Mountain Bike Rear Sprocket Slipping

If the chain is worn out replace it.
Mountain bike rear sprocket slipping. Step 1 make sure that the problem is caused by the freewheel. Skipping can also be cause by a worn chain worn chainrings and worn sprockets step 2 remove the rear wheel. If a link is bent either replace the link or the entire chain. I guess that the spring isn t hold the sprocket well.
The best is to bring the bike to shop to repair it. If not check cable housings chain and cogs for wear and see if the rear derailleur arm is bent. Look over the chain for excess wear or bent links. Disconnect the rear brake and undo the axle nuts step 3 remove the cassette.
The freewheel mechanism is contained inside the splined housing. Stop those bike gears slipping simple tightening of the gear cable with an anti clockwise turn of the barrel adjuster usually resolves most gear changing problems. But if you want to repair it all alone first get your rear wheel off get the sprocket off and check the 3 teeth inside the sprocket they have to be perfect half circles.