Starting question i havent found the answer to

[48farmallAz]

hey guys newbie here. sorry if this question has been answered, i couldnt find anything related. so sorry again if its a repeat question.

I have a 1948 cub 6 volt. i was out mowing my pastures for about an hour and when finished i put it in a higher gear to head back to the barn. it started bogging down and eventually died. i tried to restart it and it sounded like the battery was dead or not enough juice to crank, when it did try there was a loud knocking sound from the fan pulley. i went and recharged the battery and the next day it started right up. still had a knock from the fan pulley area. put it in a high gear and started bogging down again so put it in first and drove just fine. got to my gate and after opening it i put it in first and then it died.
I know my battery was real old and even tho i was getting 6v i still took it to have it checked. one place said good and another said bad. so i went ahead and bought a new one. the issue im having when trying to start is it sounds like a bad battery. i pull the lever to start it and you hear the knock from the cranking motor and thats it. no attempt to start or a crank or anything. just the simple knock when you pull the starting lever and silence. the fan does kick about a 1/4 inch everytime the lever is pulled. before driving it just in idle everything sounded and looked fine (minus that knock from the fan pulley) i feel like its an electrical issue somewhere and not so much mechanical since it ran just fine when mowing. i am getting 6v at the switch as well. but even to bypass the switch im not sure where to hook the wire too.
Sorry such a long post but i am stumped. any info would be great on whats going on. i have youtube and googled it but seems all the starting issues the tractor at least cranks, which would be a little easier to troubleshoot if mine at least did that. Thank you again.

[John *.?-!.* cub owner]

A couple questions. Does it still have magneto, or has it been converted to a distributor. If distributor, low battery voltage can cause weak spark and low power. As to the knock that is hard to diagnose without being there. How is oil pressure?. If low oil pressure could be a fron connecting ord, or could be bad fan bearing and blades hitting something, Need to take fan belt off and run it briefly to see if still has knock. That will answer several questions.

[48farmallAz]

It is still magneto, I believe. If I’m looking at it right. Nothing has been converted. I believe the oil pressure is low, if my gauge is working properly. I will take the fan belt off and see what happens once I get it to crank. Thank you for the info

[Jim Becker]

Take the fan belt off now and see if it will crank.

[Urbish]

Do you have a hand crank? See if you can hand crank it when it bogs down. And like the others said. Pop the belts off and see if the fan and generator turn without effort.

[48farmallAz]

Thank you for the info. I will try that this afternoon

[MiCarl]

Speaking from experience with a 1948 Cub:

Even with a good battery the starter will crank like you have a dead battery if there is even just one less than perfect connection in the starting circuit. When they're all good the starter spins so fast it's a wonder it doesn't flip the tractor. That single knock you hear with the new battery could well be the sound of the starter engaging and then the extra amps cause that poor connection to fail completely.

[staninlowerAL]

Do you have a hand crank? See if you can hand crank it when it bogs down. And like the others said. Pop the belts off and see if the fan and generator turn without effort.

Agree with Urbish on hand cranking. Your info about the magneto system indicates that you should be able to hand crank/start and run the engine without using the battery since a magneto creates its own electrical power to start/run the engine.

[48farmallAz]

I don’t have a hand crank specifically for the tractor but took one from my Model A and seems to fit. But it won’t turn at all. Slips going clockwise and won’t turn going counterclockwise. May be just wrong crank. Working on getting the fan belt off to see if it will crank with out it. But the hood screws haven’t been removed in 50 years so a little stuck! Hopefully today they will break free and I can get the belt off.

[Urbish]

Here's hoping it is the fan or generator that is siezed and not your engine!

[Urbish]

You should also be able to gently turn the fan blades with your hand and get the engine to turn over OR get the belt to slip to confirm that the fan hub is free, without removing the hood. Make sure your ignition is turned off (I always pull coil wire too, just to be safe) so it doesn't fire up and injure you.

[48farmallAz]

Thank you! I tried to spin the fan by hand and it’s real tough. But I can spin it slowly.

[48farmallAz]

So I removed the fan belt and still same issue. The fan billet and generator both spin free. Still can’t hand crank it. Could a bad starter be an issue? Is it possible for a motor to seize right after riding it for an hour?

Also I have no oil pressure but not sure if it’s cause I changed the oil while I was letting the battery charge. I know before all this happened it was low but still had pressure. Haven’t primed it yet.

[MiCarl]

Pull your starter and look at the ring gear on the flywheel. See if it's all chewed up.

I haven't heard of it happening on a Cub but a worn ring gear on some other IH tractors can cause the starter to jam in it. That locks the engine up tight.

Once you've checked the ring gear try your hand crank again.

[Eugene]

Pull your starter and look at the ring gear on the flywheel. See if it's all chewed up.

I haven't heard of it happening on a Cub but a worn ring gear on some other IH tractors can cause the starter to jam in it. That locks the engine up tight.

Once you've checked the ring gear try your hand crank again.

Put tractor in 3rd gear and rock, hard, a couple of times the tractor. Normally this will free up a stuck starter. Then try the hand crank.

Tractor out of gear, see if it will roll a bit. Just checking to see if the transmission gears are jambed.

Is it possible for a motor to seize right after riding it for an hour?

Yes. Very low or no oil pressure will take out a crankshaft bearing or two and possibley lock up an engine.