I have a set of K SSCs. I guess the previous owner took them to a bike shop where the dude injected some thick oil in the freewheel, so that now it doesn't freewheel much. Not a big deal, probably doesn't affect the performance, but I would like to clean the freewheel. What should I clean, what solvent or other stuff should I use ? How to relube or regrease the thing afterwards ?