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Homelite trimmer hot shaft bushing


mdevour's Avatar
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09-21-13, 03:52 PM   #1  
Homelite trimmer hot shaft bushing

Hi all,

I was given a Homelite curved shaft 26cc trimmer, model UT21506, s/n ATK2040240 from mid 2007. After getting it to run, I discovered the shaft bushing is getting hot -- hot enough to melt the plastic guard! I'm guessing the bushing is contaminated and probably shot. That said, there's only about 40 thousandths or so of end play and no wobble or side-play that I can detect.

I don't see a way to disassemble the bottom end, as the bushing assembly seems to be swaged into the shaft tube. I've removed and re-lubed the flex shaft. I've tried running the shaft end in solvent in hopes of flushing any debris out of the bushing, and put some oil down the top end of the tube. While that slowed the rate of heating, it still gets too hot to touch after a couple of minutes running.

A new shaft assembly is about $45 plus a hefty shipping fee, so it's past borderline whether it's worth fixing. I've seen suggestions here to see if the local repair shop will sell me a used one...

So, have I missed anything? Can I disassemble the bearing for proper cleaning? Do you think there is any hope of resurrecting it? Any other thoughts or suggestions before I "retire" this unit?

Thanks!

Mike

 
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09-21-13, 04:16 PM   #2  
In your shaft tube about where the lower handle is, I would slide the handle out the way temporarily and drill an 1/8 " hole in the shaft tube. Then put a couple ounces of heavy lube like chain lube down the tube. Run it for a couple minutes, then repeat, move the handle back over the hole you drilled and see where you're at with it. That will keep the drive lubed too.

 
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09-21-13, 10:30 PM   #3  
If you have .040" play, it sounds like it's shot and lubing it may get you some more use out of it, but not for long. Check ebay and your local small engine shops for a used one.


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09-23-13, 12:20 PM   #4  
Thanks for answering, folks.

Again, this is about my Homelite curved shaft 26cc trimmer, model UT21506, s/n ATK2040240 from mid 2007, on which the bearing at the end of the shaft is getting hot enough to melt the plastic guard.

marbobj,

Okay, rather than drill a hole, I pulled the plastic guide out of the shaft tube and poured the oil in the end. Put it back together and ran it, the bushing is still getting too hot. An occasional drop of grease/oil made it past the bearing during the run, so I know the lube is getting to where it's supposed to.

I'm guessing that the bushing got contaminated and has some dust or grit embedded in the working surfaces, and nothing will fix it. Does that sort of thing happen? Or should it be possible to clean it out? Is there anything else that might be causing it to get hot? Anybody?

Cheese,

You wrote: "If you have .040" play, it sounds like it's shot..."

I'd like to know why you suspect this? The bearing shows no play at all except a bit more than 1/32" in and out. No rattle or wobble at all that I can detect by hand. I checked a display model at Home Depot and it had a lot more end-play than this one and felt just as solid otherwise. If it didn't get hot I'd never suspect it of being worn out?

I'll probably head out tomorrow to a local repair shop and see if they have a used one they're willing to sell me.

Thanks,

Mike

 
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09-23-13, 02:42 PM   #5  
It may very well be the bushing was dry, then heated which could have layered metal from either of the mating surfaces and cut the tolerance at the bushing, resulting in a heat up. Since you're getting lube past the bearing and it's still heating I'm not sure what else you could do for it.

 
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09-23-13, 08:57 PM   #6  
Sorry, I was seeing end play but thinking side play. End play shouldn't be a problem so much.


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09-24-13, 10:47 AM   #7  
marbobj wrote:
It may very well be the bushing was dry, then heated which could have layered metal from either of the mating surfaces and cut the tolerance at the bushing, resulting in a heat up.
It's galled up, then. That's a definite possibility.

cheese wrote:
I was seeing end play but thinking side play. End play shouldn't be a problem...
Ah, that feels better. I was beginning to worry there was something really subtle going on.

Well, the local repair shop didn't have a used one, but he doesn't charge shipping on parts. So I ordered the shaft assembly for about $40. That still borders on the silly since the same trimmer new would be only $70, but at least I'll have the satisfaction of having fixed the thing and learned a bit in the process.

Thanks,

Mike

 
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10-05-13, 10:00 AM   #8  
Picking up on this thread, yesterday I got the new shaft for my 2007 vintage 26cc curved shaft Homelite trimmer from the repair shop. I just installed it and started 'er up.

After less than a minute the bushing on the new shaft is getting warm enough to notice, and I'm leery of letting it get hot enough to risk damaging it before I ask if there's something I'm doing wrong or if this is normal for a brand new bushing?

Are they properly lubed from the factory, or should I be putting some oil down the shaft before I even start?

Any thoughts?

Thank you,

Mike

 
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10-05-13, 07:04 PM   #9  
Any type of bushing or bearing that involves friction and movement (and that takes in about 75% of them) you will have heat generated. The build up will hit a threshold where it dissipates into surrounding metal/air/other material and maintains an operating temperature. That temp may or may not be significant to it working properly.

So in your case, the heat build up is likely normal and just as likely you don't have to lube the bushing. The flex shaft is normally the part that needs lubes.

 
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10-05-13, 08:12 PM   #10  
Posted By: marbobj Any type of bushing or bearing that involves friction and movement (and that takes in about 75% of them) you will have heat generated. The build up will hit a threshold where it dissipates into surrounding metal/air/other material and maintains an operating temperature. That temp may or may not be significant to it working properly.
Thanks. That's what I'd expect and hope for. Naturally I'm a bit squirrelly about it. As far as I've let it go, it's feeling like exactly the same rate of heat build-up as the one I'm replacing. That one continued to get hotter, to the point it would scald your hand. It even melted the plastic guard the first time I ran the thing after getting the motor to start.

One other data point is my brother's trimmer of the same model which is several years older than this one and still original parts. I checked it early on and its bushing runs perfectly cool. You can't feel warmth from it at all, even after an hour of heavy use.

You can tell how they've cheapened the design of the whole trimmer between his earlier year and this one. I'm concerned that they've cheaped-out on the bushing specs as well, and the things are doomed to early failure straight from the factory. I hope not, and I'd expect word to have gotten around if this was a problem well before now. Have you seen anybody else do this lately?

So in your case, the heat build up is likely normal and just as likely you don't have to lube the bushing. The flex shaft is normally the part that needs lubes.
I can see that eventually, though even the flex on the one I replaced was no trouble at all. The plastic guide was in perfect condition when I took it apart, and there was never any sign of heat anywhere except the bushing. The new one has a nice coating of grease on the cable.

Seeing as I have no idea of the history of this trimmer, the nightmare scenario is that the part I just replaced was already a replacement and they're all screwed up in the same way... only the news hasn't spread yet.

I'll consult with the guy at the repair shop, too, on Monday. See if he has any advice.

At some point I'll just have to let it run and find out We'll know then.

Thank you,

Mike

 
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10-07-13, 09:58 AM   #11  
Well, I've gone a step further testing the new shaft on this 26cc curved shaft Homelite trimmer. The bushing at the trimmer head gets hot, too hot to touch for very long, but so far not hot enough to melt the plastic of the guard as happened with the one I replaced.

Does anybody know if these always run as hot?

If it's supposed to run scalding hot but not melting hot, then I wonder if my effort to lubricate the old shaft might have been more successful than I gave it credit for. How would I tell, except by reinstalling the guard and waiting for it to melt, which I never did? I could swap it back in and test it, but I'm not sure I want to know.

Well, much to my embarrassment, I'm sitting here with about $80 in parts into a used trimmer that you can buy new for about $70 at Home Depot. Ah, but the education was cheap!

So I tell myself.

Mike

 
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10-07-13, 04:57 PM   #12  
I've never noticed them getting "scalding hot" without there being a problem. Are you using the original head for it?


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10-07-13, 09:22 PM   #13  
Posted By: cheese I've never noticed them getting "scalding hot" without there being a problem. Are you using the original head for it?
The head that came with it, but I have no clue if it is original. I'll check some numbers on the parts web site in a moment, but I've run the old shaft both with and entirely without the head and there wasn't any change in the heating that I could detect by hand. The new one I've only run with the old spool and knob, and a new head housing that exactly matches the old one that was missing one eyelet.

The homelite.com site links to http://hcpi.arinet.com/scripts/EmpartISAPI.dll?MF. Entering the model number, 21506, and accessing the UT21506 "Figure A" diagram, yields the part number for the head housing they call out: 308746001.

The shop ordered that part for me, but when it came in it didn't match the one I brought with me to compare. The counter guy recognized the part and pulled one out of stock that was the same. It has a part number 099068001005, which comes up on the site as one for a straight shaft Trimmer Attachment UT-15522-E, for whatever that's worth.

So it's probably not the head it shipped with. What are you thinking might be going on?

I can try running the new shaft with no head?

Thank you,

Mike

 
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10-07-13, 09:39 PM   #14  
Well, a head that is heavy or out of balance could cause the bushing area to heat up more than usual.


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10-08-13, 09:29 AM   #15  
Posted By: cheese Well, a head that is heavy or out of balance could cause the bushing area to heat up more than usual.
I just ran the thing for at least 5 minutes with the head removed, just the bare shaft. The bushing area still gets hot enough you cannot touch it for more than a 3-4 seconds before you have to let go. Is that a fair test, or is running it with too light a load going to cause the bearing to heat, too?

Curiouser and curiouser!

Could there be anything wrong with the power head that would cause bearing stress?

Grasping at straws, here.

Thanks,

Mike

 
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10-08-13, 10:02 AM   #16  
That eliminates the head. I guess it's down to either lack of lubrication or design flaw.


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10-08-13, 12:39 PM   #17  
Posted By: cheese That eliminates the head. I guess it's down to either lack of lubrication or design flaw.
I just did another couple of tests. The second was to put a couple of ounces of chain oil down there. It's still getting hot. Pretty much eliminates the lack of lubrication angle, I imagine.

The first was the more interesting... My first investment in the thing was to replace part of the recoil starter that broke. I wanted to make sure I didn't make some mistake assembling that part that would put any kind of extra thrust load on the bushing. I took out the screw that locks the shaft into the power unit housing and slid the tube out a bit more than 1/16" or so, then snugged down the clamping screw. I wouldn't run it this way long term, but it let me see if it would make any difference.

Before, the shaft was lightly sprung such that if you pushed it up into the bushing, it would immediately push back out to the limit of the end-play. With it extended in the clamp, it now moved in and out of the bushing freely. So I can be pretty sure there was no thrust load from the way the machine was assembled.

Unfortunately, it still gets scalding hot.

I'm about out of ideas. You?

So I can call it done and run it like it is until the guard melts or something else breaks. Or I call it a loss, and try to get the shop to return the shaft as defective, or otherwise dumpsterize my whole investment.

The only other option I can think of is to throw even more money at it and upgrade to a straight shaft. That would depend on the shop refunding at least most of the curved shaft, and giving me a similarly good price on the new parts. Depending on price, I'd end up with the better machine for only a bit more than it would have cost for a new one of the same quality. Not pretty, but at least I'd have a working trimmer and be done with all this.

Peace,

Mike

 
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10-08-13, 03:34 PM   #18  
Doesn't make sense to me. I have felt some of them get pretty hot, but not what I call "scalding". I wonder, since "hot" is a relative term, if it is just at normal temps and it feels hotter to you than you think it should be? I'd say run it.


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