Have a problem with one of my forks and/or fork top bolts.  Took the forks off to change out the oil today.  One of the top bolts came right out, the other took a fair bit of force on the wrench.  It came off without too much trouble but I noted some fine shavings (for lack of a better term) on the threads. 

This bolt does not want to go back into the fork tube.  It'll get 2 turns in, then get stuck.  I don't believe it's cross threaded, I'm pretty sure I have it in straight. 

I've gone through the threads with my thumbnail and it's pretty smooth and my thumbnail progresses along the threads just fine.  Likewise with the inside of the fork tube, though there is one bit of a rough spot just a thread or two down. 

Another piece of info - the "bad" bolt wont go into the "good" fork and the "good" bolt wont go into the "bad fork".

Any thoughts?  Should I start fork shopping, or is this something I (or a competent mechanic) could fix?  Thanks,

jeff

A thread file might be able to fix the threads, but I'd be concerned about filing the fork body, since the shavings are going to end up in the oil.

Haven't put the new oil in yet.  Never heard of a thread file but googled it, think I understand. Two questions - any idea what would be the proper size for this part?  And is there a comparable tool (or can these be used) on internal threads?  Thanks,

jeff

At the bottom of this page: http://www.jtsmach.com/jtswebshop/Taps_Dies/T224.asp

Thanks!  So I should probably get metric file and the metric internal thread cleaner/restorer and do both.  Anybody know what the pitch on these parts is?  The tools on that page work from 0.75 up to 3.0. 

jeff

You can measure the threads with a micrometer and average them to get a thread pitch, or you could go to your local hardware store and buy a thread gauge. The gauge is pretty handy for buying fasteners, and is dead simple to use.

Hi Jeff
What a bugger. I guess you came across the webbikeworld article at:
http://www.webbikeworld.com/motorcycle-tools/thread-file/
on how to use these files - couple of good pics/diagrams. . I've never used one on an internal thread but the file works well on bolts. Re swarf: I guess if I was working internally I'd be plugging up the tube with well greased waste and pulling that up as a solid lump. If the fork tube was off, working with it inverted would be the ticket. Good luck, you'll be fine with the job.

Got the internal thread cleaner/restoring tool in the mail today.  Used it on the fork tube (used a little fork oil for lube/debris catching), to no apparent benefit.  The bolt stops at exactly the same point. 

The tool moved smoothly through the threads (they're 1mm btw), and did clean out some gunk that was in there, but overall I think they were probably OK to begin with.  Note, the "cutters" for this tool don't really seem to cut, I believe they do more in the way of reshaping vs actual cutting like a tap would. 

Thread file is likely

Got 'em back together. I have to admit there was a point about 2 hours ago that I thought I was screwed.

The thread file showed up in the mail so I took a break from teleworking and got to work.  The threads on the bolt seemed quite fine to begin with but I dutifully ran the file on them and tried to screw it back into the fork. No dice, same 2.5 turns as before.  So I figure I'll take it to a local shop and ask them to look at it.

The guy has a look, says there's a problem with the internal threads (d'uh) and takes it back to the mechanic.  Comes back after a few minutes and says they don't think it's repairable.  Points to the bottom of the threaded portion where it really does look messed up, like there's whole threads missing.  Now, I can tell that when the bolt is all the way in it won't even get that deep in the fork, but whatever.  They weren't going to solve it.

So I came back and decide that if my only other solution is to get a new fork tube, I may as well get the internal thread restorer out and really go to town.  Worst case I really do kill it and have to buy a new one anyway.  

So I run the restorer in and out several times, each time going through and cleaning out the threads as best I can with a thumbnail.  The directions on the restorer say to use "light pressure" but I was squeezing it pretty hard.  What do you know, now the bolt went in about 5 turns.  Emboldened, I keep at it with the restorer and damned if the bolt doesn't go all the way in now, relatively easy with a wrench.  

So it's all back together, after I finish up a little work and a victory beer   I'll go put the bike back together.

Problem solved and I have a few handy new tools.  Thanks for the advice.

jeff

Well done, Jeff. Your patient approach really paid dividends here. Those thread restorer files will be a life time addition to the tool kit!