Kubota B2650 and Snow Blower B2781B Tensioner for PTO Gear box keeps breaking

[mholka]

Okay I am having issues and the dealership has not been able to figure this out either.

I have a kubota B2650 and Snow Blower B2781B. There is a bolt in the side of my PTO gear box that is used to provide tension on the sprocket to keep the chain tight. And it keeps breaking. I had this happen last season (its 3 seasons old bought brand new). SO i talked to dealership got a new bolt, had to tear this thing apart to get it back together. Made sure everything was aligned and running. Mid season everything came lose again. I tore it all down and re tightened everything down and it was fine.

Jump to this season - first time out tensioner broke again and i had to rebuild it all again, and everything seemed fine. 2nd time out and the dam thing literally exploded with parts all over the driveway. Plastic casing on drive shaft shredded, broke the protective guards, broke chain and I assume its because tensioner bolt broke again under use!

So I filed a claim with Kubota Insurance and dropped it off for repair. Now almost 2000.00 in repairs and the second time I take it out to remove 3-4 inches of soft snow on my 1/4 mile driveway I senses a vibration, shut it all down and the darn tensioner bolt is broken AGAIN!

There has to be something I and the dealership is missing! What would cause that to break again? I am assuming some ungodly torque or force is breaking it. See pictures attached.

Does anyone have ANY ideas? I am desperate. In the middle of snow season and we have gotten over 40 inches of snow in December.

FYI - Now dealership wants me to get machine and snowblower into the dealership. At My cost! I do not have a trailer big enough and would cost over $200.00 each way!

I am so freaking irritated. Been out of work since June. I purchased a grading pusher blade a week ago to get by (1800.00) but now they want the whole kit and kaboodle! I'm screwed!!

 

[ItBmine]

You say that is the chain tensioner? How is your chain? No seized links? Not getting ice caught between chain and sprocket? Sprocket wasn't seized? Chain was in alignment?

Man, that's odd.

 

[mholka]

You say that is the chain tensioner? How is your chain? No seized links? Not getting ice caught between chain and sprocket? Sprocket wasn't seized? Chain was in alignment?

Man, that's odd.

Brand new chain. Dealership rebuilt it and I picked it up Tuesday. No ice is getting in there. I spray chain lube in it after every use. And today was just 3-4 inches of light fluffy snow. So it should not have had much load on it.

 

[mholka]

Brand new chain. Dealership rebuilt it and I picked it up Tuesday. No ice is getting in there. I spray chain lube in it after every use. And today was just 3-4 inches of light fluffy snow. So it should not have had much load on it.

Here is a diagram. I have marked the location where the tension adjustment bolt location. This bold pulls the housing assembly to provide the proper chain tension.

That is the bolt that keeps breaking.

Added pics I have notations on!

 

[ItBmine]

That's odd. I have no ideas. I have a rear blower and it is a lot more simpler design.

Sorry I can't help....I haven't really looked at the front blowers in person.

 

[boz1989]

If I had to guess, I would say that a shaft is bent, and the chain was adjusted where the most slack was. When the sprocket moves the other way, it over tightens, and stresses the pulley to failure. To look for this, adjust the chain, then turn it by hand checking the tension several times during a full rotation. I bet you will find part of it tight, and others loose.

Sent from my LGMP260 using Tapatalk

 

[Dave_eng]

From memory, that basic blower can go on the front, driven by mid pto, or on 3 pt driven by rear pto.

The front pto, which runs at approx 2,000 rpm's, requires a reduction in speed so the fan is turning at 540 rpm.This is where the chain and sprockets come in.

In view of your history, I would be looking for a problem in front of the chain drive, i.e. the blower itself to see if anything is binding in it thus causing great strain on the chain speed reduction.

With the chain and sprockets off, the blower input shaft should turn easily with no binding points.

More photos of the overall setup of the blower on your tractor and the pto from tractor to blower.

An out of phase pto can cause extreme vibrations and thus the damage you are seeing. What is the history of the tractor, the blower and the time frame when they were mated together.

Dave

 

[mholka]

If I had to guess, I would say that a shaft is bent, and the chain was adjusted where the most slack was. When the sprocket moves the other way, it over tightens, and stresses the pulley to failure. To look for this, adjust the chain, then turn it by hand checking the tension several times during a full rotation. I bet you will find part of it tight, and others loose.

Sent from my LGMP260 using Tapatalk

Thank. Last time i had it apart turning the main sprocket everything moved easily and freely. I will try again. Thanks

 

[mholka]

From memory, that basic blower can go on the front, driven by mid pto, or on 3 pt driven by rear pto.

The front pto, which runs at approx 2,000 rpm's, requires a reduction in speed so the fan is turning at 540 rpm.This is where the chain and sprockets come in.

In view of your history, I would be looking for a problem in front of the chain drive, i.e. the blower itself to see if anything is binding in it thus causing great strain on the chain speed reduction.

With the chain and sprockets off, the blower input shaft should turn easily with no binding points.

More photos of the overall setup of the blower on your tractor and the pto from tractor to blower.

An out of phase pto can cause extreme vibrations and thus the damage you are seeing. What is the history of the tractor, the blower and the time frame when they were mated together.

Dave

Dave - The tractor and blower were new 3 years ago. And it was mated the first time by the dealership. I do remove it once spring hits.

On the main sprocket there is a collar of some sort that has a key to lock it in place and 2 set screws. That collar did come loose at some point and the set screws broke. This happened the first time the adjustment bolt broke last season. I had a heck of a time getting the set screws out and replacing them. I had to drill and tap it with the next size up. But the key was still in place and never came out. So I was confused as to how the set screws broke.

Maybe the timing or index (?) of the shaft with the sprocket is out of place?

with the chain off, everything moves freely and easily. No rubbing or binding at all.

I will try and get more photos tomorrow.

Thank you.

 

[kubotasam]

I just brought an older model of the same blower home yesterday so I am by no means an expert on this. I just went and looked at the adjustment bolt on mine. Please don't take my observations and comments wrong I am only trying to cover all the bases here.
Once the chain has been tensioned with that bolt, 4 other bolts- 2 on top and 2 on the bottom of the reduction box should take all of the strain of the blower operation.
Adjusting of chain should be.
A. Loosen 2 top & 2 bottom bolts
B. Adjust tension bolt to achieve correct chain tension
C. Tighten 2 top and 2 bottom bolts.

The bolt that keeps breaking on your blower should not have any pressure on it in operation. In fact you should be able to remove it and not affect operation after the chain has been tensioned. You don't say what happens to the 4 bolts that should keep the chain in the correct tension while operating. Are they shearing off also?

 

[Dave_eng]

Dave - The tractor and blower were new 3 years ago. And it was mated the first time by the dealership. I do remove it once spring hits.

On the main sprocket there is a collar of some sort that has a key to lock it in place and 2 set screws. That collar did come loose at some point and the set screws broke. This happened the first time the adjustment bolt broke last season. I had a heck of a time getting the set screws out and replacing them. I had to drill and tap it with the next size up. But the key was still in place and never came out. So I was confused as to how the set screws broke.

Maybe the timing or index (?) of the shaft with the sprocket is out of place?

with the chain off, everything moves freely and easily. No rubbing or binding at all.

I will try and get more photos tomorrow.

Thank you.

For a small part of your problem, stripped set or socket head screws.

Other members have had great success with this set of tools by IRWIN

http://www.irwin.com/tools/screw-bo...screw-extractors-532-series-plastic-case-sets

Here is what one member said last February:

Dave -

I ordered the IRWIN Hanson Multi Spline Est set right off Amazon. It was about $30 for a full set (more than I will probably ever need, but you never know). I got them yesterday and they work like CHAMPS on the stripped allen screws. As long as you follow the guidelines (drill bit size and extractor size, etc) this is one great piece of gear. Thanks for turning me to them! I will say this, there is nothing wrong with my allen wrenches - the drain plugs are crap. I would replace these hex plugs with a regular bolt if I could find one short enough to fit with the same threads - I am going to look. Even though mine were stripped when I first tried to remove them, the location of these drain plugs (close to the ground on the rear wheel is extremely susceptible to moisture and anything else that can and will freeze up a bolt. The world's greatest allen wrench is no match for a stuck plug made out of a weak (soft) metal. Poor choice of metal and design by the orange engineers. But these extractors worked great. I had already broke a couple of other cheaper extractors trying to get them out.

 

[gmbc]

I adjusted my chain on mine. There are two bolts on top to loosen up also the side shield need to come off to allow access to tighten the adjusting bolt. Tighten chain and check tension then tighten the top two bolts and should be good. reinstall the side cover of chain. Hope this works out.

 

[nbryan]

Loosen the bolts that jhold the tension just enough to allow the gear box to move. Adjust chain tension (with that screw that keeps breaking) so that the chain has the 1/16" play needed.

Check for chain play while slowly hand rotating the sprockets through several turns of the large sprocket.

There will likely be a noticeable lossening/tightening of the chain as it's rotated, as mine are it seems not perfectly round and the 1/16" slack can be taken up by that, and cause chain tightness at certain points in its rotation. Make sure there's ALWAYS that 1/16" play MINIMUM at all times while turning the sprockets.

Once you're satisfied it's not binding and the locking set bolts are re-tightened the adjustment bolt can be backed off slightly as it's not involved in holding the tension.

 

[GreensvilleJay]

kubotasam's post #10 sounds like the correct proceedure.
I was curious as every other blower I've seen ,has an idler sprocket that you adjust for tension. In yours you move the entire 'PTO sprocket assembly', called #1. so he's right , loosen 4 bolts, apply tension, TEST for several spins, then tighten the 4 bolts As others have said , everything should spin freely.

 

[DustyRusty]

If it is covered by the Kubota insurance, ask the dealership to replace the snowblower and give you the new one in exchange for the old one. I would have to believe that KTAC would rather spend the money once than keep putting money into a problem snowblower that can't be solved.

 

[nbryan]

TEST for several spins, then tighten the 4 bolts As others have said , everything should spin freely.

I would say thisplus check play for several more spins AFTER you tighten the 4 locking bolts.
From experience, the final tighten will slightly move the PTO sprocket assembly and the free play will no longer be correct. Mine seemed to over-tighten the chain.

Ruile of thumb: Always be tightening up the adjustment bolt with the sprocket moving to tighten the chain when you lock the 4 bolts. It may require pushing the assembly to loosen the chain a bit before re-tightening. Then snug the 4 bolts just enough that your adjuster bolt can still move it without binding.

Then there's almost no chain tension change when 4 bolts fully torqued.

Tighten the adjuster to just over 1/16" play minimum all around. Then tighten the 4 set bolts. then check chain play again.

 

[North Idaho Wolfman]

Dead Thread Revival!
Thanks GMBC
Check the dates people, This was from 2017!

 

[GreensvilleJay]

Maybe spin in the opposite direction a few times as well , just to see IF there's any 'weird stuff' going on ?
Perhaps when tighening the bolts, the 'assembly' gets cockeyed ?