'51 Cub - positive ground

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BartVD
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'51 Cub - positive ground

Postby BartVD » Mon Oct 30, 2023 12:26 pm

Hi,
Working on the Cub, and reading about the electrical system I see that it should be a positive ground.
But the negative cabel is fitted to the chassis.
Can it be converted?
Tried to crank it with negative ground and engine goes around.

What can go wrong when some one made it negative ground?
What will work and what not?

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ricky racer
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Re: '51 Cub - positive ground

Postby ricky racer » Mon Oct 30, 2023 2:42 pm

6 volt or 12 volt conversion?
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Re: '51 Cub - positive ground

Postby Eugene » Mon Oct 30, 2023 3:15 pm

As Ricky Racer indicated you need to fully identify what you have. That includes the type of ignition system and electrical system.

In general.

6 or 12 volt starter and ignition will work, on both a positive or negative ground. 12 volt ignition will need a ballast resistor or resistor inside the coil. 6 volt system, no resistor.

The regulator needs to be polarized to work on both types of grounds. You may have to swap the amp meter wiring to match the ground.

12 volt alternator, negative ground.
I have an excuse. CRS.

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Re: '51 Cub - positive ground

Postby BartVD » Tue Oct 31, 2023 3:25 am

Image

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Re: '51 Cub - positive ground

Postby BartVD » Tue Oct 31, 2023 3:31 am

Ignition Coil is not original. Previous owner placed a VW Beetle coil.
I ordered an original.

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Re: '51 Cub - positive ground

Postby Eugene » Tue Oct 31, 2023 9:46 am

Prime the oil pump.
I have an excuse. CRS.

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Re: '51 Cub - positive ground

Postby Jim Becker » Tue Oct 31, 2023 10:33 am

From your pictures, it appears that you have an original type system. The replacement coil should work properly with the rest of the system. Those components will all function grounded either way. It WAS originally positive ground. After installing the battery (either way), you need to polarize the generator to match the ground. Do that by briefly jumping from the BAT to GEN terminals on the regulator.

Current parts with red repaint on a yellow tractor indicate somebody got it running with used parts. Replaced regulator suggests they got the charging system working at that time. Before doing much with it, you may want to test the generator to see if it works or needs repair. It looks like you need to replace most of the wiring.

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Re: '51 Cub - positive ground

Postby Peter Person » Tue Oct 31, 2023 11:15 am

Are the plug wires Copper Core?
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Re: '51 Cub - positive ground

Postby Jim Becker » Tue Oct 31, 2023 11:45 am

Peter Person wrote:Are the plug wires Copper Core?

No those are resistance cables, need to be replaced with solid core.

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Re: '51 Cub - positive ground

Postby Glen » Tue Oct 31, 2023 6:25 pm

Hi,
The Cub looks in good condition in your pictures.
Below is info about priming the engine oil pump, in a post I wrote on. My post is part way down the page.
The engine can be damaged if there is no oil pressure when running.
viewtopic.php?f=1&t=91765&start=60

In the 1st pic, I see a part for the PTO lever is gone. If you are going to use the PTO, it won't work right without the PTO Guide, it is called. It bolts on the transmission cover bolt on the corner of the cover.
It has been gone for some time, seeing how much dirt is there.

http://www.tmtractor.com/new/pt/245fp.htm

Maybe you have another Cub, and can see how it works on that one.
With the lever so far ahead, the parts inside the housing may have come out of engaged. The lever pin has to go in the PTO clutch groove. Remove the transmission oil fill plug, which is in your 1st pic above, just to the rear of the gear shifter, and shine a light in the hole, and you can see when the pin is in the groove, then put the Guide in place, and put the bolt in. The PTO lever should spring up, to lock it in place on the Guide. You have to push the lever down to move it from disengaged to engaged, or engaged to disengaged. Lube the lever if needed, so it works up and down.
The operator's manual tells how to work the PTO. :)
Last edited by Glen on Wed Nov 01, 2023 11:07 pm, edited 1 time in total.

BartVD
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Re: '51 Cub - positive ground

Postby BartVD » Wed Nov 01, 2023 7:58 am

There is indeed something wrong with the PTO lever. It's disconnected inside, I suppose.
Will remove transmission cover to check after I have engine turning.
I did prime the engine oil pump so hope this is ok.
Have orderd repair set for the carburator and gone let it ultrasoon cleaned.
Radiator is leaking so is gone for repair.

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Re: '51 Cub - positive ground

Postby Don McCombs » Wed Nov 01, 2023 8:24 am

You won’t be able to see any of the PTO mechanism with the shifter cover removed. Look through the transmission fluid fill hole.
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Re: '51 Cub - positive ground

Postby Eugene » Wed Nov 01, 2023 10:12 am

Conduct compression tests. You probably have a stuck valve or two. Cub engines have a tendency to stick valves from sitting for a length of time.
I have an excuse. CRS.

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Re: '51 Cub - positive ground

Postby Glen » Thu Nov 02, 2023 1:10 am

Hi,
Only the transmission shafts, gears, shifter yokes, and other trans parts are in the trans, under the shifter cover.
The trans is in the front area of the housing, the differential is in the rear area of the housing.
There is a wall between the trans and the differential areas of the housing.
The PTO is in the differential area of the housing.
The PTO can only be seen through the trans oil filler plug hole. The Cub service manual says to look in through the hole to put the PTO together.
The PTO comes out the rear of the trans housing.
Below are pics.
The 1st pic shows under the trans shifter cover.
The 2nd pic shows in the rear of the housing, with the PTO and rear cover removed, you can see the wall inside the housing.
The 3rd pic, from TM Tractor Parts, shows the pin, at the bottom of the lever, that runs in the PTO clutch groove, in the 4th pic. That is the front area of the PTO shaft in the 4th pic.
The lever makes the PTO clutch slide back or ahead, to disengage or engage the PTO.
The pin should be round also, so it mostly fills the PTO clutch slot. Sometimes they wear and are flat on part of the pin, then the PTO can slip out of engaged.
I'm not sure if the 4th pic is from TM Tractor Parts or not.
The lever and shaft isn't there in the 2nd pic, it looks like. It goes in the side of the housing, by the shaft in the upper part of the pic.

You probably don't have to disassemble anything, if you remove the trans oil filler plug, and work the lever pin into the PTO clutch groove, then install a PTO Guide to hold the lever in position, if all the parts are there inside the housing. Sorry for the sort of long post.
Attachments
Cub trans 4.JPG
Cub trans 24.jpg
Cub trans 24.jpg (51.92 KiB) Viewed 203 times
Cub PTO lever and shaft.jpg
Cub PTO 4.jpg

BartVD
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Re: '51 Cub - positive ground

Postby BartVD » Thu Nov 02, 2023 7:26 am

Thanks a lot for all the advice.
Think will look quite a few times through this topic.
What an amazing knowledge prestented here.


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