Stripped bolt for pumpkin acorn nut

BuellOnYamaha

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May 10, 2020
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Hi: In removing the rear drive unit to replace a leaking oil seal, I had to wrench hard to remove one of the acorn nuts. so hard that the nut was almost too hot to touch from all the friction when it finally came off. I see the first thread or two on the bolt is stripped -- guessing a previous owner cross threaded it when putting it on and just muscled past it on a second attempt. I'm ready to reinstall and feeling a little nersvous about this. Thought of trying to hack saw off the last 1/18 inch of that bolt to amputate the ruined threads, but that feels kind of imprecise for an acorn nut with a precise depth. I'm not kean on opening up the pumpkin assembly to try and replace the bolt -- not sure what will shake loose in the process and i'm not even sure how to order that part (but that's probably a solveable problem). Should i just pull up my big boy pants and wrench it on, or does anyone have a hack for dealing with stripped threads?
 

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gv550

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That's not a bolt, it's a stud. No need to disassemble the final drive to replace it, just weld a nut onto it and turn it out of the final drive housing. It is probably loctited in there so apply heat to the aluminum housing before turning the stud out. Replace the nut as well, or it will ruin the threads on your new stud.
 

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It doesn't look totally stripped in the photo. Maybe run a die down it and see how well it cleans up, and add a new nut. If you want to replace the stud, (do what they have ^^^^^ suggested) or if you dont have a welder you can probably use 2-3 nuts and jam them together and get the stud out. I believe these have "thread lock" on them. Order a stud and new nut.

Im finding that parts are hard to come by these days. You might consider ordering the parts and instal them when they arrive. In the mean time run a die down the threads and add some blue lock tights and ride it until the new parts come in.

Helping a friend with a part. They have changed the arrival date several times now they state "unknown arrival time". He has ordered the new part off Ebay and its actually showing up from Japan. The arrival time is 30+ days...... FYI
 

BuellOnYamaha

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That's not a bolt, it's a stud. No need to disassemble the final drive to replace it, just weld a nut onto it and turn it out of the final drive housing. It is probably loctited in there so apply heat to the aluminum housing before turning the stud out. Replace the nut as well, or it will ruin the threads on your new stud.
Got the stud bolt out and ordered a new one. After waiting three weeks, I called the supplier to learn that this part is out of stock everywhere and it could be a month, or a year, before it's available again. I was ale to find the cap nut in stock at my loal Yamaha dealer and grabbed that. I went to a couple of local distributors of specialty fasteners, a couple of auto parts stores, even Ace and True value hoping to find something with the same dimensions but nothing even close. Finally I took my damaged stud to my mechanic and had them recut the threads which did the trick, although if and when the new part comes I will replace it for good measure. Yamaha supply chain seems to be a mess. thanks all for the advice. Should be rolling again today if I didn't just jynx myself by saying that.
 

RCinNC

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With these supply line disruptions affecting the ability to obtain simple things like replacement studs, it's probably a good idea to start Googling "machine shops near me". It would no doubt be expensive to have a machinist make a single stud, or shoulder bolt, or new axle, but at least you'd be able to actually get it in a reasonable amount of time.
 
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