Inspect and replace clutch plates and springs

A wet multi-plate clutch is a stack of friction plates (with a lining) and plain steel plates, squeezed together by springs. Friction plates wear thin, springs get weak and steel plates warp from heat. This page is an assessment and hand-off: it tells you what to rule out first, what the workshop will open and measure, and what to ask for. Opening the clutch needs special holding tools and a new cover gasket, so it is not a home job.

Safety

• Do not keep riding a slipping clutch. It overheats the oil and the debris from burnt plates goes round the engine.
• Hot oil burns. The workshop should drain the oil cold or warm, not hot.
• Spring bolts must come out evenly, a little at a time, in a criss-cross order. Removing them one by one leaves the last bolt holding all the spring force and can break the lifter plate.

Rule these out first (rider or home)

• Free play correct: Adjust clutch lever free play.
• Cable slides freely, lever returns: Replace the clutch cable.
• Oil level correct and the right grade for a wet clutch: Check the engine oil level. The K-Light manual says oil level and viscosity affect clutch action, so check them before opening the clutch. Some car oils are not suitable for a wet clutch; use the type in your manual.
• If all are good and the fault remains, the clutch needs opening.

What the workshop will do

1. Drain the engine oil. On the K-Light the engine stays in the frame.
2. Remove the right-hand engine cover and the clutch spring bolts, evenly and in a criss-cross order.
3. Lift out the lifter plate, springs, release bearing and pushrod or push lever.
4. Hold the clutch with a holding tool and remove the centre nut, then the hub, plates, pressure plate and outer basket. Keep the plates in order; their order and the way they face both matter.
5. Measure each friction plate with a vernier in several places. K-Light 125: replace below 2.6 mm (standard 2.9 to 3 mm).
6. Measure each spring's free length. K-Light 125: replace below 34.2 mm (standard 35.45 to 36.5 mm). If one spring is short, replace them all.
7. Lay each steel plate on a surface plate and try a feeler gauge under it to check for warp. Use the limit in your bike's manual; the K-Light manual does not give one.
8. Check the basket slots and hub splines for notches. Small burrs can be dressed with a file; deep notches mean a new part, because they make the plates catch and cause judder and drag.
9. Check the pressure plate face, the release bearing (it should spin smoothly) and the pushrod.
10. Fit new parts as a complete set: friction plates, steels if warped, and springs. Soak new friction plates in clean engine oil before fitting.
11. Refit with a new cover gasket, tighten the nut and bolts to the manual's torques, refill the oil and set the lever free play.

What to ask for

• Each plate and spring measurement written next to the limit, and the old parts shown to you.
• Whether the basket, hub and release bearing were checked, and which oil was used.

Do not attempt at home without the manual

• Do not hold the clutch by jamming a screwdriver or the gears; use the holding tool. Do not mix old and new springs.

If it did not fix the problem

• Still slipping with new plates: check the oil type again and the free play, and ask the workshop to check the lifter is not sticking.
• Still dragging: Clutch drags; the workshop should check the basket, hub and pushrod.
• Noise remains: Rattle or whir from the clutch.

Reference values (K-Light 125)