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I've got an older deore lx front derailleur for a mountain triple crankset. It wasn't shifting properly, and it seems that it's sticking and not returning back to a neutral position when I shift it. I've tried loosening both limit screws with no change in behavior. I took it off the bike and tried to move the derailler as if I was shifting, but doing that moves the cage, but it doesn't try to return to the original position.

I'd like to soak the derailleur in a cleaning solvent (such as kerosene or paint thinner) to remove any gunk that may have built up on inner surfaces. Should I worry about the solvent damaging parts? Is there anything else to try to revive the stuck derailleur?

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3 Answers

up vote 3 down vote accepted

Kerosene, gasoline and diesel are fine, because I have used them extensively for years without any problem (I recommend only kerosene, much better than diesel or gasoline).

The symptoms you describe are a bit odd. Does the spring have enough tension? Is the cage bent in some way?

Try the soaking + toothbrushing + lube approach, most probably you'll solve the problem or get a better inside. No fear of chemical damage, whatsoever, even if you leave it on the bike and brush the frame, too.

Hope this helps!

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And if that doesn't work, you can light it on fire. –  user973810 Sep 27 '12 at 17:39
    
"solve" the problem, pun unintended... If you light it on fire, remove the bike from inside it first! –  heltonbiker Sep 27 '12 at 19:45
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So long as it's a good-quality derailer, any common solvent (gasoline, kerosene, diesel, parts cleaner) should be fine (though obviously some are worse than others with regard to the fire/explosion potential).

The danger (other than explosion) would be with a cheap derailer that contains plastic parts (eg, bushings) that are not resistant to petroleum solvents.

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In some derailleurs such as Shimano Tiagra, a small metal nub against which the spring presses is prone to breaking off. In such case there won't be any tension on the spring which could explain the symptoms you're experiencing.

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