Clutch Replacement

[dialedn07]

My overall question in this thread: Is there any tell tale signs of when you need to replace the clutch. Details follow.

Please forgive my "technical wording" (noob)

This past weekend at Barber, the last two and a half sessions of Saturday I was having problems. My engine kept slipping from 13k rpm's and up. Low and mid range was fine, but once I reached upper rpm's no power was being put down to the wheel and the tach would slip all the way up to redline. Obviously, I ended up short shifting, but this happened on a regular basis. After some small tweaks to the clutch lever, I had the same problem on the first two sessions of Sunday. After talking with Derek in the parts trailer we made some more adjustments and there were no more problems.
With the abuse my clutch took, I must have been prematurely wearing it out. What do I need to be looking for in regards to a clutch wearing out. I ride the bike hard on the track and overall it has 9k miles on it street and track.

Thanks for the input

[riddler]

+1 on the request for info on this issue. I had a similar problem on my last day at Putnam this year. I have 20K on street and track on my 98 R1. I also dealt with it through short shifting.

A friend suggested that it may not be wear on the clutch plates, but the compression springs fatiguing. He also said there are performance spring kits that may solve this problem.

I haven't dealt with this before, and haven't started my off season investigation. Any help is appreciated.

Also, not to confuse this with the more violent feeling of a transmission slip caused by worn dogs on the gears in the trans. I had that problem as well, but corrected it a few years back by getting them undercut.

[Steve]

OK, I'm not an expert on this, but if your clutch is properly adjusted and it's slipping, that is the "tell tale sign" that something is wrong. In the service manual for my honda there are specifications on how long the springs should be and I don't remember if you put all the plates together and measure that thickness or measure individual plates, but if it's not the springs, it should be the plates. There are 2 types of plates, friction and steel. You want to make sure the steels are not warped by stacking them up and looking for gaps. Another check for the steels is, are there any marks on them. I usually just replace all the friction plates and am good to go.

HTH, and is somewhat correct,
Steve

[physicistkev]

In general, once the miles get up there you will start to see the clutch start to slip as the power of the bike really comes on. Obviously it will start to slip where the bike is trying to pull the hardest. Typically high in the RPM range. What you are describing (dialedn07) sounds like clutch slip. This may or may not be due to a "worn" clutch. It could be due to improper clutch lever adjustment, as it appears to be since you changed the lever adjuster and the slip went away. As the clutch wears you will have to continue to adjust the clutch lever and as you get close to the end of adjustment it's time to start thinking about replacing it. This and clutch slip are the only real things to look for.

Most bikes use a wet multi-plate clutch system. This consists of 2 types of plates. Drive (friction plates) and driven (steel plates). The drive plates are connected to the rotation of the crankshaft and the driven plates are connected to the rotation of the transmission. These plates are stacked, in an alternating fashion, inside the clutch basket. When you pull the clutch lever in you are "spreading" the plates apart and letting them rotate freely in comparison to each other but in sync with the crankshaft (drive plates) and transmission (driven plates). The clutch is simply how you separate the overall drive train into 2 pieces, disconnecting the engine from the rear wheel.

The plates have different wear characteristics. The drive(friction) plates are usually made of some sacrificial substance (carbon, metallic, kevlar....) and usually look like circular brake pads, only thinner. The driven (steel) plates are thicker and just steel or some steel alloy. The drive plates wear thin, similar to brake pads and the steel plates tend to warp. These are the 2 reasons the different types of plates go bad and cause clutch issues.

If you want to inspect your clutch its rather simple to do. Just pull the clutch cover off and remove the spring mechanism to get access to the plate stack. It's a bit more complex but in essence, that is all your doing. Most manuals will have a "stack thickness" measurement or even a measurement of the individual plates thickness as a tolerance. I will use my manual as an example. To measure the stack thickness you take all the plates out and stack them up. You place 5#'s of pressure on the stack and measure the thickness. If it's in a certain range then it's still good. If it's not, you have a few options on what to do. You can check each individual drive (friction) plated thickness and discard any that don't meat the criteria described in your manual or you can buy a set of drive (friction) plates. To check driven (steel) plates you don't measure thickness, you just check to see if they are flat. Lay them on a piece of glass and press around the edge, if it rocks, it's no good and should be replaced.

I have found for my bike that it's easier to buy either the whole stack, drive and driven plates as one piece or just a set of drive (friction) plates if all my steel plates are good. Once I have to replace half of both types of plates it's about the same cost as buying them all as a set. Replacing is as simple as removing the old stack and installing the new one(make sure to soak your new drive (friction) plates in oil for at least 24 hours prior to installation). Obviously, follow your manual and you can't go wrong. Not sure how the newer bikes are but I would assume it's not very difficult to do. My only other suggestions are this. Make sure you replace any gaskets you may remove when you are opening up the motor. Use stock plates, both drive and driven. I have yet to find aftermarket plates that work better than stock. Do an oil change at the same time. I have the ability to change my clutch track side, in 20 minutes, but I don't recommend it.

[physicistkev]

Springs are a whole different issue. Much simpler though. Just pull the springs and measure their uncompressed length. Your manual will have the length and tolerances required. stiffer springs are good if you have constant problems with getting hp to the rear wheel. They are also HELL on you left forearm at the track so be weary about getting them.

My bike uses a diaphragm spring rather than 4 or 5 coil springs. I have found a happy medium with a one stock spring and one Barnett heavy duty spring. I get a bit more grab and I don't feel like I am lifting weights at the gym :).

[dialedn07]

psysicistkev
Thanks for your in-dept reply....its greatly appreciated. Thankfully the adjustments did fix the problem, now I'm only worrying about how much damage I did to the clutch itself.
Thanks for the how-to as well. Definately something I'll be looking at during the off season.
Thanks again

[physicistkev]

The worst thing you did was accelerate the removal of material from the drive plates and/or warp driven plates. The removal of materiel from the drive plates is not much of a concern but warping of driven plates is much more likely with clutch slippage.

[physicistkev]

One thing I forgot. Don't be fooled by other things that feel like clutch slippage but aren't. Spinning the rear wheel and moving from the center of the rear tire to the edge and back.

Spinning the rear tire is fairly obvious but the other is not. For example, at VIR North on the straight you will notice that as you lean the bike over at the tree you move from the center of the tire to the edge of the tire. You will see and hear a marked rise in engine RPM. This is due to the smaller circumference of the tire at the edge versus the center. When you start to straighten the bike back up you go back to the center of the tire and you see and hear the engine RPM's come back down. Sounds and feels like a clutch slipping. I also see this at Summit Main going through turn 2.

[Goose]

Check the bracket that holds the clutch cable going into the case. I thought mine was due for a replacement as well when I started to take the cover off I noticed that the spring that is on the outside of the case was sheared, although it looked like it was in one piece.

[Handicapped Racer]

yank your clutch pack, I'm willing to bet the steels are black an blue, possibly warped.
if a clutch is installed properly, the only reason to adjust it would be to set the feel of engagement to your liking.
You can adjust the cable to give you a instant feel "as soon as you grab the lever it's firm", but what you may wind up doing, is causing pre mature disengagement. So as the clutch starts to wear, there isn't sufficient pressure to transfer full power to the output shaft, thus you get high rpms and bikie go no where lol!

Most of the time it comes from people adjusting the clutch lever and cable improperly. A side effect or worry with a imporperly adjusted clutch is debris from the clutch plates sticking to the inner/outter hub of the clutch basket, and or debris settling in the nooks and crannies of the cases, also in the oil pan. The biggest thing i see on drag bikes, is excessive clutch material in the pick up and oil pan, from multiple launches. That is in essence, what you've done, while at barber. Better to be safe than sorry.

Clutch plates do not need to be soaked in oil for 24 hr, 10-20min or as your preparing to peform the repair you can drop them in a clean pan, fill it with 1 qt of oil, better yet the oil your are going to use for the oil change someone suggest you do in conjunction with the clutch change.

[Handicapped Racer]

Check the bracket that holds the clutch cable going into the case. I thought mine was due for a replacement as well when I started to take the cover off I noticed that the spring that is on the outside of the case was sheared, although it looked like it was in one piece.

The spring you speak of isn't strong enough to interfere with engagement or disengagement of the clutch, it's just meant to keep tension on the calble so the lever doesn't rattle around. Good eyes on your part though!

[physicistkev]

I remember seeing issues with clutches on a big bore bike (GSXR or R1) that was fixed with a long oil soak? I have done mine dry without issue, but a longer soak can't hurt. :dunno: Just stay abreast of any known issues with your particular bike and follow what your manual says. You can't go wrong there.

[Handicapped Racer]

Just stay abreast of any known issues with your particular bike and follow what your manual says. You can't go wrong there.


You are very correct, and nice write up, if i must say so myself, very detailed.:adore:

[physicistkev]

Thanks T

If only i could ride like i explain things...
:doh: