Any guesses as to what caused this?

barelycompetent

81 XS650 Special
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So on Monday of this week I was riding my bike, and I had just pulled into my driveway and shut it off. Did a plug check and went to back it of my driveway and my rear wheel locked up. A sprocket bolt had backed out, caught the edge of the shock bolt, and dropped my chain adjuster down, bending that bolt to the point it snapped when I tried to take it off. I got a new sprocket bolt, torqued them all down to 27lbs, re staked all of the locking tabs, got a new to me chain adjuster and put everything back on the bike on Wednesday. Got everything lined up, got good tension on the chain, measured the adjusters to make sure they were both even, locked everything down, rolled the wheel, didnt hear any funny noises, checked the tension on various spots on the chain, and all seemed well. Last night Im cruising along on the highway about 70mph, and about 10 miles down the road I feel the entire back end shift and kick to the right on me. I pulled over and stopped the first chance I got and found that my plate bracket had been ripped clean off, the left side chain adjuster that I had just replaced, the bolt had broken off, my shock on the left side of the bike was bent, and my wheel had kicked over to the right and was rubbing against the brake stay. At this point, I have no idea what happened or caused it, and I am done risking my life working on it. It is going to a shop to have them go through the entire rear end. There was no side to side play on the swingarm and it was tight. Im stumped. The first two pics are of the damage from Mondays fiasco, the last three are from last night.
 

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Holy crap... The first think just look like it was caused by the sprocket bolts backing out and hitting something... but looks like you sorted that out right...

What do you mean plate bracket? Your license plate bracket? If so it sounds like it came loose and got sucked into the chain ? breaking your chain tensioner and bending your shock? Had to be a pretty stout plate bracket to bend your shock!

Sometimes the axle mounted plate brackets and work themselves loose... unless there is a tab or something that locks the location so it cant spin...
 
It was a homemade license plate bracket, it wasnt very stout at all, and I had it mounted where the rear passenger pegs used to be. Im guessing when the wheel kicked on me, the chain caught it and ripped it clean off. Im guessing wheel bearings or bent axle caused this, but thats all Im doing is guessing. Its shop time for this bike.
 
It was a homemade license plate bracket, it wasnt very stout at all, and I had it mounted where the rear passenger pegs used to be. Im guessing when the wheel kicked on me, the chain caught it and ripped it clean off. Im guessing wheel bearings or bent axle caused this, but thats all Im doing is guessing. Its shop time for this bike.

I'd say the real cause of this is how/where the licence plate bracket was mounted. It may have vibrated too close to the chain and got pulled into the chain. You need a re-design of the plate bracket mounting, making it more secure/stronger and larger clearance to the chain.

Its not caused by the wheel bearings or rear axle.

If you build a new bracket, post a pic before running the bike, so we can see how its mounted.

Edit: You should give consideration to using a chain guard, if you don't use one now. Chain guards are safety items.
 
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I suspect you might be right RG. I never thought about the plate bracket being the culprit. It is entirely possible that it vibrated to close to the chain and got pulled in by it, only to shoot out between the shock and the rear wheel, causing everything to shift. That could also explain why the chain adjuster bolt broke but left the lock nut there. All speculation really, but that is a very plausible theory. Im still going to take it to a shop and have them completely inspect the rear end just in case I screwed something up that isnt visible. I will post updates when I know more. So even if a wheel bearing went bad it wouldnt cause that kind of damage?
 
Sorry pic of my homemade plate bracket. It was mounted where the rear passenger pegs used to mount, right behind and slight above my exhaust muffler, but I dont have a pic of it mounted.
 

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Well at the shop their theory on the mystery is that the axle "ran out of thread". It appeared to be tight, and locked down when I torqued it, but there wasnt enough thread on the axle to completely lock it down, if that makes sense. So even though I had good torque and good readings the axle wasnt completely locked down. They are going to go through the back end to make sure there is no other damage, and then patch me up and get me back on the road. Eh it sounds plausible to me, who really knows.
 
Where there any threads showing out of the castle nut? If there were, that is horseshit. The first 3 threads of an fastener do 90+% of the clamping. They are throwing smoke at you because they truly do not know what caused it to happen.
 
one way to find out put a washer behind the axle nut then you know for sure you have enuff,also check your wheel bearings if a bearing locks up it will make the axle spin
also could have the lic bracket have came off and went through the chain and gear?
 
It is possible about the plate bracket, and it is possible with the wheel bearing too. All things that are going to be checked. I really think that a bearing went out, that and not having enough thread on the axle. My license plate bracket was just collateral damage. I will hopefully have more answers here shortly.
 
Well at the shop their theory on the mystery is that the axle "ran out of thread". It appeared to be tight, and locked down when I torqued it, but there wasnt enough thread on the axle to completely lock it down, if that makes sense. So even though I had good torque and good readings the axle wasnt completely locked down. They are going to go through the back end to make sure there is no other damage, and then patch me up and get me back on the road. Eh it sounds plausible to me, who really knows.

That's the biggest load of BS I've heard for a while. Scary to think that you're paying a motorcycle shop $100 an hour, to have "mechanics" with that lack of knowledge, do work on your bike.

If a cotter pin will go through the castleated nut, then the nut has all threads engaged on the axle. Any competent mechanic would know that.

There is no mystery.................your chain ate your bracket...........build a better/stronger bracket.
 
Ok so with that in mind, the cotter pin did go through the castle nut, and it was torqued down. Yet put a screwdriver through the hole on the right side of the axle and the axle can be moved, as it sits with the current damage. I dont know if the axle could be moved before because that is one thing I did not check, I torqued it and left it at that. So if a bearing went out, would that allow the axle to move, even with the castle nut torqued and a cotter pin thru it? There is no question about the plate bracket, the chain ate it, and I need to make a better and stronger one. I think there is more going on then just the chain ate it and caused all of that damage. Everything has to be checked to find out, so thats what is going on now.
 
With a screwdriver through the right end, the axle normally cannot be moved. Its not good that you can move the axle now. However, your rear axle assembly has been under some severe stresses, due to the various misadventures you have been having.

You need to read up on the rear axle assembly, using an exploded drawing. Perhaps the dreaded PO left out or added parts, such as incorrect spacers. If the rear axle is assembled wrong, then even with correct torque, there could be problems.

You better hope the shop mechanics actually search out the correct exploded view of the rear axle. Don't be surprised if they claim they had too replace the bearings................those guys are parts sellers...............their boss tells them to sell parts.
 
I have been going through the parts diagrams and I cant see anything that was left out. I put it all back the way it came off the bike. Agreed that the stresses it has been under are bad, and I have used this shop before with no issues. Really everyone is guessing until we actually get in there and start looking around. Even if my bearings are by some miracle still good, I wouldnt trust them after the load they have been put under, so replacing them is A OK with me. Im just thankful to be alive and that I didnt end up a stain on the highway.
 
Have a look at the axle adjuster holes, and if the axle has a stepped-down shoulder near the threaded end. Mix/matched parts could have the axle nut tightening the axle shoulder to the adjuster hole instead of the whole wheel width...
 
Thanks Twomany, that actually makes sense. Going off of memory I do believe I have that stepped down shoulder on the axle. Im not positive though. It would not surprise me in the least if I did, the PO of this bike seems to have done that with alot of things. Mis matched plugs in the bike when I bought it, mismatched tires front and back, would not surprise me if the axle wasnt the right one. I put it back the way I took it apart so if it was there it got put back on, if it wasnt I didnt know it and it didnt go on. Looking over the parts diagrams though I cant see anything that was missing, but I will have to check the axle as stated.
 
My thought is the axle adjuster he replaced. Did it have the proper thickness? If it didn't, then yes, the axle would run out of thread, and the whole axle assembly wouldn't be properly tight. At seventy miles and hour, the rear wheel would be walking around like crazy. Lucky that the only damage was to the bike, could've been a lot worse than a shock and license bracket.
 
The adjuster came off a parts bike, the year is unknown to me. I am lucky, very lucky. This bike tried to kill me twice in one week. Someone is sending me a message, but Im a stubborn bastard and I dont listen all that well lol. Its all things that need to be checked for sure.
 
That's the biggest load of BS I've heard for a while. Scary to think that you're paying a motorcycle shop $100 an hour, to have "mechanics" with that lack of knowledge, do work on your bike.

If a cotter pin will go through the castleated nut, then the nut has all threads engaged on the axle. Any competent mechanic would know that.

There is no mystery.................your chain ate your bracket...........build a better/stronger bracket.

not if the nut bottoms out on the treads first befor its tight ( don't see it too much on swing arm bikes but a lot on hardtailed one all the time)
 
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