Kubota GR 2120 blade problem

[Jimongee]

Hi, I’m Jim and I’m new to this forum. I have Kubota GR2120 54” deck. I purchased it 4 years ago. It has done a pretty good job until this season when it started missing a 2” strip. Ok so that is the small problem. Yesterday I was mowing and for no reason suddenly a loud rotational banging from under the deck. It sounded maybe worse than 911! Ok so I shut it down and raised the deck and expected to find a big contact witness mark somewhere on the deck housing. Instead I found a slightly bent blade. So I installed a new blade and started it up and engaged the blades. For about 2 seconds all sounded normal. And then the horrific noise again. So I removed the deck and hung it in my shop for easy inspection. I’m a former automotive technician who still works on everything. Ok so I found that the right blade tip was contacting the center blade tip. This apparently occurred every time the rotation sequence brought the respective tips together. So I assumed somehow a loose or bent spindle. First I made sure all spindle mounting bolts and washers were 100 % tight and no evidence of movement on the net mounting holes. Additionally I straight-edged the desktop side for distortion..found none. Then with the deck hanging and the belt off I used a welding marker and made an index line on the deck housing and then rotated each respective blade 180 expecting to find a bent spindle. All were perfect. Next I measured the distance between the center of the R spindle to the center spindle and got 18.75” When I did the same on the L side it was 19’. So next I removed all 3 spindles, checked the bearings and put each one in my vice and checked for trueness. Found zero distortion. So I’m stumped! I realize I could grind a small slice off the ends of the right blade to provide contact clearance. But I’m going nuts trying to problem solve how could this machine cut per for 3 years and suddenly blade to blade contact and a uncut strip of grass. I know this is a long msg, but I need your help here. Thanks. Jim in Franklin,N

 

[eddieirvine]

I am confused to not sure how your belt system is set up or pulleys? did you hit something that could have bent one of the shafts on your pulleys? your measurements could come out ok but shaft on the bottom side of your deck could be bent?

 

[Mike1955]

Hi, I’m Jim and I’m new to this forum. I have Kubota GR2120 54” deck. I purchased it 4 years ago. It has done a pretty good job until this season when it started missing a 2” strip. Ok so that is the small problem. Yesterday I was mowing and for no reason suddenly a loud rotational banging from under the deck. It sounded maybe worse than 911! Ok so I shut it down and raised the deck and expected to find a big contact witness mark somewhere on the deck housing. Instead I found a slightly bent blade. So I installed a new blade and started it up and engaged the blades. For about 2 seconds all sounded normal. And then the horrific noise again. So I removed the deck and hung it in my shop for easy inspection. I’m a former automotive technician who still works on everything. Ok so I found that the right blade tip was contacting the center blade tip. This apparently occurred every time the rotation sequence brought the respective tips together. So I assumed somehow a loose or bent spindle. First I made sure all spindle mounting bolts and washers were 100 % tight and no evidence of movement on the net mounting holes. Additionally I straight-edged the desktop side for distortion..found none. Then with the deck hanging and the belt off I used a welding marker and made an index line on the deck housing and then rotated each respective blade 180 expecting to find a bent spindle. All were perfect. Next I measured the distance between the center of the R spindle to the center spindle and got 18.75” When I did the same on the L side it was 19’. So next I removed all 3 spindles, checked the bearings and put each one in my vice and checked for trueness. Found zero distortion. So I’m stumped! I realize I could grind a small slice off the ends of the right blade to provide contact clearance. But I’m going nuts trying to problem solve how could this machine cut per for 3 years and suddenly blade to blade contact and a uncut strip of grass. I know this is a long msg, but I need your help here. Thanks. Jim in Franklin,N

Jim. I never had blades to touch. I have had a three blade finish mower start cutting uneven. I tried everything. I never got it right nor do I know what happened. Can’t help you but I understand your grief on this

 

[dodge man]

My guess is a bad spindle. It probably looks ok but under load at speed it wobbles.

 

[Jimongee]

Thanks Dave but the blades contact each other even with the mower off and rotated by hand. I rolled the spindles in the vice with an indicator and all 3 are totally true. This is a big mystery. My current solution which I’m not happy about is I ground a fat 1/16” off of each end of the R blade and now I’m mowing the lawn like normal. That does not explain how this occurred. Still thinking….
If anyone has a gr2120 out there and could provide the exact measurement center to center between the R and center spindle and left and center spindle that would be great. Mine are off by 3/8”. Doesn’t make sense….

 

[Gordon Gould]

I know nothing about your mower but my JD mower has a timing belt and if I hit something hard enough the spindle can slip on the belt and cause the blades to hit. Just wondering.

gg

 

[dodge man]

The only thing I’ve got since thinking about this is the wrong blades. Are they Kubota blades? My thought is out of luck the blades were aligned where they weren’t touching then a belt slipped a little bit and then they started touching. That seems like the only thing it can be.