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Torben
06-14-2004, 12:19 PM
I used to be able to two-finger my clutch. Now, with my thick gloves on I can't two-finger it anymore cuz the gloves are too thick and the clutch isn't engaging fully with my other fingers in the way. I recently tried it with my thin gloves on, and for some reason, I need to pull the lever in all the way to the grip to get it to engage correctly.
How can I adjust where on the clutch lever travel the clutch is actually engaged? Is it a cable stretch issue? How is that corrected?
2004 749 Dark
Thanks for your wisdom.

darkduc
06-14-2004, 12:51 PM
Umm, dude, it's hydraulic. No cables. :)

Torben
06-14-2004, 12:53 PM
:rolleyes: ok fine
so now what?
more fluid?
change fluid?
longer plunger?
deal with it?

darkduc
06-14-2004, 02:01 PM
Good question... dunno. (some help I am)

I'd like to know as well.

Torben
06-14-2004, 02:11 PM
Yeah thanks :rolleyes:
You're fired! :D

I honestly think there may be air in it and needs to be bled. The fluid level is fine.

darkduc
06-14-2004, 07:02 PM
Hey! I just got the job! Don't fire me yet! :D

Ok, so, it doesn't talk about 'adjusting' a hydraulic clutch but this article (http://www.ducati.net/faq.cfm?id=47) I poached off of ducati.net is enlightening.

Here's most of it, copied here for your convienence. (It's lots of work to click the link, I know.)

I think I'm hard on my clutch :( I might need to replace it pretty soon, based on the descriptions in this article.

My clutch engages pretty far out on the lever's action which I would guess to mean that the 'clutch stack' is getting worn down. Guess I'll need that shiny red job like you have T?! :D

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Clutch Tuning Voodoo
submitted by Larry Kelly
Clutch Tuning Voodoo

Clutch engagement problems are quite common, but solving them often requires a fair amount of trial-and error work.

Usually, an uneven take-up or excessive slipping signals signals the need for a clutch pack replacement, often just caused by normal wear loss of the friction material on the plates. The mileage between replacements has a very wide range, anywhere between 3,000 and 30,000 miles, depending upon the amount of city riding and the rider’s launch style. If the clutch type is a slipper, it’s normal for the friction material to wear-out sooner since it’s function is to allow the plates to slip past each other under high engine-braking loads during downshifts. Some friction materials do better than others regarding wear and engagement smoothness, just like brake pads.

Sometimes engagement problems begin after you’ve just replaced your worn-out stock clutch components, upgraded to an aftermarket clutch or changed to a slipper clutch.

The key to smooth engagement is controlling the frictional force developed between the smooth plates (that are driven by the engine clutch hub) and the plates that contain friction material (that drive the rear wheel through the clutch basket.)

The amount of force developed between these plates is controlled by the stiffness of the clutch springs, specifically by the amount of preload on these springs. When the clutch is fully engaged, the friction force developed between the plates needs to be greater than the engine’s applied torque to prevent slip. About 430 lbs is needed on a stock superbike.

When you pull-in the clutch lever, the hydraulic pressure applied to the slave cylinder overcomes the spring’s preload and progressively reduces the force pushing the plates together until they begin to slip. During this time the dished plate(s) in the stack act to provide a progressive reduction in the inter-plate force as the plates separate a few millimeters and you get full disengagement.

When you engage the clutch the opposite occurs. The reduced hydraulic pressure on the slave cylinder allows the push-rod to move the spring-loaded pressure plate toward the plate stack (a millimeter or so) until the plates begin to touch. Keep in mind that when you move the lever you are changing the POSITION of the pressure plate. You have only indirect control over the forces between plates.

The forces between plates is controlled during this transition (between disengaged and fully engaged) by a dished plate that is included in the stack to smooth this transition. This plate acts as a spring (pushes back with a force) when it gets flattened between adjacent plates by the movement of the pressure plate.

So, the force pushing the plates together first come from the smaller force produced by flattening the dished spring plate, and later, a much greater force produced by the preloaded clutch springs.

The higher the height of the clutch pack, the greater the clutch spring preload. So, as the clutch pack friction material wears-out, the pack height gets shorter, until the force between plates is insufficient and the clutch slips, at first under high torque conditions such as at launch, and later even when the lever is not pulled at speed. Time for a new clutch.

This is also the cause of the annoying phenomena of clutch “judder” such that when you release the lever, and while the spring plate is being compressed, the clutch springs can’t develop a sufficient force to prevent slipping so the plates slip, grab for an instant (causing vibration-induced slip,) grab, slip and so on, until the slipping stops as the engine torque is reduced when the bike acceleration eventually drops-off.

Here’s the Physics behind it. The friction force developed between two surfaces depends on whether the surfaces are sliding past each other or not. For a given amount of force pushing any two surfaces together, less frictional force will develop between sliding surfaces, than between surfaces that don’t. Once surfaces are together it takes more force to get them to slide than to keep them sliding. One they begin to side, however, they’ll keep sliding unless you push them together harder.

It’s these alternating higher-lower friction forces that cause the vibration that you perceive as judder. Sometimes adding a second spring plate to the pack will help to damp-out certain vibrations, so Ducati specifies a different number of flat plates, dished plates, plate thickness and stacking sequence for different models. The common spec however is stack height. Ducati clutch packs are stacked to 38mm ± 2mm.

<snip!>

See the rest of the article (http://www.ducati.net/faq.cfm?id=47) with examples.

darkduc
06-14-2004, 07:23 PM
Here's another post from some forum somewhere....

I had to use google's archive service to resurrect it (http://216.239.41.104/search?q=cache:5dVe0J8fTToJ:www.totalbikebits.com/forum/showthread.php%3Fthreadid%3D346+adjust+ducati+hydr aulic+clutch&hl=en)..

This is in regard to a Kawasaki but should pertain to any hydraulic clutch...

Hi Ton-up!

I know your posting about adjusting hydraulic clutches was a long time ago, but I couldn't see that anyone had actually answered your question! So in case you're still wondering, here goes!

The answer is, you don't! Hydraulic clutches are by their nature self adjusting. That is, the piston in the slave cylinder has a spring behind it which pushes the piston out until it is in contact with the end of the clutch push rod and all the clearance is taken up. Assuming the system has been properly bled (in tne same way as you would bleed your brakes) as soon as you start to pull in the lever, the clutch should start to lift. There may be a very small amount of travel before this happens because there is a small expansion hole in the master cylinder which has to be covered before pressure can be transmitted. The only adjustment available on most machines fitted with a hydraulic clutch is for reach on the lever. If you want to ensure that you are getting the maximum amount of lift possible, then set the reach adjuster to maximum, i.e. the lever is furthest from the handlebar. This should minimise drag too. If your system hasn't been bled through for a while, degradation of the fluid can also result in poor operation. Just bleed some fresh fluid through until you can see clean, new fluid in the bleed tube and all the old dirty stuff is flushed out.

All the best, hope this helps!

Pete C.

Torben
06-15-2004, 12:09 PM
OK so it's self adjusting and if it don't work it needs a new clutch pack.
So, I did some experimenting this morning. Seems if I pump the clutch lever maybe 30 times, the pressure gets back to where it should be.
It will then drop pressure and go sloppy again over time as the bike runs.
So maybe I have air in my lines and I need to bleed the system?

darkduc
06-15-2004, 12:14 PM
Sounds reasonable.

Robb
06-15-2004, 12:31 PM
For what it's worth, my clutch is fully engaged after pulling it in about 1/4 of the way. I also planned on adjusting the lever closer to the handle so I didn't have to reach so far for it and because it doesn't need to be pulled in very far to completely engage.

Torben - I can't imagine after the few miles you have on your bike that you need a new clutch pack. Of course, I haven't ridden with you yet either. So I'm not sure why you'd need to pull the clutch all the way in to engage - you may be on to something with a fluid bleed. I had a similar problem with hydros on an old mountain bike and a bleed fixed the problem.

CINDESMO
06-15-2004, 01:33 PM
There is a little adjustment screw on the lever that you might try. From what I have seen, it seems to take most riders from 4500 to 8000 miles to wear out a clutch pack on the dry clutch system. When your clutch pack is worn it will be so loud (with a vented clutch cover) that you will forget all about the loud exhaust. When you are at the shop Saturday, one of the service techs can give you advice.

Torben
06-17-2004, 12:01 AM
Indeed a blood letting was in order. I was able to get the scoot in to duc sea and have those pesky air bubbles removed. Works like a champ now. I guess a closed system still has holes in it somewhere.

darkduc
06-17-2004, 05:42 AM
Hey, cool! Glad to hear that did the trick.