Check chain guides, sliders and guards

Home mechanic (basic tools) · Time: 15 to 30 min (estimate)

A plastic slider on the swingarm stops the chain cutting into the metal. Some bikes also have a guide near the rear sprocket and a chain guard or a full chain case. When the slider wears through, the guard is bent or the wheel is not straight, the chain rubs. That wears the chain and swingarm and can help the chain jump off. On the K-Light 125 the slider and chain cover are fitted on the swingarm.

Safety

• Engine off, key out, bike on the centre stand. Turn the wheel by hand only.
• A chain that has cut into the swingarm weakens it. If you see a deep groove in the metal, have it inspected.

You need

• A torch, spanners and screwdrivers.
• A straight edge or a length of string to check wheel alignment.

Steps

1. Find where the chain touches: look for shiny marks, cut plastic, metal dust or grooves on the slider, swingarm, guard and frame.
2. Check the slack first. A slack chain slaps the slider and guard: Check and adjust chain slack.
3. Check the slider near the swingarm pivot. If it is worn thin, split or missing, replace it. On some bikes it bolts on; on others the swingarm must come out (workshop).
4. Check the chain guard or chain case. Straighten or refit a bent guard so it does not touch the chain anywhere as the wheel turns. Tighten its bolts. K-Light 125 chain cover bolt (M6): 10 to 12 N·m.
5. Check wheel alignment: the marks on both adjusters must match. Lay a straight edge along the rear sprocket face, or sight along the chain from behind: the chain should run straight from the front sprocket to the rear one.
6. Turn the wheel and look at the rear sprocket. A wobbling sprocket pushes the chain sideways (Inspect sprockets).
7. Hold the rear wheel and try to move it side to side, and hold the swingarm and try to move it side to side. Play lets the chain run crooked (Check the swingarm pivot).
8. If a new chain or sprocket was fitted recently, check it is the right width and that the sprockets have the same offset as the originals.

Check your work

• The chain runs straight and touches only the slider surface, which is in good condition.
• No guard, cover or bodywork touches the chain anywhere around the wheel's turn.

If it did not fix the problem

• Chain still rubs: Chain rubs on the guard, slider or swingarm.
• Swingarm has play: Swingarm moves sideways or has play.

Reference values (K-Light 125)