Center blade Pulley keeps shearing off z421 kubota

[rick sheltra]

Hello to all
Any suggestions for finding the problem. I have had to replace the center belt pulley twice in one week.
it has just sheared right off at the nut.
I tried to attach pic not sure if it worked.
should the blade mandrel have no wobble in it at all? Could it be maybe hitting rock or something the blade bent and put it off balance and causing the wobbling?
I might add. I have never used the 1.5 “ height setting until this week and both times it broke this pully and the sucker cost 50 $.
am I doing something wrong? Can’t seem to pinpoint the problem.
Any help would be greatly appreciated
Thank you
Rick

 

[lugbolt]

you've got the deck in the dirt at 1.5 setting. Are you turning the blades on while the deck is in the dirt and in tall grass? If so, that can cause issues. Turn the deck on with it all the way up, then drop it down into the dirt.

Hit anything with it? At that low cut height, it's much more likely.

Whats the blades look like?

 

[rick sheltra]

you've got the deck in the dirt at 1.5 setting. Are you turning the blades on while the deck is in the dirt and in tall grass? If so, that can cause issues. Turn the deck on with it all the way up, then drop it down into the dirt.

Hit anything with it? At that low cut height, it's much more likely.

Whats the blades look like?

Hey thanks for the reply yeah that’s how I do it drop it down but I was only cutting grass around the house and wanted to get it low.
Well it doesn’t seem to be scalping the lawn or kicking up dirt however I was going to move the front hard rubber wheels down to where they will work. I don’t think I have ever seen them turn. They came from factory at top position.
For some reason those center pulleys are never in stock so if I can get some extra $ I am going to order a spare. I know I won’t be using that low setting till I figure out how to adjust the rest of it!
I cut the fields with 4-5 “ at a slow even pace and it has worked well at that height. But the 1.5 -2” even on smooth grass just seeemed to cause problems.
so now I think I need another shaft which means bearings and shaft maybe 40$ the whole pulley holder is 90 which I assume is the complete assembly. I found a pulley 40 miles from here but no shaft or pulley holder complete yet. I Thought they were called mandrels but kubota refers to them as Pully holders
Anyway yeah blades are nicked need replacing. When I had it standing up the blades leaned slightly to one side when free from
The belts which I would think indicates it’s bent. So would it be correct to assume shaft is bent and wobbling and causing the center nut to heat up and come off? Thanks so very much for any advice I certainly appreciate it

 

[lugbolt]

Hey thanks for the reply yeah that’s how I do it drop it down but I was only cutting grass around the house and wanted to get it low.
Well it doesn’t seem to be scalping the lawn or kicking up dirt however I was going to move the front hard rubber wheels down to where they will work. I don’t think I have ever seen them turn. They came from factory at top position.
For some reason those center pulleys are never in stock so if I can get some extra $ I am going to order a spare. I know I won’t be using that low setting till I figure out how to adjust the rest of it!
I cut the fields with 4-5 “ at a slow even pace and it has worked well at that height. But the 1.5 -2” even on smooth grass just seeemed to cause problems.
so now I think I need another shaft which means bearings and shaft maybe 40$ the whole pulley holder is 90 which I assume is the complete assembly. I found a pulley 40 miles from here but no shaft or pulley holder complete yet. I Thought they were called mandrels but kubota refers to them as Pully holders
Anyway yeah blades are nicked need replacing. When I had it standing up the blades leaned slightly to one side when free from
The belts which I would think indicates it’s bent. So would it be correct to assume shaft is bent and wobbling and causing the center nut to heat up and come off? Thanks so very much for any advice I certainly appreciate it

couple things
if the blades are worn, they become out of balance. Vibration will loosen everything and will also take out the deck bearings prematurely. Possibly even loosen up the nut on the spindle shaft too. For that reason I bought a precision blade balancing jig and check them all. Even brand new blades are out of balance sometimes, and I've had to grind them and paint them (brand new). It's crazy.

on the deck wheels. They should be about 1/4-1/2" off the ground with the deck at desired cutting height. They are shipped on a reusable crate and when they place the mower onto the crate, they drop the deck as low as it will go, and with that-they also move the wheels up as high as they'll go to keep them from getting beat up with the tech drives it off the crate. Most of the time the setup techs don't readjust the wheels because they don't know what the end user's cut height is going to be. Some guys like to cut at 3" exclusively and some like to cut dirt.

for those that might have interest, below is the balancer I bought-unfortunately the price has doubled in the last year. I paid $48 for it. When using this tool, make SURE your fingers aren't between the magnets and the blade because if they are, you're fixing to get a bruise. Those magnets are stout!

Amazon.com

 

[rick sheltra]

couple things
if the blades are worn, they become out of balance. Vibration will loosen everything and will also take out the deck bearings prematurely. Possibly even loosen up the nut on the spindle shaft too. For that reason I bought a precision blade balancing jig and check them all. Even brand new blades are out of balance sometimes, and I've had to grind them and paint them (brand new). It's crazy.

on the deck wheels. They should be about 1/4-1/2" off the ground with the deck at desired cutting height. They are shipped on a reusable crate and when they place the mower onto the crate, they drop the deck as low as it will go, and with that-they also move the wheels up as high as they'll go to keep them from getting beat up with the tech drives it off the crate. Most of the time the setup techs don't readjust the wheels because they don't know what the end user's cut height is going to be. Some guys like to cut at 3" exclusively and some like to cut dirt.

for those that might have interest, below is the balancer I bought-unfortunately the price has doubled in the last year. I paid $48 for it. When using this tool, make SURE your fingers aren't between the magnets and the blade because if they are, you're fixing to get a bruise. Those magnets are stout!

Amazon.com

Thanks thats great info. I think I am going to try and get the complete pully holder in case the shaft is bent or bearings are bad. Going off to read about the balancer. I try to cut it usually at 3" this was the first time I used the 1.5 setting and those front wheels are so high up they dont touch. As soon as it stops raining here Ill be back to mowing thanks again

 

[rick sheltra]

A year later no problems cutting at 3" however wonder why they put the setting on the mower if you cant use it. anyway here is something i did not like about the new kubota. when i finally replaced bearings they were marked "MADE IN CHINA" how sad...a once proud japanese company cheaped out on the bearings. I wrote to them to express my dismay at their choices. Im sure it made no difference. I have had to replace the bearings twice. No Japanese ones are available . The 1970 or so B7100D i bought used 25 years ago, is frigging incredible. I have never seen such a workhorse as this rice paddy tractor
Orange tractor talks VIC kept me going for years and now the WOLFMAN love having access to all this knowledge much appreciated.

 

[Henro]

Curious.

Bearings are made in a lot of different countries, and high quality too. What is the issue? No number on either the the bearings you have or the old original that failed? I would think with a number it would be fairly easy to cross reference and buy a quality replacement.

Just wondering. I don't buy bearings often...I did last summer though, for the mower deck on my BX. Cheap Chinese (I assume) off Ebay. Worked for a few months until the grass stopped needing cut due to the white dandruff stuff falling. I don't expect miracles out of those bearings, but so far so good.

 

[Joisey]

I'm not familiar with that mower, but you stated that the nut that holds the pulley in place backed off? If so, and it is self locking, sometimes those nuts are only good for one use because they lost their holding power. Blade vibration will easily back them off. Good luck

 

[GreensvilleJay]

The nuts/shafts are all fine thread, never seen lock nuts on any of the zillion riders over the decades..
One problem is people NOT aligning the blade 'notches' onto the spindle 'tabs' so that the blade is PROPERLY seated, flush onto the spindle. Since the blade isn't 'locked' onto the shaft, it 'll go 'wonky' and bad things happen...... costly bad things....

 

[lugbolt]

The nuts/shafts are all fine thread, never seen lock nuts on any of the zillion riders over the decades..
One problem is people NOT aligning the blade 'notches' onto the spindle 'tabs' so that the blade is PROPERLY seated, flush onto the spindle. Since the blade isn't 'locked' onto the shaft, it 'll go 'wonky' and bad things happen...... costly bad things....

if one has any common sense, that will be totally obvious when the blades are turned on. The vibration will shake your teeth out, and probably the neighbor's too.

back to broken spindle pulleys. Had a few of them over the past summer and every single time the blade was out of balance, usually horribly. One case, I put new blades on in the spring time for him, 16 hours of use later he's got a busted pulley. I peek under the mower and the blades are GONE. I mean the wings are completely worn off and the cutting edge is so dull that the worn back edge where the wings used to be is much sharper. I thought about just flipping them over and sending it....but we came to the conclusion that he is mowing in 1.5" setting, and his yard is nothing but river silt with a few blades of grass growing in it which he mows twice a week whether it needs it or not. That thing had to vibrate terribly. The entire underside of the deck had zero paint left on it. Air filter completely plugged. Guy said he never had to use the choke. The plugged air filter does the choking for him. I had it on my lift and showed him and he asked my suggestion. "Roundup".

 

[GreensvilleJay]

re: if one has any common sense, that will be totally obvious when the blades are turned on

you'd think so..but 'they' never clean the wet grass off the bottom of their decks either !!!

my suggestion.... Astroturf