slipper clutch

well which one are we talking about here kz-mtd?

we were talking slipper and I got side tracked with 1395:silly:racerZ commit.

Post edited by: kz-mtd, at: 2006/01/01 11:06

Actually reading the comments about motor size.Yes a 1200 with a good head will get the job done but won't have the torque and midrange of the 1395. The same head on the 1395 will bury the 1200 at the same weight. Had lots of experience with both.

Way back some people referred to lock ups as slippers and the very first lock ups from Denco did have a primitive device/adjustment to allow some slip on the Dencoglide. Nobody could run a slider on the street, what are you going to have a two step button to leave on the green?

Post edited by: jack, at: 2006/01/01 20:03

Guess we need a Dictionary to define the terms, or be real specific in describing the part

Click on the gszone I linked above, and APE has both a slipper and a centrifugal lock up clutch listed (as they define the terms anyway).

Maybe we should create a dictionary of motorcyle terms and post it as an article or in the filebase, then we could all use the same terms and maybe understand what others say

I have traveled a bit, and lived in a number of different places, and I have run into this many times, different places have different meanings attached to the same words.

Quick explanation.

Factory "slipper" clutch has been described above eliminates wheel lock up on down shifts.

Slipper / slider as it applies to KZ Kawasakis. This clutch operates just like the clutch on a mini bike or go Kart. There is no clutch lever. Bike sits still at idle, open the throttle and as RPM increases, weighted arms in the clutch extend and force the pressure plate against the clutch plates and the bike moves. The RPM at which it moves the bike is called "stall". This stall can be adjusted by adding or subtracting weights in the clutch. One can get the stall set to right in the strong part of the torque curve, making the bike leave very hard.

The advantage of this kind of clutch in a drag bike is consistency. It leaves exactly the same every time.

Lock up clutch is something like the slider in that it also uses weighted levers. But in this case, the assembly is bolted to the pressure plate and only turns as the rear wheel turns, not RPM. As the rear wheel turns faster, so does the inner clutch hub that drives the lockup mechanism and the levers move pressing the pressure plate tighter and tighter. Finally at high speed the pressure plate has locked the clutch pack up much tighter than and heavy duty clutch springs could.

So in a nutshell, both mechanically lock up the clutch. Slider / slipper according to engine RPM, Lockup according to vehicle speed.

You can see both types here;
kzzone.com/clutches.html

Jay

Post edited by: APE Jay, at: 2006/01/02 00:28

slipper clutches prevent wheel hop, and provide smoother corner entry by not upsetting the chassis (pitch) while trying to match revs on high comp. engines especially on twins, making one less thing you have to concentrate on while pitching the bike over, trail braking and grabbin downshifts. These are a staple in the roadracing communities and at the higher levels of competition you will easily drop seconds off your lap times with this installation. The second benefit is the unsprung weight off your engine, I shaved 6lbs off my Ducati clutch with just an intermediate level full billet slipper with an alum clutch pack. There are 2 types...ramp and ball or diaphram, both with pros and cons but ramp and ball seems more popular. This isn't for someone who doesn't know how to use a clutch...I hope that guy was kiddin' but for someone who can actually ride at a level to obtain the benefits of a slipper clutch. I'm an intermediate level former CCS racer and now occasional track day guy and I highly recommend them to anyone who takes it to the track or strafes the local canyons. Finally the manuf. are stepping up and starting to include them on the high performance bikes but even those are rather choppy and not on par with aftermarket quality aluminum adjustable unit. better than nothing.

KawasakiJockey wrote:

Wheel hop and sidestepping are 2 reasons. The most important reason is to minimize grenading the engine because of over-rev at downshift. I wish my 954 had one as it takes a lot of concentration to grab front brake, downshift, and slip the clutch so the back tire doesnt come around on me.

If you're talking about downshifting to a stop, you can pull the clutch, rev the engine to a higher RPM (whatever is appropriate for a lower gear), and let the clutch out more quickly. This is how I usually wind down during gentle stops with nobody behind me (no brake = no brake light).

The technique definitely helps when you've got to throw in some brake for a more energetic stop. It takes a little practice, but when you can match engine RPM during a downshift your clutch technique isn't quite so critical.

No, that is not what I'm talking about. I'm talking about running your bike at the limit at a roadracing course. This is running the bike at the top of the rev band and taking a turn that is 1 or 2 gears lower. So if you are at the rev limiter in 4th gear at 150mph and get on the brakes and downshift at the brake marker while starting to tip it in on a 115 mph turn, you want the engine and rear wheel coupled before you are at full lean or you will definately high-side.

Post edited by: kawasakijockey, at: 2006/01/02 11:23

Post edited by: kawasakijockey, at: 2006/01/08 10:10

To do that you need to learn how to feel the engine with the clutch. You then balance the road speed with the brakes til you feel the match.

It's getting obvious that unless you've had even a minimal amount of roadracing experience this is going over alot of peoples heads...

Some bikes have more engine braking effect than do others. If you downshift hard while engine braking as well, the back end can break loose. This isn't JUST road racing but it also happens on the street. Many of this year's sport bikes are putting slipper clutches (not slider) into sport bikes so the owners will have more margin of error when they hit a corner to hot. The WORST bike I have ever owned for breaking the back end loose on a hard downshift was a Venture. It made you look silly and was scary! The Kawasaki Vulcan family of bikes has LONG put a round disk with teeth called a clutch spring in their clutches that acts as a poor man's slipper clutch to reduce the amount of wheel grab that causes a rear end to break loose on a hard downshift. Go to buykawaski.com and look at one of the exploded diagrams for a VN1500 clutch basket assembly.

BTW: I have had a motorcycle license for over 40 years now and know how to ride. If the folks who are telling other folks to learn how to ride and use a clutch have ever ridden a 180 hp bike FAST on a road racer course OR hard on the street, they would be more gentle about this stuff as those darn bikes are so powerful and fast, even the best riders in the world use slipper clutches. There just isn't any margin for error on the new sport bikes with their great performance. As far as drag racing... the fast guys use more gizmos to help them shave time and I bet the ones that are winning don't feel embarassed about using those gizmos including a slipper clutch.

Post edited by: wiredgeorge, at: 2006/01/06 16:18

Didn't take me long after getting my license(1982)and my KZ650 to start locking up the rear tyre going hot into corners. Started paying attention to road racers on TV and noticed them downshifting and giving engine some revs at same time. Older car trannies without synchromesh had to be revved before letting out clutch to get engine speed and rear wheel speed to match. Try cranking your idle speed up to about 5000 rpm and the rear wheel hop will go away to some extent. Not practical for street but does work at some tracks. As long as you don't go below 5000rpm in slow corners.