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O-12 project

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So this is my project for the winter. Got her moved into the shop the other night. She needs alot of love. The motor is seized and there is alot of rust. But who doesnt love a good challenge. I'm going to start tearing her down later this week to see how bad the motor is. I keep you guys updated.


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Got the head off tonight. It is looking a little rough in there.  There is alot of flakes of something in the cylinders and water pump. I have not seen anything like this before. 

This is my first time tackling a seized motor. What would you guys recommend next? I would guess it would need to be soaked. But what would you guys use to soak it? 


Any advice would be greatly appreciated. 


Thanks in advance!




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you can still get new sleeve and pistons sets for 12's a14's, i recomend going that route. The stuff you see in the water pump and coolant elbows is simply big chunk of the insides that have rusted off. pretty typical

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  • 2 weeks later...

I was able to make some good progress. Pulled the block out and got the pistons out , which was way easier than I thought it was going to be. I also pulled the top of the transmission off. Its pretty dirty in there. The oil was very very thick, took about 2 hours for it to drain out. 

Anyone know anything about the over center clutch? I have never even heard of one before. 

What do you guys think about the transmission? Do you think it should be left alone or gone through as well?

I've been having a blast working on this old girl. It's really been going smooth, only broke 2 bolts so far.














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  • 4 months later...

frosty, I just stumbled across your thread just now. By coincidence, I am also restoring an O-12. I bought this tractor from Colin Beamish, also on this site. My wife liked the little tractor, but didn't want to have to hand crank it to start, so I'm rigging up an electric starter for her to use. As I'm sure you know, electric start could be ordered from the factory. The starter motor was tucked in between the oil pan and the left frame of the bathtub casting. The electric start bathtub casting has a offset frame and a bump-out to accommodate the starter motor nose.

After a lot of measuring and testing, I determined a starter motor from an Oliver 77 would fit and work as a starter for the O-12. It turns in the correct counterclockwise direction and has a smaller than normal overall diameter. This tractor has a 1/4" round plate to attach the engine to the bathtub casting. The round plate worked ideal as a template to locate the starter close to the oil pan and align with the ring gear. The ring gear took some trial and error, but finally determined a ring gear from a Allis WD-45 was the perfect diameter. I had a machinist turn a notch into the flywheel to install the ring rear. My local starter/generator rebuilder guy, had to install a 10-tooth, counterclockwise starter drive, as the Oliver starter used the smaller 9-tooth drive.

I though grinding out the bathtub casting would be a big challenge, but again using that 1/4" plate as a template (after the starter was mounted on the plate) made it easy to locate and hole saw a hole for the starter nose clearance. I did some grinding on the inside of the bathtub casting to be sure the front end of the starter didn't touch.

Because this now creates an opening from the outside to the clutch area, I made a little metal box to close out the opening. The only other thing I had to do was drill four holes in the starter motor stout so the starter body could be rotated to make the electrical connection accessible.

The other day I was walking thru the local tractor graveyard and eyeballed a F-12 tractor. It looks to me like the same starter modification might be possible (little more challenging) on an F-12. The clearance measured between the oil pan and the inside of the U-frame was about 4-1/4" and the starter motor is 3-7/8" diameter. This is about the same clearance measured when I started on the O-12!

If this modification is of interest to you, I would be happy to help answer an addition questions or provide more pics.  DonO

starter pic 1.JPG

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starter pic 12.JPG

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