one wire will go to chassis ground and the lead to the magneto connects to the other, it doesn't matter which way they are connected. With that set-up, out will be off and in will be engine run position. It works ok that way, just confuses people familiar with the normal, out to run, set-up.

[BeeGeezer]

From your description, it sounds like your 1 prong switch has been replaced with a 2 prong. In this case, one wire will go to chassis ground and the lead to the magneto connects to the other, it doesn't matter which way they are connected. With that set-up, out will be off and in will be engine run position. It works ok that way, just confuses people familiar with the normal, out to run, set-up.

Yes, that is correct, I have a two prong switch. You are also correct when you said it confuses people of which I am one.
Thanks again.

[BeeGeezer]

My Cub is now running, so I did a little hilling in the garden. The throttle was not responding correctly, but does seem to be improving on it's own. That may become the subject of another thread, though.

Thanks everyone for your help.

[Glen]

Hi,
TM Tractor has new ignition switches for Cubs with a magneto, if you want one.
One is Case IH, it says. One costs less than the other.

http://www.tmtractor.com/new/el/605fp.htm

http://www.tmtractor.com/new/el/1176fp.htm

You didn't say the year of your Cub.

Below is a page from Walmart, the 1st switch on the page is like they originally came with, if it serial number 224400 or below, the Cub parts manual shows.

https://www.walmart.com/search/?query=54207db

[Stanton]

My Cub is now running, so I did a little hilling in the garden. The throttle was not responding correctly, but does seem to be improving on it's own. That may become the subject of another thread, though.

Thanks everyone for your help.

Glad you got it running again. Remember, if you need to take your carb apart for cleaning, after removing the screws, lift the top straight up so you don't break off the idle tube that's connected to it.