Originally Posted by
Duragrouch
If the chain is contaminated with dust or dirt, agitation is an important part of cleaning. Even if not dirty, what makes oil lubricant turn to a paste consistency, is that the ultra-fine metal wear particles from the chain, form a colloidal suspension within the oil. A proper chain cleaning needs to remove all of that, including inside the chain.
BUT... you need not remove the chain. The following is way easier than removing the chain (the harder part is threading it back through the rear derailleur and getting back together with a chain tool, it helps to leave a bit of pin exposed inside the outer chain plate to "snap" the chain back together to hold it while you use the chain tool. But this is easier.). Park Tool originated the "on-bike chain cleaner", but now there are similar ones on the market at a fraction of the price (Park was orginally $40 I think), copies can be had off amazon for about $10 I think. You fill the cleaner up to the fill mark (about halfway I think) with a solvent; I use surplus tiki torch fuel (98% mineral oil) because mostly full bottles are dirt cheap at goodwill at the end of the season, and it acts as a mild solvent for my chain lube, 75W-90 gear lube. You snap the cleaner around the chain between the crank and rear derailleur. You crank the crank backwards. The cleaner has several wheels inside to force the chain through a serpentine route, which is sufficient agitation to clean the insides. Actually, what I do is crank so the full chain passes through the cleaner a couple times, then let it hang on the chain and walk away for a half-hour or more to do something else, that gives time for the solvent to work. Then I crank a good number of times, and remove the cleaner. I used to use fresh solvent each time, but now I just dip a magnet into the solvent, stir, and pull out all the metal sludge, leaving the solvent, not clean, but reusable. I give the chain a wipe, but also leave it a day to dry further, the mineral oil takes about a day to dry out. Then lube.
Use the cleaner above in a place such that, if you tip the cleaner and dirty oil comes out, you don't ruin a carpet or such. Even concrete will get stained. Ideally, outside over dirt or put a dropcloth or cardboard underneath.