Once your mountain bike chain becomes damaged, you should immediately replace it with a new one. It is possible however, to repair a broken chain using a chain tool. For this very reason, most mountain bikers travel with a chain tool.
Your chain has three basic components – the metal side plates, the rollers between the side plates, and the rivets, or pins which go through the rollers and help to hold the plates together. These pins allow the rollers to freely turn as the chain moves around the cogs.
If your chain happens to break, you’ll need to remove the broken link and replace it with a spare link. To do this, simply reattach the two ends of the broken chain and ride on a shorter chain until you can get it replaced.
To remove a broken link of chain, place it in the chain tool. Now, turn the tool counter clockwise until the rivet pin of the chain tool touches the chain rivet. Continue to turn the tool until the pin pushes out of the roller. Be very careful, as you want to stop turning when the pin is right at the edge of the roller, before it moves through the outer side plate.
Now, turn the tool in the other direction, and back it...