Doing the ordinary clean, degrease and lube to freewheel is the best way to maintain freewheels.
What you need:
Something to open the wheel (may use an old Philips screwdriver)
A tray (very important)
Step 1: Opening the Freewheel
When opening freewheel, you should be careful and do it slowly. If needed, use a hammer to tap the screwdriver gently till it starts to move. Afterward, put it on top of your tray.
Step2: Clean the Bearings
Carefully take the casing of freewheel out and let the bearings drop in the tray. Take the rest of them and put them in the tray for cleaning (in order to clean them, you can put them inside the rag and scrubbed them clean)
Step 3: Disassemble the Freewheel
Took the rest of the freewheel apart and cleaned everything
Step 4: Clean the Body of the Freewheel
Just use your pad and scrub everything really gentle till it's clean
Step 5: Reassembling
Start reassembling everything in the inverse order you disassembled
Step 6: Reassembling the Bearings
Put the grease in the lower place for the bearings and start ''gluing'' the little balls there (keep a little bit of grease in your fingertip and use it to put the bearings in place)
Step 7: Reassembling the Cassette to the Wheel
With the metal pieces in the right position slowly insert the cassette while turn it counter-clockwise till it gets in place
Step 8: Rest of the Bearings and Close
Once again grease everything and add the balls. Put the cover slowly once again and tap it lightly till it feels firm again and you got a clean freewheel again.
Generally, the best way to clean your cassette is to take it off, bath, and scrub it in a degreaser solution. But when you are lazy or don’t have much free time to do that, a quick result is needed. Also, you may use some product hacks that will make your life easier, and keep your cassette shinier.
Before starting the quick clean, you should definitely make sure that you have cleaned and lubed your chain and your chain rings first. Otherwise, your freshly cleaned cassette will get a brand new coating of whatever junk was already in the chain and rings.
An old toothbrush
A shop rag or microfiber cloth
Degreaser – choose your favorite kind
Cleaning your cassette without bothering to remove it
Remove the wheel
Pick your favorite cleaning tool, and get it soaked with degreaser. Not too soaked, but enough to help break up the grime.
Lay the wheel down flat, cassette up. With a shop apron on, you can just put the wheel in your lap. Do what’s most comfortable to you.
Start at the biggest sprocket, and work the rag (or shoelace/floss, etc.) all the way in toward the hub. The technique here lies in working with the freehub–pull your rag left to collect the grime and then right to move to a new section of the cassette.
Repeat between each sprocket until you’ve got the whole cassette cleaned up and shiny again.
Replace your wheel (after you’ve cleaned the chain), lube your chain, and you’re good to go.
Then, you finish.
Note: it’s generally best to do this maintenance after a ride, and let your bike sit overnight before riding it–you don’t want to ride your best friends filled with all the road muck.
Click here to see the video of HOW TO CLEAN, DEGREASE, LUBE A BIKE FREEWHEEL.