Twisted links are usually victims of clumsy gear shifts, although they may be caused by trailside objects hitting the chain, too. You feel twisted links first a regular, slight chain slip but not on every pedal stroke it’s important to fix them quickly to avoid more serious damage to your chain and derailleur.
Twisted links (A) can cause the chain to kink
The gaps between the chain plates are only just big enough to fit a sprocket or chainring tooth into, so once a link is twisted it usually rides up over the tops of the teeth rather than dropping into the valley, causing your chain to slip under pressure. Alternatively, if the twisted link does mesh successfully onto a chainring tooth, it can get stuck and be sucked around the back of the chainring, getting jammed between the chainstay and the chainring. As well as being annoying, this damages the chainring and chainstay.
Even after you’ve worked out that you have a twisted link, it can be tricky to spot. The best place to see one from is behind the bike. Get someone else to hold the bike upright and pedal slowly backward. Get behind the bike and look along the chain from the same level as the cassette. You should see the chain stretching away from you, from the top of the cassette to the top of a chainring. The links should all be in the same line, with the two sides parallel. As your friend pedals, fresh chain is constantly fed up through the derailleur. Keep watching the top section of chain; the twisted link will make an obvious kink in the straight line of the chain.
You have two options for sorting out the twisted link. The easiest is to re-twist the link straight again. If it works, this solution is quick and simple, but leaves the repaired link weaker. You need an Allen key and a small screwdriver, or any other combination of two small pointy things. Insert one on either side of the twisted link and gently ease the chain back until it’s straight. Try to straighten the link in one movement because working it backward and forward weakens the metal. If you have a chain tool, a better option is to remove the twisted link for a permanent repair. This will shorten your chain, so check first that your chain will still be long enough to go around the big sprocket at the back and the big chainring at the front. If you shorten it too much and then shift into this gear, you risk damaging the rear derailleur and the part of the frame that it bolts onto. Check that you have sufficient length to remove a link by shifting into the largest sprocket and chainring. Looking at the bottom of your chainring, identify the last chain link that’s meshed onto a chainring tooth. Holding the pedals still and making sure that the rest of the chain stays wrapped around the chainring, pull this last link downward so that it releases from the valley between the two teeth. Move it anti-clockwise around the chainring and fit it back into the next-but-one valley. As you do this, watch the rear derailleur. Shortening the chain like this will drag the lower (tension) jockey wheel forwards. Hold the chain in this position and push the bottom jockey wheel upwards. If there’s still enough slack in the chain for you to push it up 10mm (1⁄2 inch), then you can safely remove the twisted link. As with rejoining broken chains, if you have to reduce the length of the chain beyond what you need to reach around the big chainring and sprocket, adjust the “low” end-stop screw on the rear derailleur so that you cannot shift accidentally into this gear combination. Shift into the largest sprocket that the chain will comfortably reach, then screw the “L” end-stop screw in until you feel resistance.
Remove one complete link
Find the twisted link, as above. You will need to remove a complete link – one wide section and one narrow section. Use the instructions to split the chain twice, once on either side of the twist. The remaining ends of the chain should be different – one wide and one narrow end. For standard, non-Shimano chains, the wide section should still have the rivet sticking out of one side. Use this to rejoin the ends of the chain. For Shimano chains, use a special replacement rivet to rejoin the two ends of the chain. New chains are always supplied much longer than you will ever need them so that you can be sure to have enough. When fitting a new chain, always make it long enough so that you can safely take a link out in an emergency.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES