rounded off chain tensioner lock nut on 250f

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May 30, 2002
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#1
i cant belive i was stupid enough to do this but i did, i just got new michelin m12's put on and was doing some other work on the bike and i rushing to get finished working on the bike so i could test them because it was going to be dark in a few hours. it is the nut that i rounded off, not the bolt. i think i tighened the nut up a little to tight last time i adjusted the chain, i tried vice-grips to get it to come loose and i really made it worse now doing that, i dont know what to do. if i dont come up with something i guess im going to have to take the whole swing arm off and take it to the machine shop up the road and see if he can do anything. if anyone has any ideas please let me know, im desperate here. i was really looking forward to trying out those new tires too.
 

biglou

#2
Take the rear wheel off and use a socket and extension to get on the bolt. Loosen it and the nut will come with it. Remove the bolt completely from the swingarm and replace the nut. Use the correct replacement nut, too: a flanged one so you don't dig into the swingarm.

A little tip-I always shoot some silicone or penetrating oil on the adjustment bolt threads each time I do any rear wheel maintenance. Keeps things from seizing up. Well, so far, anyway.
 
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#3
thanks for responding big lou. its really frustrating because i can only get the open end of a wrench on nut. i thought about maybe getting one of my cheap wrenches and grinding the closed end enough so it would fit in there. the socket might work but im going to have to cut the bolt so i can get the socket on there, even with a deep well socket its still too long. i really dont want to cut the nut and bolt out because then im going to have to use some kind of an extractor to get the remaining part of the bolt that is threaded into the swing arm out.
 

evenslower

N. Texas SP
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#4
Read Lou's post again wolfster, put a socket on the BOLT and the nut will come with it.

There's always the Dremel and/or chisel method on the nut just cut it into pieces and replace the nut once destroyed. Probably damage the bolt in the process. I've rounded off the OEM bolts on my 250f before as well. They seem pretty soft and the fact that you're always putting an open ended wrench on them only makes it worse. Buy a few extra and replace them before they get too bad next time. As Lou also said, something along the lines of anti-seize on the bolt threads will save you a lot of trouble later.
 

biglou

#5
Lonewolf-Put the socket on the bolt head. If can't turn it with a fair amount of force, stop. Try putting your vice grips on the nut AND the socket on the bolt head and then turn them both at the same time. Once the nut backs away from the swingarm the bolt should turn out. It the bolt is hard to remove all the way, use some silicone or penetrating oil on the threads, run it back in without tightening it, then back it out. Repeat that process until you have the bolt in your hand. If the nut spins freely on the bolt, back it up against the bolt head so you can "chase" the threads in the swingarm using the oiled bolt threads as a sort of tap. Take your time, let the oil soak if necessary. You don't want to booger up the threads in the swingarm. Once you get the bolt out, head for the hardware store and find a replacement for the nut and maybe the bolt, too. Most hardware stores should have stainless steel metric hardware available. Cost will be a couple bucks.

This would be a great time for new hardware and some oil on the othe side of the swingarm, as well.
 
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#6
i did reread your post big lou and i understood what you were saying. sometimes i freak out and i dont think clearly at all, im actually embarassed that i couldnt figure out how to get that nut off myself, it was pretty much common sense how to get that out. i dont know what it is sometimes i just dont think clearly, anyway its out and the new one is in, thanks again.
 
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Oct 8, 2002
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#7
I had the same problem with my YZ 125, I was eventually able to get it off by taking the rear wheel off and using a deep well socket on the bolt which in turn got the nut off as well. You might have some success if you carefully heat the nut and bolt with a propane, or Mapp torch then trying to loosen it. When you get it off, save yourself some aggravation and antiseize the threads thoroughly. Good Luck.