Check the swingarm pivot

Home mechanic (basic tools) · Time: 20 to 45 min (editorial estimate) (estimate)

The swingarm is the arm that holds the rear wheel and swings up and down on a pivot shaft through the frame. On most small bikes the pivot runs in plain bushes (sleeves); some bikes use needle roller bearings. Worn bushes let the rear wheel move sideways, which makes the bike weave, wear the chain unevenly and clunk. This check finds play and stiffness.

Safety

• Support the bike so the rear wheel is off the ground and the bike cannot fall forward.
• If the swingarm moves sideways at the pivot, do not ride. The rear wheel can steer the bike.

You need

• A helper, and the bike on its centre stand or a paddock stand.
• The pivot nut torque for your bike. No value is given here: the K-Light 125 manual lists two different pivot nut torques.

Steps

1. Check the rear wheel bearings first, or you will confuse the two: Check wheel bearings.
2. Stand behind the bike. Hold the rear end of the swingarm (not the wheel) on both sides and pull it firmly left and right.
3. Your helper puts a finger over the joint between swingarm and frame at the pivot on each side. Any knock or movement there means worn bushes or a loose pivot nut.
4. Check the pivot nut is tight with a spanner. A loose nut feels like worn bushes. Tighten only to the model torque, then repeat step 2.
5. Look at the chain slider (rubbing block on the swingarm) and the chain guide: heavy wear on one side suggests the swingarm or wheel is out of line.
6. Up and down movement: on a twin-shock bike, a workshop or skilled home mechanic can remove the lower shock bolts with the wheel supported, then lift the swingarm through its travel. It should move smoothly with no tight spots. Refit the shocks.
7. If grease nipples are fitted on the pivot, grease them until clean grease shows.
8. Look along the swingarm for cracks at welds and bends, especially after a crash.

Check your work

• No sideways movement at the pivot with the nut tight.
• Smooth, quiet up and down movement.

If it did not fix the problem

• Play remains with the nut tight: the bushes or pivot shaft are worn. Replacing them means removing the rear wheel, shocks and swingarm, pressing out the bushes and checking the pivot shaft for bend (K-Light 125 limit: 0.2 mm runout; never straighten it). This is workshop work unless you have a press and the manual.
• Swingarm bent or cracked: Inspect the frame after a crash.

Reference values (K-Light 125)