Erratic PTO rotation

[patmac3]

Hi All,
I hope that members may give me an idea of what I need to check out to see if I have a problem here.
Im using a 5 foot finishing mower on the Kioti CK2810 HST.
I bought the tractor a year ago with 50 hours on clock and a warranty that expired in Dec18.
Shortly after buying, the seal at the pto shaft on the tractor was replaced due to slight seepage of oil. Im now up to 100 hours mowing an undulating grass field of 3 acres.
Ive started to notice that after Ive been mowing for say 30 mins the pto shaft intermittently slows.
The deck keeps cutting and the engine revs stay up and travel speed stays constant.
If I disengage and reengage the pto, rotation may start normally or may again rotate slowly.
At present if I see the pto rotating erratically I stop mowing and leave the tractor to cool right down.
Then if I restart all is well until things warm up.
The gears and pto engage and disengage cleanly with no grinding. I only use the clutch for changing gear or engaging/ disengaging pto.
There is no evidence of any fluid leaks.
Whilst the transmission dipstick is a pain to read the level looks satisfactory.
I spoke to my dealer yesterday who said it may be - the clutch slipping when warm ( but engine revs stay up)
or the belt on the mower slipping . The mowing deck was bought new so has done 50 hours.
Ive checked for play on the clutch pedal and it does seem a little restricted so I have asked the dealer to sort that.

As there are so many experienced users on the forum I thought that I would ask for some ideas on diagnosis from others who may have seen this same problem. It will certainly be helpful in my discussions with the dealer!
Many thanks
Pat

 

[mcfarmall]

I'd have the dealer put the tractor on a dynamometer under a full load and watch the PTO rpms. That will tell you a lot. Sounds like the PTO clutch (most likely hydraulic) is slipping internally.

 

[CobyRupert]

Hi All,
....Ive started to notice that after Ive been mowing for say 30 mins the pto shaft intermittently slows.
The deck keeps cutting and the engine revs stay up and travel speed stays constant.
If I disengage and reengage the pto, rotation may start normally or may again rotate slowly.
At present if I see the pto rotating erratically I stop mowing and leave the tractor to cool right down.
Then if I restart all is well until things warm up.
The gears and pto engage and disengage cleanly with no grinding. I only use the clutch for changing gear or engaging/ disengaging pto.
There is no evidence of any fluid leaks.
Whilst the transmission dipstick is a pain to read the level looks satisfactory.
I spoke to my dealer yesterday who said it may be - the clutch slipping when warm ( but engine revs stay up)
or the belt on the mower slipping . The mowing deck was bought new so has done 50 hours.
Ive checked for play on the clutch pedal and it does seem a little restricted so I have asked the dealer to sort that.

If the PTO clutch is slipping the mower rpm's will vary just as erratically as the PTO shaft. Can you hear the mower's rpms (blades, air, etc..) vary with the PTO shaft rpms?
What is confusing is you say the deck keeps cutting.

Excuse this question, but is it just the PTO guard (over the shaft) that you're looking at spinning/not spinning erratically and not the shaft inside it? Does the pto coupling that attaches to tractors PTO shaft vary erratically?

 

[skipperbrown]

I'd hook up another implement that uses the PTO and see how it behaves.

 

[ericm979]

Is there a slip clutch PTO shaft to the mower? Check it's adjustment, it may be slipping.

The CK2810 HST has a live PTO and a clutch between engine and the PTO and transmission. Not a separate PTO clutch. If the clutch is slipping you'd notice that your ground speed is slowing down. If that clutch is slipping you need to fix it right away as replacing it requires splitting the tractor.

 

[CobyRupert]

Is there a slip clutch PTO shaft to the mower? Check it's adjustment, it may be slipping....

Not sure OP's background, so I'll state the obvious:

This is a possibility if the slip clutch is at the tractor end of the PTO shaft near where it connects to tractor.
However, if the slip clutch it at the mower end of the shaft, he shouldn't see the pto shaft intermittently slow.

 

[ericm979]

Not sure OP's background, so I'll state the obvious:

This is a possibility if the slip clutch is at the tractor end of the PTO shaft near where it connects to tractor.
However, if the slip clutch it at the mower end of the shaft, he shouldn't see the pto shaft intermittently slow.

Yep, thanks for clarifying.

Also note that the PTO shaft should have a plastic shield on it. If the shield is not clipped to the tractor with the supplied chain it can rotate with the shaft inside. Sometimes only one end has a chain and the other half will rotate. They often rotate more or less depending on the small amount of friction between the shield and the shaft. That's nothing to worry about.

If the PTO shaft itself is slowing a lot you should feel the mower losing performance and see it in how it cuts.

 

[patmac3]

Many thanks for all comments - they are very helpful. It is the actual pto shaft at the ‘connected to mower end ‘ that I see slowing in rotation. I haven’t stepped off the tractor and looked at the pto rotation at the tractor connection end so will do that.
Eric is correct that it is a live pto with clutch between engine and pto which is why it seems odd that the engine revs don’t vary.
The shield on the pto is only clipped at the tractor. The shield covers about 2/3 to 3/4 of the length of the pto shaft so there is a clear bit of uncovered shaft on view at the mower end. This is the end I can see varying speed of rotation.
Sometimes the slowing is quite substantial - could friction bring the speed of rotation down like this?
Luckily the dealer is only 5 miles away and his mobile mechanic is coming out tomorrow so I have lots of questions I can ask and will report back to the forum with his findings.

 

[Slowpoke Slim]

Does your mower have a slip clutch?

Can you post a pic with the entire pto shaft from tractor to mower gear box in the pic? From the side, so we can see it?

 

[ericm979]

The shield on the pto is only clipped at the tractor. The shield covers about 2/3 to 3/4 of the length of the pto shaft so there is a clear bit of uncovered shaft on view at the mower end. This is the end I can see varying speed of rotation.

The shield is supposed to be full length. It's in two parts. One slides inside the other so the shield is not damaged as the PTO shaft length changes when you raise or lower the implement. Someone would have to have removed the other part of the shield. The uncovered part of the PTO shaft would be a safety hazard for people who got closed to it. All my PTO shaft shields have only one chain, at the tractor end. Sometimes the implement end of the shield turns, sometimes it doesn't. Its easy to stop it turning though so it's not a hazard.

Here's a pic of a PTO shaft with shields intact (it's compressed all the way so you can't see how the shield tube has two diameters):



And here's a PTO shaft without shields: