SBK clutch issues?

[duc_748]

Can anyone shed some light on why my 02 748 will not go into neutral while the bike is running? Last track day I found it impossible to put the bike into neutral unless I turned off the engine, then it engaged effortlessly, does that make sense to anyone? I put a 999R clutch basket and plates into my 748 a few years ago and it has worked fine up until recently. I bled the clutch right before my last track day and it made no difference at all. I have been told it might be "dog ear gear" or something along those lines, if anyone can shed some light on what that even is that would be great. The bike starts in neutral and runs fine, but once you put into gear it just will not go back into neutral until you turn off the ignition....strange right? Any insight would be great...thanks

[Shazaam]

Difficulty in selecting neutral is the result of the clutch plates still dragging after the cluch lever is pulled in. As the plate friction material wears, the plate stack height gets reduced so the problem usually becomes less severe over time. If you've recently replaced the clutch plates, the stack height may be too high, which will also cause the problem.

Two possible solutions:

Your 4-position clutch lever adjuster is placing the lever too close to the handlebar so you're not getting complete separation of the plates. Try a different adjuster position that gives a longer lever stroke.

If you are still unable to engage neutral, the most likely cause is air in the clutch hydraulic line. A trapped air bubble can compress (the fluid can't) so you won’t get a full stroke of the clutch pushrod and the clutch doesn’t fully disengage.

Air bubbles rise to the highest point in a hydraulic system so that's where bleed nipples belong and are usually placed. In Ducati superbikes the bleed nipple is placed at the lowest point in the system (duh) so the only way you can bleed all the air out is for the bubbles to be carried along with the fluid as you bleed, and bleed, and bleed the system. It is possible to bleed the system without using a bleed nipple at the master cylinder, but sometimes it takes a lot more attempts.

So, the Ducati clutch line is notoriously difficult to bleed using just the nipple at the clutch slave cylinder. Evoluzione and Yoyodyne, two aftermarket manufacturers of slave cylinders, often encountered customer bleeding problem related complaints so began selling a banjo fitting having a bleed nipple for use at the highest point in the hydraulic system. It works.

Here’s what it looks like:



Another common reason that the clutch won't completely disengage is that the aftermarket force-reduction slave units (and later model Ducati slave units) move the clutch pushrod less distance - a design trade-off to accomplish a reduction in clutch lever forces.

Is your slave cylinder an aftermarket unit?

[duc_748]

Shazaam, As your screen name suggests, you got the super hero powers and insights! Thank you! I have a the stock clutch lever and master on my 748, I did but a GP radial brake lever/master on, but the left the clutch OEM. The clutch slave cyl. is a aftermarket, Evoluzione model, I installed it sometime last year. Well it sounds like I either need to pull the clutch plates apart and check stack height, or really bleed the lines(that is not from the bottom bleed screw on clutch slave). Thank you very much for the help, I will see what I can figure out as to the definitive cause... First 2008 track coming up in March!

[tye1138]

Well, my question is; can you change gears properly? If you bypass neutral all together, are the rest of the gears easy to find and not hard to get into? If you've got a worn clutch, it will slip more then grip.

The test I always ask people to do is quite simple. Put the bike on a rear stand, put the bike in neutral and start her up. Using you rear wheel spinning speed as a gauge, you can determine very quickly if something is wrong. If the rear wheel spins out of control (if you can't stop it with your finger) whilst the bike is in neutral, or in gear and the clutch is pulled in, then you've got a plate issue or slave cylinder issue. At the same time, you can fine-tune where the clutch disengages the plates. You can change the stack and literally feel how much pull you need to get the rear wheel moving. You should be able to stop the rear wheel with one finger whilst the clutch is pulled in and the bike is in gear.Of course, you need to test it on the street when your done, but getting the proper stack is extremely simple and using the test method should help a bit with the process.

If you find that's not fixing anything, you could just have old or the wrong motor oil in the motor. The shifting quality is ALSO directly related to motor oil quality. I highly doubt you've broken something... I also agree it could be a bleeding or slave cylinder issue, but if you do a search on the forums, you'll find more info about this exact issue.