A newly fixed link will often be stiff because the process of pushing through the rivet has jammed the chain plates together. You may also find that stiff links develop while you’re out riding. Heavy rain can do it, as can cycling through rivers. You can feel a stiff link when you pedal with moderate pressure – the chain regularly slips a little, enough to annoy you, but not always at the same point in the pedal stroke.
To locate the stiff link, lean your bike up against a wall with the chain in the big chainring at the front and the small sprocket at the back. Pedal slowly backward with your right hand and watch the chain as it feeds out of the bottom of the cassette, around the jockey wheels, and off the bottom of the bottom jockey. You see the bottom jockey wheel skip forward as the stiff link passes through the rear derailleur. Keep pedalling backward, and allow
Step 1: Once you’ve found the stiff link, look at it carefully from above. You may find that one side of the rivet pokes out of the side of the chain more than the other. If this is the case, use the chain tool from the side that sticks out more to even it up.
Step 2: Lay the chain over the supports nearest the handle of the tool with the sticking-out end of the rivet nearest the handle. Wind in the handle until it lines up exactly with the centre of the stiff rivet and touches it. Carefully wind in the handle another third of a turn. If the link is still stiff, repeat from the other side of the chain.
Step 3: If you don’t have a chain tool, hold the chain in both hands, with the stiff link in the middle. Put both thumbs on the stiff link and flex the chain gently backwards and forwards. You should feel the stiff link gradually loosen off. Don’t overdo it though – you don’t want to end up twisting the chain.
“The chain regularly slips a little, enough to annoy you, but not always at the same point”
An easier way of joining chains is with a Powerlink. Both ends of the chain must be narrow segments, so remove any wide segments with a chain tool. Drop the chain off the chainring into the gap between the chainset and the frame for slack. Fit half of the joining link onto each end of the chain, one facing toward you and one facing away from you. Each part of the joining link has a key-shaped hole. Push one half into the other, then pull the two sections of chain apart to lock them into place. Replace the chain on the chainring. To remove the Powerlink, push the links on either side of the joining link toward each other. You may also need to squeeze the plates of the link together – one of those tricky moves that would be easier if you had three hands. The Powerlink rivets should pop back into the inner part of the key-shaped hole, allowing you to separate the chain by pushing half away from you and half towards you. Powerlinks are not designed to be used with Shimano chains.
Pull apart Powerlink to lock
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Shimano chains”