Front derailleur sticking, not shifting. Will soaking in solvent damage parts? 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?

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!