Check chassis fasteners

Home mechanic (basic tools) · Time: 30 to 60 min (estimate) (estimate)

Vibration loosens bolts. A loose axle, handlebar clamp or engine mount can cause a crash; a loose panel bolt causes rattles and lost parts. The K-Light 125 schedule asks for the tightness of all bolts to be inspected at every service. This job works through the bike in order and checks each important fastener with a torque wrench.

Safety

• Bike on the centre stand on level ground.
• Check, do not just tighten harder. Over-tightening strips threads in aluminium and can crack castings.
• Do not touch a brake caliper or brake hose fastener unless you have the confirmed value and will check the brake after.

You need

• A torque wrench and your bike's torque table. Do not move a torque value from one fastener to another, even if they look the same size.
• New split pins, and new self-locking nuts where the manual says to renew them. The K-Light manual asks for new split pins, washers, O-rings and locking plates on reassembly.

How to check a fastener

1. Set the torque wrench to the value for that fastener.
2. Turn slowly in the tightening direction. If the wrench clicks before the fastener moves, it was tight. If it moves, it was loose: tighten to the value and write it down.
3. A fastener found loose twice: find why. Look for a missing washer, a stripped thread, a crack, or a worn rubber mount.
4. Mark checked fasteners with a paint line across the bolt head and the part. A broken line later shows movement. A nut scraped by its lock washer shows the washer has been working: replace it, and see Nuts and bolts keep coming loose.
5. Where several bolts hold one part, tighten in a criss-cross pattern in two or three stages, larger bolts first, smaller last.

Order to work through

1. Front: axle nut and split pin, axle pinch bolts, mudguard bolts, handlebar clamps, mirrors (Tighten and adjust mirrors), lever perches, headlight and indicator mounts. Steering head play: Check the steering head bearings.
2. Middle: engine mounts (Check engine mounting bolts), footpegs and brake pedal (Service footpegs and foot pedals), gear lever clamp, side stand and centre stand (Check the side stand), exhaust mounts (Check exhaust mounts and heat shields), side panels, seat and tank bolts.
3. Rear: shock mounts, swingarm pivot nut, axle nut and split pin, chain adjusters, sprocket nuts, drum brake torque arm and split pin, rear mudguard, number plate, grab rail and carrier.

Check your work

• Every fastener on the list checked, with values noted. Split pins in place and bent over.
• Short test ride, then look for any broken paint marks.

If it did not fix the problem

• Rattles remain: Find and fix rattles.
• Stripped thread or broken bolt: workshop thread repair or extraction.

Reference values (K-Light 125)

Only values that the K-Light manual gives consistently are listed. The manual's values for the rear axle, swingarm pivot, rear shock top nut, brake calipers, fork clamps and front master cylinder disagree between pages and are not given here: confirm them before touching those fasteners.