Manual PTO upgrades, modifications

[Colton Stevens]

I have a 1966 ih cub 71. It has a 12 hp kohler from a 122. I recently got it running and operating for the first time in 30 years. I bought a 38 inch deck from a wide frame, and modified the mule drive and hangar system to work with a narrow frame. Everything is going very well. Worked out most of the kinks with the deck operation but I can't get my mind off the front PTO. When I got it, the triangle spring was broken, therefore pto was inoperable. My brother and I rebuilt the pto with a cub cadet rebuild kit. New pto clutch, triangle spring, coil springs, etc. We struggled getting it adjusted but I am confident that we have it adjusted as correctly as possible now. Our first attempt did not grab hard enough to spin the blades. I did some work to all the mule drive pulleys and spindles etc. And tightened the pto clutch a tad more. The first attempt was based on manufacturer spec with the adjustment tool, but we had to go tighter. I don't want to tighten it further for risk of breaking the triangle. It should be noted that I have the single triangle style, with bent ends.
Now, everything works and the deck cuts grass and things are looking good. However, the blades bog down very easy in medium to tall grass. The motor does not bog down any, the blades just slow down and the pto starts slipping. If I slow the tractor down for a few seconds and let it catch up, the blades speed up and continue cutting.
I know I have plenty of hp and torque to spin the blades better, but the pto cannot grab that hard. There was some resistance in the deck spindles when I bought the deck, but they have significantly gotten better with use and tinkering. Still though, the blades bog down.
I am looking for a solution that either improves the cc design, or proves my user error. I am thinking it would be nice to use the pto to spin the blades up to speed, but then have some sort of lock mechanism that totally prevents clutch slippage once fully engaged. I understand that the clutch is probably designed as an intentional failure point in case the blades lock up, and the motor keeps turning, but I dont really care to be honest.
Any suggestions? Haven't found anything online so far.

 

[kmcconaughey]

Is the tensioner on the spindle belts working property? How tight do you have the drive belt? I would make sure that you have those correct first before spending more time on the PTO.

 

[mfrade]

I'm also curious if you even have the right belt! Width of the belt? Length?
What is the PTO off of?

 

[Colton Stevens]

Is the tensioner on the spindle belts working property? How tight do you have the drive belt? I would make sure that you have those correct first before spending more time on the PTO.

The tensioner on the deck, for the spindle belts does properly tension. I am able to grab it by hand and release the tension and remove the belt without tools however. It feels pretty tight to me but definitely not as tight as like a serpentine belt tensioner on a car. I do notice it rapidly bouncing back and forth during operation, but I didn't think to much of it, or relate it to this problem. I will investigate that avenue further though, but I am fairly certain that I observed the pto moving slower than the rest of the crank while it is bogging down (I had my brother drive while I inspected quickly). Admittedly, I only looked at it briefly.
The drive belt has tension on it but I could go tighter if I need to. Not sure what length the belt is. What I am fairly certain of though, is that I can engage the pto, jam the blades so they dont turn, and turn the engine over by hand using the alternator pulley, and the pto slips before the drive belt. Therefore, I ruled out the drive belt in my mind.
I will see if we still have the package for the drive belt to see what length and width it is.
I assume this pto is from the 12 hp motor, however, I do not have any proof that it did not come from the 7 hp. My understanding is that they would have been the same either way, and the only variation in pto designs is the triangle plate.

 

[Colton Stevens]

Update:
Brother remembers it being a 1/2 in width by 81 in. He said it needs an 81.5 but they only had 81 and 82, so it is a little tricky putting it on. Either way, unless that width seems incorrect to y'all, I can't imagine it would be the problem.

 

[kphill]

Correct me if I'm wrong, but a 122 takes a 3/8 PTO drive belt and most wide frames take a 1/2 belt.. Maybe the belt is not setting all the way in the PTO drive groove..

 

[jkoenig]

Parts lookup says 122 takes a 3/8 x 81.

Good thinking Kevin.

 

[PACub100]

Correct me if I'm wrong, but a 122 takes a 3/8 PTO drive belt and most wide frames take a 1/2 belt.. Maybe the belt is not setting all the way in the PTO drive groove..

My 1450 uses 3/8" belt but I've been using a 1/2" belt since upgrading to a speed-up pulley. I don't have 3/8" available nearby and I haven't ordered a replacement from Digger yet is the only reason I'm not running the 3/8".

Colton, the belt can make a difference. Some of them are really thin. I blew through one in about 10 minutes because it didn't have enough surface area to grab properly. Changed brands to a thicker one and now I can haul down my motor a tad without slippage.

 

[Colton Stevens]

Thanks everyone, I will do some closer observation to 100% verify whether it is a belt or pto slippage issue. I imagine 1/2 belt in a 3/8 pully could maybe even cause it to bund a little and have too much friction, causing unnecessary load and consequently, pto slippage?

 

[PACub100]

Also check your pulley sizes, PTO and center drive. One of them may be too small, might not have enough PTO or belt grip to run the blades that fast.

 

[kphill]

My 1450 uses 3/8" belt but I've been using a 1/2" belt since upgrading to a speed-up pulley. I don't have 3/8" available nearby and I haven't ordered a replacement from Digger yet is the only reason I'm not running the 3/8".

Colton, the belt can make a difference. Some of them are really thin. I blew through one in about 10 minutes because it didn't have enough surface area to grab properly. Changed brands to a thicker one and now I can haul down my motor a tad without slippage.

I guess I should have said the mechanical PTOs take a 3/8 belt and the later electric PTOs take the larger belt..

 

[kphill]

Colton, a V belt transfers the power from the engine to the mower by the sides on the V belt..There is no power transfer on the ends, so if the belt is not making full contact on the sides than you are not getting all the power to the deck, and the belt slips on the PTO...Could also explain why an 81 inch belt seem short and you think you need an 81 1/2...

 

[cmiller]

If you really are slipping the PTO clutch, something is wrong with it. You should easily be able to stall the engine with load (too much grass, too much snow, etc.) and NOT slip at the PTO clutch.

 

[Colton Stevens]

If you really are slipping the PTO clutch, something is wrong with it. You should easily be able to stall the engine with load (too much grass, too much snow, etc.) and NOT slip at the PTO clutch.

Yeah so it is definitely slipping the clutch. I have no idea why. All the clutch components are from a new clutch repair kit from cc, I used the adjustment tool. I adjusted it to factory specs, and even tighter than that. Engine does not stall under any circumstances. It barely changes tone when engaged, but like I said, 12hp motor with a 38 inch deck, so it shouldn't be straining anyways. I see some of the kits online offer two triangles, but those only seem to be with the flat-ended type triangle, mine is the bent tip style triangle. The old triangle was broken on all three tips, so I guess there is a possibility it is the other design, but only one triangle came out of the thing when I took it apart, and it seems to have little impressions on the housing where the bent tips of the triangle fit perfectly. I am afraid to tighten it any more. Maybe I can space it out somehow, and create more tension? Or double up with what is left of my old triangle? Surely it will break if I over tighten it, correct?

 

[mgwin]

There are two types of clutches. A &B. Click on CCSpecialties and then select manual pto's. Scroll down the page and you can see which one you have, and also the correct parts you need. Charlie has some "beefed up" springs with the small tabs on the ends that should work nicely.

 

[bwstevens]

Pictures would be great. a clean single spring clutch will break the belt before slipping in my experience.

 

[bwstevens]

In this picture the left view shows the six jam nuts on the outside of the disk. (nuts jammed together). When the center section is assembled the disk is held tightly then it is placed in the basket.

 

[Steve watley]

Can someone explain why there is a pto with bent finger springs. And the pto with flat finger springs like mine. I just interested in learning about this part as I am replacing mine.

 

[mgwin]

"Bent finger springs" were typically used on narrow frame tractors, but should work on wide frames. "Flat finger springs" were usually on wide frames.
Look on CCSpecialties site, and you can see the differences.

 

[Steve watley]

I seen both. Just wondering why have two types unless one type not so strong. I hear few slipping clothes out there