Motorcyclists can be lumped into two groups; the ones that have replaced a clutch and the ones that will replace a clutch. It's really that simple. Clutch plates, which are just a few discs of cork and steel, are all that harness the massive amounts of power from your right wrist.
The clutch is responsible for transferring the power from your engine to the countershaft sprocket, which then feeds it through the drivetrain and into the rear wheel.
Another interesting note about clutches is that in general, having a backup replacement clutch rarely crosses anyone's mind until it's already too late. Be it a botched launch full of foolhardy clutch slip or trying to do a burnout with the clutch partially disengaged, by the time most people discover they need a clutch their old unit is already cooked.
Our Project 2008 R1 had just 6000 miles on the clock, but it also showed all the signs of a smoked clutch; it initially started slipping when the oil was cold (colder oil has a lower viscosity) and eventually it got to the point where any amount of throttle would break the clutch free. With forward movement stagnant, it was time for an upgrade.
But we didn't just want any old replacement unit. A quick call to KG Clutch netted us a complete clutch kit: new steel plates, high performance springs and a set of KG's new Kevlar discs.
A tech specialist at KG explained that a move to Kevlar discs not only increases bite, but longevity as well. We'd also like to point out that the discs aren't made from solid Kevlar, but rather a mix of Kevlar and cork. And it's this special blend of the two that creates the ideal feel. Too much Kevlar and the discs will be so abrasive they'll prematurely wear out the plates. Yet not enough Kevlar and the discs won't have enough bite for high-performance applications.
In addition to the upgraded clutch discs and plates we also stepped up to stiffer springs. An increase in spring pressure further loads the clutch discs and plates for more clamping force. A byproduct of stiffer springs is more lever effort, so in some instances race-style springs with lots of pressure can increase lever pull too much for the street-unless you've got forearms like Popeye. Our KG clutch only marginally increased lever pull.
We used a KG Kevlar clutch kit on our 9-second ZX-6R drag bike recently and it withstood over 50 passes in a day-many of which entailed launching at over 12,000 RPM. Needless to say, just a few hard passes on a stock clutch and it's history.
Installation of the KG clutch in our R1 was a simple remove-and-replace affair. Before diving in though, it's always a good idea to soak the new clutch plates in oil for 10-15 minutes. This is done to prevent scoring when the bike fires up with dry discs for the first time.
After draining the oil, remove the clutch cover followed by the pressure plate and the stack of clutch discs/plates. Simply install the KG counterparts, button everything back up and add new oil. Be sure to count the order and number of plates/discs so the KG hardware is accurately installed in the same manner as the stock plates.
Once the KG kit was installed we took it easy on the new pieces for 50 miles and then dropped the oil at 500 miles for good measure. A new clutch needs a few miles before it can be hammered on. Also note that as a clutch breaks in, it tends to shed excess material. By changing the oil at 500 miles you're clearing the motor of the expelled clutch particles. This practice of keeping the oil free of debris will go a long way in preserving your motor.
After the brief break-in procedure the R1 was back to its old self. Clutch take-up was as smooth as stock and lever-pull was equally easy, despite the high-performance springs. Now we can clutch a few wheelies and whack the throttle without fear of a slipping clutch, and it only took us 45 minutes from start to finish.
If you've got the clutch-slipping blues from ham-fisted riding techniques, forget factory replacements, try a Kevlar kit from KG.
After draining the oil and...
After draining the oil and removing the clutch cover it's time to ditch the wasted factory plates and discs.
Fill the clutch basket with...
Fill the clutch basket with the KG parts and button it back up. Don't forget you need to take it easy on the new clutch for a few miles before letting the throttle fly.