1250 Bad shaking when front PTO engaged

twisties · #1 09-26-2017, 01:32 PM

Hello,

New member and first post. I have a recently acquired 1250 that had been a project for the two previous owners. The person I bought it from did a lot of mechanical work and it appears to be in pretty good shape. My parents had a Cub Cadet when I was growing up, can't remember the model but they got it new in the late 60's. So I'm familiar with them in general, it's just been 35-40 years since I've used one with any regularity.

The only problem that I'm having is that about 9/10 times when I engage the PTO for the mowing deck, the tractor will start shaking/vibrating so bad it will almost stall out. If I immediately disengage the PTO it will continue to shake until I drop the motor speed to idle and then it smooths out. On the rare occasion where the shaking does not occur initially, usually after a few seconds of mowing the shaking will start. There have been instances where it has literally stalled out and will start shaking immediately if I try to start it again.

Just riding around without the PTO engaged it is smooth as silk (well as smooth as expected), no issues whatsoever. Starts right up, idles fine, no weird vibrations, all OK.

After doing some reading here I've done the following: Checked and reset the air gap, it was way too loose/big. Removed the drive belt and checked the bearings and pulleys on the deck, everything rotated easily, per the previous owner he had recently installed new bearings and lubed it. All looked and seemed normal. Reinstalled drive belt, as soon as I started and engaged the PTO same shaking/vibration occurred again.

Took the drive belt off, started it and engaged the PTO, nothing strange happened. Just like running with the PTO disengaged.

Kind of wondering where to go from here. I almost wonder if the bearings in the PTO are bad? It would seem it only happens when the PTO is engaged and under load. Almost all of the time I'm at a dead stop in neutral so I think that rules out any driveshaft or transmission related issues. Any thoughts or suggestions would be welcomed.

Thanks!

I should probably mention that the last owner converted this to a solid mount engine with a beefed up cradle, IIRC he either got the idea here or got parts from someone here but I may be wrong on that. Also has a new flex coupler on the motor side of the drive shaft and the transmission side joint is a U-joint.

olds45512 · #2 09-26-2017, 01:42 PM

Have you checked the blades on the deck? Might have one bent or missing a piece that causing them to be unbalanced.

twisties · #3 09-26-2017, 01:48 PM

Quote:

Originally Posted by olds45512

Have you checked the blades on the deck? Might have one bent or missing a piece that causing them to be unbalanced.

You know, I didn't. I just checked to see if they were spinning freely. When I purchased the tractor I did drive it for about 10 minutes with the deck engaged, appeared to work just fine then and on one instance when I cut for about 10 minutes once I got it home. Have not hit anything with them. I'll have to take a look.

These are noisy and vibrate enough as it is, but it seems like it's coming from up front as opposed to underneath?

olds45512 · #4 09-26-2017, 02:01 PM

If you really believe it's the PTO I suggest removing the grille and starting the tractor and engaging the PTO, look to see if the PTO pulley is running true or is it running out of round. This will help narrow down where the issue is. I shouldn't have to tell you but I will anyway, KEEP YOUR FINGERS AWAY FROM THE PTO.

twisties · #5 09-26-2017, 02:44 PM

Quote:

Originally Posted by olds45512

If you really believe it's the PTO I suggest removing the grille and starting the tractor and engaging the PTO, look to see if the PTO pulley is running true or is it running out of round. This will help narrow down where the issue is. I shouldn't have to tell you but I will anyway, KEEP YOUR FINGERS AWAY FROM THE PTO.

With the drive belt on or off? With it on I have to immediately shut it down, I don't think I could get around there quick enough to see it before it stalled, might have to get a helper.

olds45512 · #6 09-26-2017, 02:48 PM

Quote:

Originally Posted by twisties

With the drive belt on or off? With it on I have to immediately shut it down, I don't think I could get around there quick enough to see it before it stalled, might have to get a helper.

I would do it with the belt on since that's when you really have the issue.