M500 Driven (Jack Shaft) Sheave Adjustment or New Part

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Howdy everyone, this is my first post here but I've found these forums a tremendous wealth of information over the years. Thanks everyone for going out of your way to share your wisdom!!!
I don't ever need to post here or elsewhere because I can find almost every answer I need by conducting incredibly thorough multi-hour searches. I prefer not to impose.
At any rate, I've got an old M500. I think it's an M500, the plate is present but so worn its unreadable and someone simply used a label printer and put a "500" below the Bobcat emblem on the side. It's got a new Honda engine with only 50 hours on it. The engine mount broke due to crappy welds a few months back. To get it aligned right for re-welding I had to pull the variable sheave. I didn't align the marks when I reassembled. I ran it for a few hours afterwards and the belt started shaking up and down really bad while running the machine and the driven (jack shaft/spring) sheave looked wobbly. I finally realized it might be the variable sheave alignment so I took it apart today to re-align....still not sure I figured that one out, read some posts on here about the alignment, I ended up just aligning the 6 little holes drilled on each side of the variable sheave assembly. Put it back together, belt is still shaking like crazy. Looked closer and discovered that the driven sheave is out of whack pretty bad, that is definitely causing the fast vertical belt wobble. By "out of whack" I mean that the STATIONARY side of the driven sheave wobbles by quite a bit. This moves the belt up and down as it rotates like crazy. I have no idea how to adjust this, but judging by the 600-series manual it should fit tight on a shaft and NOT wobble.

Is there a way to adjust this or something? Or is it not sitting on its shaft properly, which to me means its broken? It looks like the outside (towards the clutch/outside plate near the wheels) has been welded, so it should probably be replaced. Does the dealer have parts for this old beast? (Nearest one is 4 hours away, I live in the middle of nowhere).
Did me putting the variable sheave on out of alignment cause the driven sheave to derail like this? It was definitely not like this before!!!!

Thanks in advance, ~Josh in Southern Utah

 

[antfarmer2]

I would call the dealer and see if they can get it if they can pay for it with a card and have them ship it to you

 

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I would call the dealer and see if they can get it if they can pay for it with a card and have them ship it to you

Thanks Antfarmer, I'll give them a call on Monday when they're open.

Any good sources for used parts? I've had this thing over a year and only have 60 hours on it, used is perfectly adequate for my uses!

Thanks
~Josh

 

[6brnorma]

Thanks Antfarmer, I'll give them a call on Monday when they're open.

Any good sources for used parts? I've had this thing over a year and only have 60 hours on it, used is perfectly adequate for my uses!

Thanks
~Josh

Josh….there were two types of shaft/sheave assembles. One had a straight shaft, pressed on sheave with a lock nut, the other is a tapered shaft with a spanner type locking nut. I am just guessing that yours is the older straight shaft type. Obviously if it was welded it had prior problems…..bad timing because there were two of them available on e-bay just a couple of days ago (about $150.00 for shaft and entire assembly) but I don't see them now. They are pricey from the dealer…..let me look around and I'll see if I have one laying around or watch e-bay…..one will show up again sooner or later.

 

[mark18mwm]

I'm not sure about your problem with it having been welded. As for the alignment, my 600 has a arrow cast in the sheave that points to the outside of the sheave. My inside sheaves has a alignment mark on the very outside rim of the sheave, it's very small. It looks like a some one would have marked it with a chisel, just 1 small grove that is very hard to see and I only found it dragging my thumb nail around the sheave. I have been told I have a mismatched set of sheaves, the should be marked the same on the inside and out side, meaning both have arrows or both have the chisel type marks. mine may well be mismatches but they have been like this since I got it a couple years ago and they seem to work fine. Once you find these marks, align them up with one another and you should be all set as far as alignment. Good luck.

 

[6brnorma]

I'm not sure about your problem with it having been welded. As for the alignment, my 600 has a arrow cast in the sheave that points to the outside of the sheave. My inside sheaves has a alignment mark on the very outside rim of the sheave, it's very small. It looks like a some one would have marked it with a chisel, just 1 small grove that is very hard to see and I only found it dragging my thumb nail around the sheave. I have been told I have a mismatched set of sheaves, the should be marked the same on the inside and out side, meaning both have arrows or both have the chisel type marks. mine may well be mismatches but they have been like this since I got it a couple years ago and they seem to work fine. Once you find these marks, align them up with one another and you should be all set as far as alignment. Good luck.

Mark…..if I understood him correctly, he is talking about the 'jackshaft' sheave. They are not a balanced pair, have no alignment marks and can be matched with other than the original half.

 

[mark18mwm]

Mark…..if I understood him correctly, he is talking about the 'jackshaft' sheave. They are not a balanced pair, have no alignment marks and can be matched with other than the original half.

Yup, your right. Sorry I misunderstood. I had to re-read, and you are correct. I wish I could say that was the first time I was wrong (even just today lol).

 

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Yup, your right. Sorry I misunderstood. I had to re-read, and you are correct. I wish I could say that was the first time I was wrong (even just today lol).

Thanks for the tips on the variable sheave adjustment. I'll look for that little nick in the other half and make sure to get it right this third time around!!!

I'll see what the dealer says for cost on a new part, it's definitely good to know a general ballpark on a used part for comparison so thanks for giving me that info.

I hate to have this thing down because it just keeps snowing and snowing and it's killing me not being able to plow!!! Do you think I could potentially ruin anything if I ran it for a few more hours while waiting for a replacement part? The belt or maybe the bearings that hold the jack shaft?

Thanks again for all your advice,
~Josh

 

[6brnorma]

Thanks for the tips on the variable sheave adjustment. I'll look for that little nick in the other half and make sure to get it right this third time around!!!

I'll see what the dealer says for cost on a new part, it's definitely good to know a general ballpark on a used part for comparison so thanks for giving me that info.

I hate to have this thing down because it just keeps snowing and snowing and it's killing me not being able to plow!!! Do you think I could potentially ruin anything if I ran it for a few more hours while waiting for a replacement part? The belt or maybe the bearings that hold the jack shaft?

Thanks again for all your advice,
~Josh

You are virtually assured of further damage and potential personal injury. Last year one of my men didn't properly service his machine and didn't pay attention to the wear. The moving half of the same sheave you are having troubles with, wore through the bushings, into the steel portion of the sheave causing the exact same 'wobble' you are describing. At full speed the shaft broke completely off hitting the seat. It took me several days and several thousand dollars to repair the machine……..replaced parts included …..both shafts, entire sheave assembly, belt, broken chains on both sides, broken/damaged gears, clutches, bearings, hydro lines……………..and my employee's underwear. I highly recommend repair first. The last dealer price I had for the entire assembly was $610.00……that was several years ago. Good luck.

 

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You are virtually assured of further damage and potential personal injury. Last year one of my men didn't properly service his machine and didn't pay attention to the wear. The moving half of the same sheave you are having troubles with, wore through the bushings, into the steel portion of the sheave causing the exact same 'wobble' you are describing. At full speed the shaft broke completely off hitting the seat. It took me several days and several thousand dollars to repair the machine……..replaced parts included …..both shafts, entire sheave assembly, belt, broken chains on both sides, broken/damaged gears, clutches, bearings, hydro lines……………..and my employee's underwear. I highly recommend repair first. The last dealer price I had for the entire assembly was $610.00……that was several years ago. Good luck.

Haha, damn, I figured I'd get some kind of horror story but I didn't think it would involve the same exact part!!!! Thanks for the warning, it is duly noted and the Bobcat will remain stationary until a replacement part can be found.

I just called the dealer, apparently the straight shaft version has been discontinued and is no longer available. They offer the tapered shaft driven sheave as a replacement for $700 plus another $220 for the tapered shaft itself and you also need a slough of additional parts to make the conversion. Doesn't sound like a great option, I guess I'll have to wait around for some used parts to pop up!!!

Is there an easy way to tell between the tapered vs. straight shafts without tearing the whole thing apart? I don't have a good place to leave the thing splayed open while I wait for a replacement part but if it took me an hour to tear some things apart and reassemble just to be sure which shaft I have it would be no problem.

Thanks again,
~Josh

 

[antfarmer2]

Haha, damn, I figured I'd get some kind of horror story but I didn't think it would involve the same exact part!!!! Thanks for the warning, it is duly noted and the Bobcat will remain stationary until a replacement part can be found.

I just called the dealer, apparently the straight shaft version has been discontinued and is no longer available. They offer the tapered shaft driven sheave as a replacement for $700 plus another $220 for the tapered shaft itself and you also need a slough of additional parts to make the conversion. Doesn't sound like a great option, I guess I'll have to wait around for some used parts to pop up!!!

Is there an easy way to tell between the tapered vs. straight shafts without tearing the whole thing apart? I don't have a good place to leave the thing splayed open while I wait for a replacement part but if it took me an hour to tear some things apart and reassemble just to be sure which shaft I have it would be no problem.

Thanks again,
~Josh

The dealer should be able to tell you what you should have by the s number

 

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The dealer should be able to tell you what you should have by the s number

Unfortunately my serial number is worn off the plate and totally unreadable! The plate is there, but it's just a piece of bare metal riveted to the frame now.

The guy over at Dakota Skidsteers told me that the straight shaft only came as a single unit (doesn't separate in two) and since mine separates in the middle it must be tapered. I find this slightly odd as the manual I have for 600s describes both tapered and straight and shows them both separating in the middle. I think I just need to tear it all down, then I'll know for sure.

Hopefully its tapered as I've found a used replacement for $350 or so from Dakota Skidsteers. If its straight then I guess I'll have to replace everything necessary to make it tapered because the straights are really hard to find.

~Josh

 

[antfarmer2]

Unfortunately my serial number is worn off the plate and totally unreadable! The plate is there, but it's just a piece of bare metal riveted to the frame now.

The guy over at Dakota Skidsteers told me that the straight shaft only came as a single unit (doesn't separate in two) and since mine separates in the middle it must be tapered. I find this slightly odd as the manual I have for 600s describes both tapered and straight and shows them both separating in the middle. I think I just need to tear it all down, then I'll know for sure.

Hopefully its tapered as I've found a used replacement for $350 or so from Dakota Skidsteers. If its straight then I guess I'll have to replace everything necessary to make it tapered because the straights are really hard to find.

~Josh

Wipe the plate good with a rag then put a piece of thin paper maybe rolling lol and rub with light charcoal might surprize you

 

[6brnorma]

Wipe the plate good with a rag then put a piece of thin paper maybe rolling lol and rub with light charcoal might surprize you

Josh…..it is very easy to tell the difference between the two shafts. Look between the sheave and the side wall…..maybe a one inch space….. you can see the shaft and the back side of the sheave, if the sheave has a collar with a 'set' screw going into the shaft it is a straight shaft. The 'set' screw came original with a square head. The taper shaft will have nothing on that back side. Both the taper and straight shafts have the exact same "block" in the middle where you separate the two shaft halves. I don't believe the 'parts' man is correct in saying that you need additional parts to convert to the taper shaft…….I do it all the time……both shafts mic out the same, length is the same…only difference is how the 'stationary' half of the sheave mounts to the shaft.

 

[6brnorma]

Josh…..it is very easy to tell the difference between the two shafts. Look between the sheave and the side wall…..maybe a one inch space….. you can see the shaft and the back side of the sheave, if the sheave has a collar with a 'set' screw going into the shaft it is a straight shaft. The 'set' screw came original with a square head. The taper shaft will have nothing on that back side. Both the taper and straight shafts have the exact same "block" in the middle where you separate the two shaft halves. I don't believe the 'parts' man is correct in saying that you need additional parts to convert to the taper shaft…….I do it all the time……both shafts mic out the same, length is the same…only difference is how the 'stationary' half of the sheave mounts to the shaft.

Also…….the straight shaft was a poor design (exactly what you are experiencing)…….that's why they went to the taper. I always toss those and go to the newer design. Your profile doesn't say where you are located.

 

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Also…….the straight shaft was a poor design (exactly what you are experiencing)…….that's why they went to the taper. I always toss those and go to the newer design. Your profile doesn't say where you are located.

I'm in Southern Utah.

It's hard to tell because someone welded all the hell over that side of the sheave. There was a bolt sticking out that I attempting to tighten and it was stripped and came right out. That makes me think it's the straight shaft then.

The parts guy at the dealer said there was a bunch of parts required to convert between the two. If it's just a matter of the sheave and the shaft and everything else is identical then I'll be fine because the guy is going to give me both the sheave and the shaft. I guess I'll just get it over here and see how it goes!!!!

~Josh

 

[mark18mwm]

I'm in Southern Utah.

It's hard to tell because someone welded all the hell over that side of the sheave. There was a bolt sticking out that I attempting to tighten and it was stripped and came right out. That makes me think it's the straight shaft then.

The parts guy at the dealer said there was a bunch of parts required to convert between the two. If it's just a matter of the sheave and the shaft and everything else is identical then I'll be fine because the guy is going to give me both the sheave and the shaft. I guess I'll just get it over here and see how it goes!!!!

~Josh

Josh, I found this on eBay. It's the tapered shaft that holds the sheave.http://www.ebay.com/itm/BOBCAT-610-SKIDLOADER-VARIABLE-SPEED-JACKSHAFT-DRIVEN-SHEAVE-/121231559172 Here is the other side of that shaft, but I'm sure the one on the right side that you already have would still work http://www.ebay.com/itm/BOBCAT-610-JACKSHAFT-W-ALT-PULLEY-/131066472651 I think that is a good price on the tapered shaft, I could not find one last spring and needed one asap and had mine repaired localy but I would have bought one at this ones price. Hope this helps, even though you would still need to find a tapered sheave.

 

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Josh, I found this on eBay. It's the tapered shaft that holds the sheave.http://www.ebay.com/itm/BOBCAT-610-SKIDLOADER-VARIABLE-SPEED-JACKSHAFT-DRIVEN-SHEAVE-/121231559172 Here is the other side of that shaft, but I'm sure the one on the right side that you already have would still work http://www.ebay.com/itm/BOBCAT-610-JACKSHAFT-W-ALT-PULLEY-/131066472651 I think that is a good price on the tapered shaft, I could not find one last spring and needed one asap and had mine repaired localy but I would have bought one at this ones price. Hope this helps, even though you would still need to find a tapered sheave.

Well, I'm pretty well dug into the thing to remove the jack shaft and driven sheave. Very fun and easy to work on, plenty of room....far better than a car!!!! The whole shaft half with the pulley appears bent which is a little odd; I went ahead an ordered a new bearing for it as well.

One odd thing: The jackshaft half doesn't have enough clearance to drive it out of the bearing. It runs into the other jackshaft half. Even with the one half bent there isn't enough play to get the shafts to clear each other. All I can think to do is pull the bearing (which I'm going to replace anyway so no big deal) but the manual clearly indicates it should have no problems coming out and I'm not sure pulling the bearing will help much. Any ideas?

Thanks,
~Josh

 

[6brnorma]

Well, I'm pretty well dug into the thing to remove the jack shaft and driven sheave. Very fun and easy to work on, plenty of room....far better than a car!!!! The whole shaft half with the pulley appears bent which is a little odd; I went ahead an ordered a new bearing for it as well.

One odd thing: The jackshaft half doesn't have enough clearance to drive it out of the bearing. It runs into the other jackshaft half. Even with the one half bent there isn't enough play to get the shafts to clear each other. All I can think to do is pull the bearing (which I'm going to replace anyway so no big deal) but the manual clearly indicates it should have no problems coming out and I'm not sure pulling the bearing will help much. Any ideas?

Thanks,
~Josh

After you have removed the primary drive chain…….both shafts will (should) pivot about 60 degrees in any direction. If they will not, your bearings are frozen into the housing……you probably will need to replace both bearings. I have seen many of these bearings replaced with the incorrect bearing housing……..when tightened it presses the bearing against the sidewall and does not allow free movement of the bearing itself. Let me know if you need a part #…….much cheaper from a bearing and chain house than dealer.