Z231KW-42 - Increasing vibration problem causing deck pulley bearings to wear out prematurely

[Farmersfarmer]

Purchased a Z231KW-42 in 2021 to maintain a vacation property that we own with a .3 ac lot. The mower began demonstrating a vibration that steadily increased until the mower deck pulleys and idler arm wore out at only 8 hours of operation. Warranty covered the parts/labor and sent me on my way.

The vibration once again appeared and was prominent at 20 hours and began growing worse. This time it caused all of the deck pulley bearings to prematurely wear out, idler arm, tensioner pulley and bracket, spindles and other deck parts to include new blades were all replaced. The dealer reached out to Kubota and had their technicians get involved. In all, 23 items related to the mower deck were replaced attempting to locate the origin of the vibration. Released the mower to me once again and after two lawn cuts the vibration was detected yet again.

The vibration is non-constant with an alternating pattern of about 5 seconds between smooth operation and then a vibration period of roughly the same timeframe strong enough that it causes the ROPS to shake vigorously before disappearing again. The vibration is there at idle without the PTO engaged and becomes masked when the mower deck is engaged and rpms are increased to operational speed, but you can still detect the alternating vibration pattern when seated on the mower and by viewing the ROPS. Its presence without the deck engaged would suggest to me that something related to the engine or its positional mount to the frame itself would have to be involved because nothing else is in motion at that point in time. Yet the engine was apparently cleared of any problems or concern.

Has anyone else who owns a Kubota Zero-turn, particularly a Z231KW-42 or other 200 series, experienced similar vibration problems that caused multiple failure of moving mower deck parts in a pattern described above?

 

[GreensvilleJay]

yeesh, this is a 'head scratcher' !!!
I'd REMOVE the vbelt driving the deck and then go for a 'test drive'. If there's ANY vibration like the 5 seconds rough, 5 fine, then it HAS to be 'driveline' related.

Curious, does the vibration occour while NOT moving ? if so then kind points to 'engine'.

If it's 2 cylinder gas....does it have 'electronic' magnetos ? had a Cub Cadet with them..terrible units..Cub had a replacement 'kit' that had 2 NORMAL mags.

 

[Yooper]

Watching this one. Sorry, not the owner of one but this is pointing towards resonance (aka sympathetic vibration). An engineer’s worst nightmare. The fix is either changing the material it is made out of or adding or subtracting existing material to change the natural frequency. Hopefully it is something more simple

 

[SDT]

Purchased a Z231KW-42 in 2021 to maintain a vacation property that we own with a .3 ac lot. The mower began demonstrating a vibration that steadily increased until the mower deck pulleys and idler arm wore out at only 8 hours of operation. Warranty covered the parts/labor and sent me on my way.

The vibration once again appeared and was prominent at 20 hours and began growing worse. This time it caused all of the deck pulley bearings to prematurely wear out, idler arm, tensioner pulley and bracket, spindles and other deck parts to include new blades were all replaced. The dealer reached out to Kubota and had their technicians get involved. In all, 23 items related to the mower deck were replaced attempting to locate the origin of the vibration. Released the mower to me once again and after two lawn cuts the vibration was detected yet again.

The vibration is non-constant with an alternating pattern of about 5 seconds between smooth operation and then a vibration period of roughly the same timeframe strong enough that it causes the ROPS to shake vigorously before disappearing again. The vibration is there at idle without the PTO engaged and becomes masked when the mower deck is engaged and rpms are increased to operational speed, but you can still detect the alternating vibration pattern when seated on the mower and by viewing the ROPS. Its presence without the deck engaged would suggest to me that something related to the engine or its positional mount to the frame itself would have to be involved because nothing else is in motion at that point in time. Yet the engine was apparently cleared of any problems or concern.

Has anyone else who owns a Kubota Zero-turn, particularly a Z231KW-42 or other 200 series, experienced similar vibration problems that caused multiple failure of moving mower deck parts in a pattern described above?

Not familiar with your model.

Sounds like a resonance issue.

Gasoline or diesel?

 

[Farmersfarmer]

yeesh, this is a 'head scratcher' !!!
I'd REMOVE the vbelt driving the deck and then go for a 'test drive'. If there's ANY vibration like the 5 seconds rough, 5 fine, then it HAS to be 'driveline' related.

Curious, does the vibration occour while NOT moving ? if so then kind points to 'engine'.

If it's 2 cylinder gas....does it have 'electronic' magnetos ? had a Cub Cadet with them..terrible units..Cub had a replacement 'kit' that had 2 NORMAL mags.

Well, It's under full warranty so I'm hesitant to remove belts or tamper with it in any other manner while it's being evaluated by Kubota. The vibration is there when the mower is not moving so it would definitely suggest that the engine itself has some type of internal balance issue or the engine is causing the frame to somehow vibrate in a manner that is transmitted to the mower deck parts. Not certain regarding the magnetos.

thx.

 

[Farmersfarmer]

Watching this one. Sorry, not the owner of one but this is pointing towards resonance (aka sympathetic vibration). An engineer’s worst nightmare. The fix is either changing the material it is made out of or adding or subtracting existing material to change the natural frequency. Hopefully it is something more simple

Your description is more what I was attempting to relay in my original post. It definitely demonstrates the premise of an amplified resonance throughout the frame that is arising from the engine in motion. In my own words, it was what I was attempting to try and explain to the Kubota corporate folks and to let them know that something in the fundamental manufacture of the mower constituted the origin and since the frame itself could be to blame then replacement of the mower itself was the most expedient solution that would finally permit me to move ahead absent any further problems in that regard.

Thx for the reply.

 

[Farmersfarmer]

Not familiar with your model.

Sounds like a resonance issue.

Gasoline or diesel?

It's a Kawasaki gasoline model. I had checked around with other owners who stated that the Kawasaki was hands down a better option than the Kohler option that also came standard with this particular mower. I had no other frame of reference by which to judge which was best, so I opted for the Kawasaki.

I will say here that when placing your hand on the top of the engine while it runs at idle, you can only detect a smooth operation of the running engine. You have to view and place your hand on the ROPS or other part of the mower's frame to sense the alternating vibration or "resonance" that was mentioned in your post and to a greater extent in another reply.

thanks for the input.

 

[jaxs]

Your description is more what I was attempting to relay in my original post. It definitely demonstrates the premise of an amplified resonance throughout the frame that is arising from the engine in motion. In my own words, it was what I was attempting to try and explain to the Kubota corporate folks and to let them know that something in the fundamental manufacture of the mower constituted the origin and since the frame itself could be to blame then replacement of the mower itself was the most expedient solution that would finally permit me to move ahead absent any further problems in that regard.

Thx for the reply.

That is exactly what I would do at this point. Send dealer certified letter demanding a new Z-turn withing 10 days and if not you will buy a different brand from a different dealer then pursue refund of what I paid dealer plus compensation for having to beg,borrow,rent and steal mowers while the one in question was in shop.

 

[lugbolt]

blades are known issues on the 42" units

even brand new blades out of the box are often out of balance, sometimes severely. Very inconsistent. But I can't think of a single "set" that wasn't out of balance.

Great little mower-once the blades are correctly balanced, and those little benchtop balancer things are not the way to do it-those are rarely even close to accurate. I use a precision blade balancer that is screwed to the wall, magnetic deal on it holds the blade on a cone. Then you turn it horizontal, if one side is light the heavy side falls.

with two blade 42" deck, the blades are 21 1/2" long (give or take),

balancing is as much the weight difference at each side as it is how far away from center the weight is. So the longer the blade, the more critical they are to balance properly-which is why the twin blade 42" decks are VERY sensitive to this, IMO.

So you may mention this to your dealer. I learned the hard way. One other thing I learned is that Kubota just kept sending out those 42" blade sets and nothing really changed when I was there, even after multiple warranty claims showing them out of balance. It was to the point where I was simply pulling them off of new mowers, and balancing them (grinding), then repainting them to "look new" after grinding/balancing. Brand new. Never got paid any labor for doing it either, it was just a service I did for customers so that they didn't show up a week later madder than a wet hen about their expensive lawn cutter vibrating. What was odd was that after doing a dozen sets, and filing warranties on them, they only paid maybe two. The rest of the time they just denied them saying "not a manufacturing defect". I beg to differ.

 

[jaxs]

blades are known issues on the 42" units

even brand new blades out of the box are often out of balance, sometimes severely. Very inconsistent. But I can't think of a single "set" that wasn't out of balance.

Great little mower-once the blades are correctly balanced, and those little benchtop balancer things are not the way to do it-those are rarely even close to accurate. I use a precision blade balancer that is screwed to the wall, magnetic deal on it holds the blade on a cone. Then you turn it horizontal, if one side is light the heavy side falls.

with two blade 42" deck, the blades are 21 1/2" long (give or take),

balancing is as much the weight difference at each side as it is how far away from center the weight is. So the longer the blade, the more critical they are to balance properly-which is why the twin blade 42" decks are VERY sensitive to this, IMO.

So you may mention this to your dealer. I learned the hard way. One other thing I learned is that Kubota just kept sending out those 42" blade sets and nothing really changed when I was there, even after multiple warranty claims showing them out of balance. It was to the point where I was simply pulling them off of new mowers, and balancing them (grinding), then repainting them to "look new" after grinding/balancing. Brand new. Never got paid any labor for doing it either, it was just a service I did for customers so that they didn't show up a week later madder than a wet hen about their expensive lawn cutter vibrating. What was odd was that after doing a dozen sets, and filing warranties on them, they only paid maybe two. The rest of the time they just denied them saying "not a manufacturing defect". I beg to differ.

Good reason for op to bail out when he still can and not risk future "not a manufacturing defect" issues. If a dealer can't fix issues while under warranty don't you know they will drain your bank account when it's at owner's expense?

 

[whitetiger]

Check to see if there is a piece of wood or debris stuck in the seam of the clutch pulley, we find this a lot.

 

[GeoHorn]

That is exactly what I would do at this point. Send dealer certified letter demanding a new Z-turn withing 10 days and if not you will buy a different brand from a different dealer then pursue refund of what I paid dealer plus compensation for having to beg,borrow,rent and steal mowers while the one in question was in shop.

Well, THAT will certainly elevate the issue to a known place quickly.

 

[GreensvilleJay]

this....
The vibration is there at idle without the PTO engaged
... would seem to indicate it's NOT an unbalanced blade issue, or something stuck in the E-PTO unit

which is why I suggested removing the deck drive belt from the E-PTO. something everyone will do at some point and doesn't void the warranty.

if the vibration is still there, it's NOT a 'deck issue' and eliminates a lot of parts.

the 'comes and goes' every 5 seconds is interesting.

easy test.... remove gas cap or back off 3-4 turns, startup and run the machine, does it run properly or still vibrate ?

 

[DaveFromMi]

This sounds like a "beat" frequency. There are a couple of rotating parts where the vibration/vibration order are almost lined up. When the parts vibrations or vibrations order line up, you get a "beat*.

The FFT - Page 21

 

[SDT]

That is exactly what I would do at this point. Send dealer certified letter demanding a new Z-turn withing 10 days and if not you will buy a different brand from a different dealer then pursue refund of what I paid dealer plus compensation for having to beg,borrow,rent and steal mowers while the one in question was in shop.

Good luck with that.

SDT, Esq, JD

 

[SDT]

Well, It's under full warranty so I'm hesitant to remove belts or tamper with it in any other manner while it's being evaluated by Kubota. The vibration is there when the mower is not moving so it would definitely suggest that the engine itself has some type of internal balance issue or the engine is causing the frame to somehow vibrate in a manner that is transmitted to the mower deck parts. Not certain regarding the magnetos.

thx.

Agreed.

Don't tamper with things while under warranty.

Manufacturers representatives, Kubota and otherwise, will look for opportunities to deny claims.