C-120 Clutch not engaging

[oldhorse2 3]

I am the original owner of a C-120 (purchased in 1996). Yesterday, after mowing and then stopping the mower, I attempted to restart the mower by actuating the PTO lever and the mower didn't start. The mower belt turned freely by hand, but apparently the drive disk wasn't engaging. I adjusted the trunnion (about 2-3 turns) until I got some engagement, and the mower ran intermittently. I haven't disassembled the PTO yet, but am wondering if this is usually caused by worn/missing lining or something?

 

Correction - I bought the tractor in 1976

[oliver2-44 8,875]

If the PTO belt was turning, but the blades weren't turning or were intermittent, You might check the tensioner  bar down on the mower deck.  The tensioner bar has hard plastic sliders that wear out and the slot in the steel bar can wear. 

You can get the plastic sliders from one of the vendors, Wheel Horse Parts and More.

 

If you clip pins in the PTO yoke, you can then slide the complete PTO pulley bell off to get a good look at the clutch disk.  If the clutch material is above the rivets, its still good.  Give the needle bearing in the PTO bell a small amount of new grease before reinstalling.  not to much or it will sling out on the clutch. 

[oldhorse2 3]

Thanks for your suggestions guys. I'll let you know how I make out.

[Lee1977 6,249]

Check the C-clip in the short shaft that attached to the loop. If it come out of the groove you can't keep the clutch adjusted. I have had to replace that short shaft a couple of times in the last 44years.

Also check the outer PTO bearing they wear out to, replaced a couple of them.

Edited August 13, 2023 by Lee1977

[oldhorse2 3]

I pulled the PTO housing off today and examined the interface between the drive shaft and the stub shaft. Clearly something broke. I have a Service manual with parts diagram, but am still unclear what needs to be replace. I haven't been able to locate any photos of this. Any help would be appreciated. 

[Gasaholic 183]

17 minutes ago, oldhorse2 said:

I pulled the PTO housing off today and examined the interface between the drive shaft and the stub shaft. Clearly something broke. I have a Service manual with parts diagram, but am still unclear what needs to be replace. I haven't been able to locate any photos of this. Any help would be appreciated. 

 

Your center stub screw backed out. That screw was meant to hold the thrust bearing & spring set in place (There'd be a thrust washer, flat roller thrust bearing, another thrust washer, and a spring that slip over that center screw, which was slotted to thread it in.) When that happened, your stub shaft was hitting the screw which may have prevented your clutch from fully engaging (or your clutch face worn out, or drive pulley on too far - but that'd throw drive belt out of alignment- or your stub shaft bearing seat in the clutch pulley stack wallowed out deeper from bearing being frozen, among other things)  So, if your stack pulley is fine, clutch facing is fine, then I'd probably recommend:  1) new stub screw, new thrust waher (a pair), new thrust bearing (goes between washers) new thrust spring, new stub shaft (IF that old one goes back in, it'll just tear up the spring) new snap rings for stub shaft (2) and new stub shaft bearing and internal snap ring.  

 

Edit to add: And actually looking at your photo, seems like your drive pulley might be a little too far on to the crankshaft - a 1/16th of an inch or so- most of them the inner race for the PTO (which butts up against the pulley) would sit flush or slightly proud of the end of the crank... might have to check your drive belt alignment and/or add a shim on the engine side of drive pulley? 

Edited August 15, 2023 by Gasaholic
addition.

[oldhorse2 3]

Thanks for the analysis. Any suggestions as to where I can find the part #s, and a possible source for the parts?

[Gasaholic 183]

I believe there's parts manuals here in the Manuals section (You'd have to root around in there to find the manual for your machine, probably need the model number off the Serial number tag) 

 

Being a C-120, you would ONLY use those thrust bearing parts if the machine is equipped with a PTO Brake - If your tractor DOES NOT have PTO brake, then just remove that center screw and discard it as the thrust parts will not be used or needed.  (BUT, I'd still suggest checking drive belt alignment, as well as replacing stub shaft & Snap rings & Bearing.) 

 

 

[8ntruck 6,400]

I believe that the stub shaft, snap rings, and bearings are still current parts at a Toro dealer.

[gwest_ca-(File Mod) 10,513]

If you change the outer bearing stub shaft with a late version that has two retaining rings you can eliminate the inner parts. The outer bearing ends up between the retaining rings so when the pto is disengaged the rod pulls the pto bell away from the friction plate.

https://www.partstree.com/models/31-12k801-312-8-toro-garden-tractor-1990/pto-clutch-and-control-47/

You need one of 33 and two of 34

[oldhorse2 3]

Just now, gwest_ca said:

If you change the outer bearing stub shaft with a late version that has two retaining rings you can eliminate the inner parts. The outer bearing ends up between the retaining rings so when the pto is disengaged the rod pulls the pto bell away from the friction plate.

https://www.partstree.com/models/31-12k801-312-8-toro-garden-tractor-1990/pto-clutch-and-control-47/

You need one of 33 and two of 34

The PTO shaft in my tractor does have 2 snap rings. Apparently they still used the inner parts that caused the problem. It also has the brake bracket. I wonder if I should just eliminate that and the other parts you mentioned?

[Gasaholic 183]

1 hour ago, oldhorse2 said:

The PTO shaft in my tractor does have 2 snap rings. Apparently they still used the inner parts that caused the problem. It also has the brake bracket. I wonder if I should just eliminate that and the other parts you mentioned?

You CAN, but not necessarily SHOULD. It would work without the thrust spring, washer, bearing & screw, HOWEVER the performance of the PTO Brake (and also the ability for the PTO to quickly disengage) will not be up to par. That is, assuming you actually have a PTO Brake (and not just the bracket for it - The PTO bracket for brake equipped units has the 2 square holes for carriage bolts that the PTO brake itself bolts to. It wasn't original to the earlier models, I believe - my 1974 C-100 does not have that - , but it can be installed from a later model, often if it had an engine swapped in from a newer horse.) 

 

While you have it apart, ALSO check the big roller bearing in the PTO (and the recess between it and the Ball Bearing/Stub Shaft) because you likely have a bunch of gritty crud that, if it gets into your roller bearing, will quickly rip it to shreds, and then you'd have to replace the roller bearing (Which can be a PITA if you do not have a shop press to press out & install the press-fit roller bearing & seal)   

Edited August 15, 2023 by Gasaholic

[oldhorse2 3]

Problem resolved! I replaced the stub shaft ball bearing and Spirol pin, and all seems to be fine now. Thanks for all of your help.