Clutch and Throwout Bearing

[North Idaho Wolfman]

Use some brake parts cleaner or carb cleaner, a wire brush and clean everything up, you should be able to see the difference in the 2 metals, one will be steel (silver) and the other will be bronze (brass).
Don't bother using a blade to cut it, just use a small chisel as the bronze is very brittle and will just chip out.

 

[2458n]

When you have your new bearing in hand-reread the part about using a wooden dowel rod and grease. This is the easiest way to remove the bearing and it will come out in one piece. You are doing fine and the stuff needs replaced anyways. Determine if your splitting time is worth not replacing the clutch face..

 

[pbaumeister]

Ok. I ordered the pilot bearing and it came in. I was going to size it up with the hole where it goes and it fell in. The pilot bearing is about 2 mm too small than the fly wheel. and smaller than the bearing seal. I checked the pilot bearing to see if it goes over the clutch rod/propeller shaft and it fits perfectly. So it looks like the shaft wore down to nothing and then it bore the hole in the fly wheel and bearing seal to be larger.

Here is a picture of the fly wheel with the pilot next to it to see the difference in size.

Here is the picture of the flywheel without the pilot next to it.

Here is a picture of the bearing seal in the crankshaft.

My questions are these:

1. Is that normal for the fly wheel to be much larger than the pilot bearing? If so, do I need to purchase a new fly wheel?

2. Do I need to purchase a new bearing seal (the one in the crankshaft)?

 

[North Idaho Wolfman]

The bearing doesn't fit in the flywheel, it fits in the end of the crank, behind the dust seal.

 

[pbaumeister]

Thanks Wolfman!

I removed the seal from the crank. I looked at the rest and it seemed that there is no pilot bushing in the crank. Is it possible it wore out? I dropped the new pilot bushing in there and it is smaller than the hole.

Crank with new pilot

Crank without the new pilot

 

[North Idaho Wolfman]

Uggg not good, yes it sounds like it was out long enough to have worn the crank hole out.

Just to make sure what was the P/N of the pilot bushing you ordered?

 

[pbaumeister]

I purchased it on eBay. The item number is 66621-14120
My tractor is a 1980 Kubota B6100DT.

The above item is for a Kubota B6100DP, B6100EP, B6100HSTD, B6100HSTE, and B6200D.

I have the original parts catalog, but the part number there is a little different. It is 66621-14121.

 

[North Idaho Wolfman]

Ok now for the really bad news, there is only one way to fix it right, you would have to completely disassemble the motor and take the crank to a machine shop to have that bearing surface milled and sleeved to fit the bearing.

Now for the shade tree repair version, get epoxy putty, you need to have the transmission ready to install very quickly.
Leave the flywheel and clutch and shaft seal off, clean hole in end of crank with some emery cloth and brake parts cleaner (very clean), have transmission in line to assemble fast, coat end of transmission shaft with a light layer of grease, , kneed putty till mixed completely, wrap putty around bearing, install bearing in hole, filling in the space around bearing with putty, quickly clean out any excess from inside hole, mate transmission up to motor (this will help align bearing), will only need to install a couple bolts to hold it in place, let sit for 24hours, remove transmission install all components like flywheel (carful installing it, if you didn't mark it's orientation to the crank) , it does actually only line up one way, all others will have bolt holes slightly off, it's hard to tell, but if you cant hand start and turn every bolt it's probably not lined up.

 

[pbaumeister]

I just wanted to follow up in case someone has the same problem. I found out the pilot bushing was completely worn to nothing and the shaft bore a larger hole in the crankshaft where the pilot bushing goes. The only fix was to use the new pilot bushing as an example for creating a thicker pilot bushing. I purchased a brass fitting with the same inner diameter as the new pilot bushing. Then I measured the diameter of the hole where the bushing should go. Then I had a friend turn the brass fitting until it was that measurement and a little larger. It worked perfect. I hammered it in there with a piece of wood and it fit perfect. No noise now. Runs like a charm.

 

[BadDog]

I'm glad you are happy with the fix, but I wouldn't be comfortable recommending it. I suppose it's likely good enough and will last a while, but it's highly unlikely that the wear is concentric to the rotation axis. Which means that with a concentric bushing in there, the shaft won't be spinning on axis. That then yields fatigue on the shaft and stress on the front support bearing (and beyond). Obviously we're not talking about a 7k+ rpm motor here, but as seen in the multitude of odd wear and fatigue failures found on many of these tractors (sad how well I know), it does add up.

 

[pbaumeister]

You're right about it not being concentric. It wore it out between 2-3mm. So my pilot bushing is probably not completely centered. Do you think that the shaft will wear it out to be concentric?

 

[D2Cat]

pbaumeister, your solution wasn't the ideal, but I would have done that or something very similar before I'd break down the engine to get the crank worked on.

If there was some way to set up a jig on the flywheel to cut the oversized bushing true to center would be nice, but not owning a machine shop, you have to do with what you've got!!

You may be surprised and get several years of use out of it.

 

[BadDog]

I don't think it will wear out to be concentric any more than the original hole wore to be concentric, but I do think it's going to wear faster on the shallow side due to always bearing the load there. The pilot bushing is not really meant to handle load at all. It's there to keep everything on axis, mainly when the clutch is disengaged or changing state (on/off).

But as stated, depending on how you use it, you may get years of wear out of it. Particularly if you got lucky and it did wear more concentric than not. I'm not that familiar with tractors in general, but that repair wouldn't last long at all on a daily driver or performance toy.

If it were me, just spit-balling here, but I would probably have tried to figure out a rig like they use to bore worn pivot pins in loaders and other such equipment. Basically a bridge across the back of the block, as rigid as possible, and then setup a "feed" to hold a boring bit. Maybe a lathe compound repurposed, or anything where you have a relatively rigid mount and ability to control feed. On those implement line boring tools I've seen the bit advanced with just a block welded behind and a bolt threaded through with a trough and clamp to guide/hold the bit. Anyway, once you have the boring bit mounted in the worn bore, crank the tractor. Very dangerous near strong spinning things, so be very careful, and feed the boring bar to make the hole concentric to the turning crank. Then fit a custom bushing/bearing to that concentric hole and you have a repair that should last a good long while.

 

[ShaunRH]

I would not do on device line boring without some experience on less expensive things first. Any decent machine shop can do this function with accuracy.

 

[BadDog]

That's a very reasonable position, certainly wouldn't want to scrap it. I have my own machine shop, so while I feel I could make it work, it should be said that you try at your own risk, your mileage may vary, and so on.

The problem with taking it to a machine shop (at home or elsewhere), is that you will need to tear the motor down and remove the crank. If I cared to do so, or if there were other motivators like a general freshening or fixing leaks, then I would much prefer to do this on my lathe (7.5 hp 17x60 at nearly 5k lbs, certainly up to the task). But if the motor were otherwise good and the damaged bore were my only concern, I would likely try to find another way.