Barrettscv 

I've got s box of fully functional vintage derailleurs that have been removed from older bikes. Some of these have the usual combination of chain lube and road debris & dust that needs to be removed.

I don't like the prospect of using solvents since the pivot points should not be compromised.

What do you use to clean dirty derailleurs?

plonz 

I remove the jockeys and cycle it through the ultrasonic cleaner. I use a small bit of Branson cleaner solution with it. Gets everything loose enough to clean up with small brushes and wipes. Someone may come along asserting this is the worst method one could possibly use but it’s worked well for me.

Spaghetti Legs 

Good wipe down, spray and wipe with WD40 and I know it’s not supposed to work, but I’ve found soaking aluminum bits in Evaporust followed by a water rinse and dry makes them super shiny.

That might have been the longest sentence I’ve ever written.

cyccommute 

Although I’m not a fan of Simple Green for chain cleaning, it does work well for cleaning surface grim. Spray it on the derailer, let it sit for a while, and spray it off with a hose. Works quite well. I’d avoid any kind of soaking in solvents or using ultrasonic baths as there are lubricated parts in the A and B knuckle that are difficult to disassemble and relubricate.

Mr. 66

I'll use auto tire and wheel cleaner with a bristle brush. Works good, it's not a degreaser, it will take off crust and dirt. I'll use the stuff on brakes, rims derailleurs. It may take a couple or few applications.

This Suntour was on a bike that was 40 years stored uncleaned in an attic. One could chip the old grease, the cage pivot was seized.
Used here on a dirty set of brakes now spankin' clean.


I wouldn't worry about lube, the old stuff will need lube no matter how you clean.

RustyJames 

Warm soapy water and a toothbrush work for me. Some times I’ll use a wood skewer and cloth to get to crevices, etc.

LittleGinseng 

This^. If I have the time (and I usually do) I'll disassemble the bits that are easily removable, clean, and reassemble.
A final wipedown and polish with Turtle Wax Carnauba and it's done.

ThermionicScott 

Beyond a certain point of age, use, and/or filthiness, it's probably best to tear the RD down as completely as possible for cleaning and relubing. "RJ the Bike Guy" has some good YouTube videos for tearing down RDs. The rivetted pins on Shimano (and probably other brand) RDs mean that you can't take them completely to pieces, but once all the other stuff is out of the way, it's not as hard to clean them and work some light oil into the pivot pins.

SurferRosa

WD-40 and fully overhaul with fresh grease.

sloar 

Soak in hot water and Dawn dish soap. I usually leave them in for a few hours. Scrub with a soft brush and dry with an air hose. Works great.

Chombi1 

A good soaking in mineral spirits and blasting with WD40 and scrubbing with an old toothbrush works very well. All the time.
Also breaking down the derailleur to its individual parts helps get into all the nooks and crannies where gunk and grit hides.....

3alarmer 

.
...if I were doing a bunch of them at the same time, I'd disassemble the pulley cages, and pull the bushings out of them, put them in individual sealed baggies with a solution of 50//50 Simple Green or the purple stuff they sell, and toss them all in the ultrasonic. For one at a time on projects, I keep a wide mouth short jar from my wife's skin care stuff (picked out of the recycling trash) filled with mineral spirits. For that I do the same level of dismantling. Reassemble with fresh grease in the pulley bushings. Re-lubricate the parallelogram pivots with Tri Flow. Made sure you re-lubricate the internal springs at the top and (if present) lower spring pivots as well.

rjhammett

This probably fits into the solvent category but I use mineral spirits to clean derailleurs. I spray it on, use a toothbrush to get off the gunk then wipe it down. I do not let the derailleurs soak in the stuff.