Farmall Cub Engine Frozen

[ecbrewster]

My 1947 Farmall Cub stalled while idling, seeming to have run out of gas. This was not the case, it had plenty of gas but would not restart. A check of the ignition system showed a very weak spark, so I proceeded to rebuild the magneto.

While attempting to manually re-time the engine by hand cranking, I noticed a slight resistance at one point in it's rotation until several revolutions later, the engine was locked solid and would not turn in either direction.

I have checked the following for the freeze up:
Starter motor, fan, generator, magneto, pto and all are free. This tractor has always been maintained, oil changed, and garaged so that the engine is not seized from rust. What else could it be?

[tst]

Does it have electric start, if so I would pull the starter loose and make sure that it has not jammed the engine, also you could pull the plugs and see if it spins
Tim

[ecbrewster]

I have done both of the above. Thanks for the quick reply.

[Chris D]

Can you put it in 3rd gear and rock it?

[Landreo]

Clutch pushed in, does the engine turn?

[mrdibs]

I just went through this. In my case a chunk of metal was between the piston and the head. When that cylinder reached TDC, it locked up the engine. Couldn't budge it until I loosened the head. Was a relatively small peice of debris that did it. Folks here said it can happen with a hunk of carbon breaking loose, busted ring, whatever. I too had tried everything else first, including rocking it in third.

[ecbrewster]

I have also tried pushing in the clutch,but that didn't change anything. I didn't want to try rocking in gear yet, because I was afraid of doing further damage. I have studuied the Cub service manual in great detail, and reached the conclusion that the drive train is heavy duty and there shouldn't be a gearing problem in the front end, oil pump, or magneto drive.

The best suggestion to date, could be a piece of carbon or foreign material on top of one of the pistons. I'll probably pull the head at my next opportunity, unless I get any other ideas.

Thanks Everyone

[Barnyard]

If you do remove the head you always run the risk of breaking head bolts. Here are a few tips that have proved to be useful.
1. Apply a little penetrating oil such as PB Blaster ahead of time.
2. Use an impact wrench on low pressure and rattle each bolt for a bit
3. Turn the air pressure up a little at a time and alternate from bolt to bolt.

[Eugene]

I have also tried pushing in the clutch,but that didn't change anything. I didn't want to try rocking in gear yet, because I was afraid of doing further damage.

Remove spark plugs, install solvent into cylinders. 3rd gear, rock the tractor backward. Won't hurt a thing since the engine locked up while hand cranking. Once engine frees up gently try the hand crank again. Will probably lock up again.

What else could it be?

Unknown. Can you roll the tractor when transmission is in neutral?

[ecbrewster]

I can roll the tractor in neutral.
Thanks
The loose carbon seems to be the best shot. I once started a 70 Monte Carlo that has sat for several years and had it running when my brother goosed the engine and immediately it developed a loud knock. He thought that he had thrown a rod. We talked to a mechanic who listened and gave it another shot on the accelerator and the carbon blew out and the engine purred like a kitten.

Thanks again

PS Thanksfor the head bolt removal procedure!

[challenger]

If it is something in the cylinder, the engine should rotate backward through a reverse piston stroke until the object again contacts the head. Try to rotate the engine backward, trying, in this order of preference, the fan, while pushing against the fan belt, a screwdriver on the ring gear or carefully rotating a rear wheel slightly backward in third gear while you observe the fan to see if it moves.