YTA24V48 - Clutch Anti-Rotation Pin keeps snapping!

shas595

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Hello all

I have a YTA24V48 - Somehow the link that bolts to the frame to keep the clutch from spinning upon blade engagement keeps snapping. Mind you, its a 5/16" steel link (Item 197), pretty heavy duty.
It will run, then somehow it gets snapped, the clutch then is free to spin and rips the wires. This is the 4th pin I've replaced. Clutch works fine, its spinning freely when 12V Applied. I just cannot figure out how its getting broken.
You can see the top slot getting abused. What could possible cause the clutch to keep slamming into this pin and snap it.
I have notice the mower does rev up and down occasionally , but if the clutch is working then I don't see how that could affect it. Its driving me nuts!!

IMG_9667.jpg


pin.pngIMG_9668 (1).jpg
 

sgkent

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I don't know your mower, and you probably see the same thing I do in the photo, but something like the blade or another pulley seems to be hitting that clutch or whatever it is, and that may be shearing your link. The steel is worn and peeled back. Also you can see where the rivets look worn by something hitting it. Is the blade loose, or does it have enough freeplay in it to hit that part? Can it or the spindle rise up to where it comes closer to the part? Are any bolts missing from the transmission or blade pulley system that allow excess movement? Just suggestions until someone comes by who has seen this before. Try to figure out what is hitting it first and that may lead you to the cause. The yellow box is where the wear arc is, and the arrow points to how hard what ever is hitting it is gouging into the part. That whatever is probably also shearing the pin.
 

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bertsmobile1

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I think you are confusing effect damage with cause damage .
When the retaining pin sheared the clutch would have spun & that would have caused the damage in the photos
That clutch has been hammering the retaining pin far too much so something is causing the clutch to slam into the pin, back off & slam into the pin again.
Loose engine mounting bolts will do this
Failed belt tensioner will do this
Running a belt that is too tight & mowing thick tufted grasses ( or hitting a lot of tree roots or scaopling the ground a lot ) will do this
Running with a bent blade will do this
Failed spindle bearings will do this
A bent PTO shaft will do this
Running a deck that is too heavy for the clutch will do this .
A broken wire is the clutch coil that is consistantly making & breaking contact will do this
If that was in my workshop I would file that slot true then weld in a thrust plate so the pin only has about 0.030" of clearance .
Before that I would have run the engine for a few seconds to check the PTO shaft is not bent and of course given the engine a good shove to make sure it is tight in the frame .

This is going to be a difficult problem to diagnose because there are so many causes that could be the problem either by themselves or in addition to each other .
 

sgkent

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I think you are confusing effect damage with cause damage .
When the retaining pin sheared the clutch would have spun & that would have caused the damage in the photos
That clutch has been hammering the retaining pin far too much so something is causing the clutch to slam into the pin, back off & slam into the pin again.
Loose engine mounting bolts will do this
Failed belt tensioner will do this
Running a belt that is too tight & mowing thick tufted grasses ( or hitting a lot of tree roots or scaopling the ground a lot ) will do this
Running with a bent blade will do this
Failed spindle bearings will do this
A bent PTO shaft will do this
Running a deck that is too heavy for the clutch will do this .
A broken wire is the clutch coil that is consistantly making & breaking contact will do this
If that was in my workshop I would file that slot true then weld in a thrust plate so the pin only has about 0.030" of clearance .
Before that I would have run the engine for a few seconds to check the PTO shaft is not bent and of course given the engine a good shove to make sure it is tight in the frame .

This is going to be a difficult problem to diagnose because there are so many causes that could be the problem either by themselves or in addition to each other .
so when it spins what SPECIFIC part is it hitting that is gouging it so much?
 

shas595

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I think you are confusing effect damage with cause damage .
When the retaining pin sheared the clutch would have spun & that would have caused the damage in the photos
That clutch has been hammering the retaining pin far too much so something is causing the clutch to slam into the pin, back off & slam into the pin again.
Loose engine mounting bolts will do this
Failed belt tensioner will do this
Running a belt that is too tight & mowing thick tufted grasses ( or hitting a lot of tree roots or scaopling the ground a lot ) will do this
Running with a bent blade will do this
Failed spindle bearings will do this
A bent PTO shaft will do this
Running a deck that is too heavy for the clutch will do this .
A broken wire is the clutch coil that is consistantly making & breaking contact will do this
If that was in my workshop I would file that slot true then weld in a thrust plate so the pin only has about 0.030" of clearance .
Before that I would have run the engine for a few seconds to check the PTO shaft is not bent and of course given the engine a good shove to make sure it is tight in the frame .

This is going to be a difficult problem to diagnose because there are so many causes that could be the problem either by themselves or in addition to each other .
You are definitely on the right track. My first thought was, it would have to be hammering that pin repeatedly for the pin to break before the sheet metal on the clutch. The mower does surge, do you think that could be part of it? I *think* when the blades are engaged they are always engaged (not the clutch turning on and off repeatedly), but its hard to be certain; however the clutch itself looks OK, the contacting surfaces are not that scored, so I can't imagine that its turning on and off in the middle of mowing otherwise the contacting plated would be really worn in.

The last time I replaced it, I didn't even cut grass, had the deck all the way up and was just picking up what little leaves were left after fall cleanup, so no work really on the blades.
I have to say, this thing does shake pretty well; I mean its a mower, but it seems to shake more than it should.

My plan is to fix the clutch wiring, put it back in without the deck and run it and check on the pin after a while. If its damaged its outside the deck, if not then my issue is like you said, bad pulley or bend blades. I appreciate the input, Ill keep you all posted.
 

sgkent

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Trying to get my head around that arrangement.

The pictorial shows that part #13 and the pulley above it #12 go onto the crank. When you apply voltage the magnetism which then causes the clutch to grab and apply power. The coil and bracket is held from spinning by maybe the two pins, (#9 and your #197). https://www.jackssmallengines.com/j...de-mowers/yta24v48-96045005400-2015-07/engine

What part is causing the wear pattern? If it is the pulley #12 why does it have so much play like that to allow it and the clutch to rub? Bent crank or worn thrust? I dunno. But looking at #12 online it appears to have too much clearance between it and the clutch by design so that should not be the part that rubs. Is the belt coming off and grabbing everything as it wears and shears the pin? Is this model capable of having the belt hop on and off the pulley in between the pulley and clutch where it still drives the mower but causes it to shake? I dunno. Maybe StarTech or Bert will know the cause.

I would check to see if anything was loose, engine or the transmission mount bolts loose front or rear. I would also want to check the clutch bearing to be sure it wasn't gritty or worn out because if the bearing is grabbing that would put a lot of pressure on the link.

Most of all I would want to understand the wear pattern and what is causing it. I guess as Bert suggested it could be anything in its path when it spins, maybe a bolt or even the broken pin I guess etc.. When the bearing is working right there should not be that much pressure on it unless other stresses are involved like a loose mount etc.. The engineers would not have designed it as a high failure item, and if it was an engineering mistake Google would have brought up a lot of others with the same issue. Bert or StarTech will figure it out.
 

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ILENGINE

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Either that clutch is shaking really bad due to the crankshaft wobbling, or there is a bearing failing within the clutch causing it to hammer that hard. You should be able to hang onto the clutch with your fingers and keep it from rotating. There shouldn't be any pressure on the anti rotation pin
 

sgkent

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Either that clutch is shaking really bad due to the crankshaft wobbling, or there is a bearing failing within the clutch causing it to hammer that hard. You should be able to hang onto the clutch with your fingers and keep it from rotating. There shouldn't be any pressure on the anti rotation pin
could the belt hop with loose mounts in a way that would load and unload it over and over?
 

Hammermechanicman

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I would remove the deck and check all the bearings and inspect the belt for damage. A belt with a bad spot can cause the problem you are seeing.
 

bertsmobile1

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Surging should not be enough to shear the pin unless it is chronic enough to make the mower jump sideways
Surging can loosen the engine mounting bolts .
 
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