I didn’t know my clutch needed servicing...
Every part of a bike needs some TLC at some point to keep it working correctly. This can vary from a simple adjustment, to a complete rebuild – your bike’s clutch is no exception.
So how do I know if there’s a problem?
Problems that only manifest themselves gradually are sometimes hard to spot if you are continually riding the bike. However, if you do notice things like a stiffening clutch lever; gear selection becomes increasingly difficult; the bike stalls with the clutch lever pulled at the lights; or the revs climb but with limited forward movement (clutch slip), then you’ve got problems. Metallic chattering or rumbling at a standstill from the clutch casing usually signifies wear in the clutch basket.
What are the most common problems?
Strange but true, oil level and incorrect cable adjustment are the biggest factors in clutch aggro. Wet clutches are the most common type of clutch (so-called because the clutch runs in oil to keep cool) but too much oil will drown the clutch’s drive friction plates causing them to slip. A clutch lever with excessive free play will cause premature wear because the clutch doesn’t fully disengage when the lever is pulled. Clutches are also designed to handle a set of amount of power, so upping your bike’s output can place great strain on a clutch unless it’s uprated – stronger springs, performance clutch plates etc.
Are all bikes prone to problems?
Yes, but some more than others. Older models with heavy mileage will mean the clutch components will be worn. Bikes frequently used on trackdays will suffer from premature wear. And despite upgraded components, race bike clutches get hammered more than most.
Why do some bikes have hydraulic clutches and some cable?
High performance motorcycles traditionally have cable-operated clutches because they give the rider more feel through the fingers and are generally quicker in action. However, modern hydraulic systems offer self-adjustment, and are now considered almost as refined as cable control systems.
1. Correct cable adjustment is very important. A slack cable (too much play in the lever) won’t allow the clutch to fully disengage. Over-tightening will mean not enough tension on the clutch springs – resulting in clutch slip. Ideal play should be 4-5mm at the end of the lever.
2. Cables stretch, clutch plates wear and springs lose their strength through heat and constant compression and release. Due to these reasons cable free play adjustment at the lever soon runs out. Sometimes a secondary adjuster is located nearer the engine. Set the lever adjuster to minimum before taking up slack with the lower one.
3. Hydraulically-operated clutches self-adjust but still need maintaining. The master cylinder fluid needs to be changed on a regular basis – more than once a year – as the fluid breaks down with pressure and heat build-up. If the fluid looks dirty, change it. Oil or grease on the lever’s pivot keeps an easy action.
4. Hydraulic clutches have a secondary (slave) cylinder to activate the clutch pushrod to disengage the clutch. Treat it like a brake caliper: bleed it regularly, remove and clean around the outer wall of the piston. Replacing the clutch hose for a braided steel item increases feel at the lever and gives full piston movement as it won’t expand.
5. If the clutch slips and every available adjustment is spot on, and the cable isn’t sticking, then it’s time to investigate the clutch. Before removing any parts it is important you get a replacement clutch casing gasket – you can’t guarantee the old gasket will come away in one piece to be used again and they are only £6-7.
6. Drain the old engine oil and remove the filter as they may be contaminated with clutch friction plate debris – you could also tip the bike on its side to prevent oil loss. Remove the clutch cable from its actuator or remove the slave cylinder before removing the outer clutch casing to make life easier.
7. The clutch plates are held in place with bolts that also retain the clutch springs. Undo the bolts to remove the springs. Check for correct tension by measuring their length against specs given in the workshop manual. Stronger replacements are available. A temporary cure is to fit small washers under the bolt heads.
8. Remove the clutch plates, which are a mixture of friction and plain steel plates. They are installed in sequence, so make a note on the order in which they come out so when the clutch is rebuilt they go back in the right way. Measure the friction plates with a vernier caliper as per manual specifications. As a rule if the plates smell burnt…
9. …And are obviously toasted then they are buggered and should be thrown away – new plates are the only option. You can get original plates from the manufacturer, or buy quality replacement plates for less. All new plates should be liberally coated with fresh oil, the same type used to fill or top up the motor to ensure they don’t stick.
10. The steel plates also suffer from heat and can end up warped. Check each plate for blueing – a sign of overheating, or for irregular scuff marks on the circumference of the plate – signs of warping. You can also wipe them free of oil and lay them on a sheet of glass to see if they’re flat. In all cases of wear they should be replaced.
11. With the clutch stripped, check the clutch basket (where the plates sit) for signs of wear. Where the clutch plate alignment tabs sit on the clutch basket fingers it causes wear – more so on older machines. These marks cause the plates to chatter loudly and filing them smooth will help reduce the noise and improve clutch feel.
12. With the new plates installed, tighten the spring bolts to the correct torque (either manual or dealer supplied). Remove traces of the old casing gasket before fitting the new one, ensuring the alignment dowels are in place. If a crankcase join is seen, smear gasket sealer on for a good seal. Connect the cable/master cylinder and adjust/bleed.