The reservoir pries off the cylinder with a bit of a struggle. I used straight Castrol Super Clean (or brake cleaner, ed) and two packs of BB gun BB's as agitators to clean the inside of mine. Block off the nipples with duct tape, fill the res about 25% full of SC, add the BB's and put on some Mambo music. The cleaner will foam-up and reduce the contact effect of the BB's internally, so several flushes are necessary. Finally, rinse well with water, blow out, and let dry. Mine looks like new.