Crank coming loose
 

So I picked up a big schwinn circuit (I have now had 3). Put some regular handlebars on it, new tires and cables, and pawned it off on a tall friend of mine.

The friend now tells me that when he rides it a crank starts coming loose. He tightens it up, but it keeps coming loose. I think this is the non-drive side crank, but I am not sure.

I haven't had a chance to look at since he told me about it. He lives a ways away, and is not very mechanically inclined. I am not sure what to tell him to look for, or what to try.

So, what is the likely problem here? Stripped threads?

What is the cheap and easy solution to the problem? Loctite? Which color?

Jared

obligatory picture of said circuit:

http://i624.photobucket.com/albums/t..._0165Large.jpg

PS-- the lugs and wheels are black because the previous owner painted them. Or took a sharpie to them. Not sure what he was thinking

A new crank arm. The taper hole is toast if it's been ridden loose.

Hold it, there could be a washer missing and the bolt is bottomed out. It still may be toast, but I got one in on trade that had that problem, and I put a washer in it, tightened right up and no problems since.

It could be a number of things:

1. Most likely it has ridden with loose crankarm for a while and the taper is damaged, in which the crankarm is toast. However, sometimes it is simply a small burr that has been created in the tapered hole by the end of the spindle. Simply filing this down sometimes solves the problem, if the bicycle was not ridden for any extended periods with a loose crankarm.

2. It could be an incompatible spindle. The back of the crankarm could be sitting against the spindle shoulder, allowing it to go on no further, or the bottom of the extractor hole may be flush against the end of the spindle.

3. The crankarm may be cracked, radiating out from the spindle hole.

4. As previously suggested, the crank bolt may be bottoming out in the spindle.