02 620 Monster, no power to wheel

[dusty]

Hey guys,

Got the bike all but done and looking pretty. Unfortunately, it doesn't drive well. or, at all.

Motor starts on the first crank, which is a first, and sounds fine though a little low on oil since I'm still figuring out the capacity with the oil cooler installed. Rear wheel (currently on a swingarm support) surges briefly when the gear is selected, but the clutch never engages properly and the wheel will eventually come to a halt even in-gear. With the motor off, spinning the rear wheel is difficult but naturally becomes easier with higher gears. However, pulling the clutch lever (tried with new levers and old, with the piston screw fully out) has no effect on the spin resistance, and as mentioned, releasing the lever does not engage the clutch.

Clutch slave was recently bled and it's a firm pressure when using the lever, but doesn't seem to do much. This is going to sound terrifying, probably, but can the clutch be actuated by hand without the slave cylinder, by pressing on the op rod (pressure required notwithstanding)? I'm wondering if the slave cylinder is shot, especially given it's the original unit.

[greenmonster]

Can you put it in gear while running?!?
W no clutch should be hard and with big noise,
don't do it. Research this w wheels on floor and engine off.

Tried w clutch lever pin fully in?
Fully out could mean not engaging properly.

[dusty]

Yeah, it'll row right through each gear without a hitch, which is part of why I think the clutch is being held open and disengaged like the slave piston isn't fully retracting. I removed the slave and ran a q tip through it, got mostly just thin gunk, but the wheel is being dragged very lightly now at least: in first gear at idle, it'll spin up to about 5 MPH, but it doesn't increase with throttle.

The lever pin was pretty far in towards the master cylinder when I first discovered this problem, but I can screw it back in and fiddle with it a bit.

This is gonna sound like a dumb question, but is the slave cylinder supposed to slide all the way up to the mating surface of the motor without resistance? I seem to need to use the bolts to pull it in towards the motor, else it gets stuck about 8-10mm away from the motor.

[ducpainter]

Your clutch is slipping.

[dusty]

I was kinda leaning towards that. Unusual, I guess, given that it has 4,246 on it.

Actually, thinking back: I picked this project up as a pile of parts, and my buddy isn't exactly the best with motors of any kind (to be fair neither am I). How long would the motor have had to been run/filled with regular car oil (+friction modifiers) to make the clutch slip?

[koko64]

Not long at all. Get that oil changed to Moto specific. Friction modified oils are the worst possible for your wet clutch bike.

[ducpainter]

In addition to changing the oil to a moto specific type, you'll need to find a way to flush the car oil from between the plates.

It might take a while of running with the clutch lever pulled for it to come around.

[Howie]

Slipping at idle and no load sounds like more than wrong oil.  Might be best to remove the clutch cover and see what is going on.

[koko64]

Pressure plate may not be seated correctly during assembly.

[dusty]

Hey guys. Got the clutch opened up, but could anyone tell me what the friction material thickness is supposed to be? I can't find jack online, except to check the service manual that I don't have.

edit:

Sorry, just found this thread with a helpful post from Speeddog:

http://www.ducatimonsterforum.org/index.php?topic=69607.0

Regular wet clutch:

Plate stack minimum height is 41.3mm.
Individual frictions 3.5mm minimum.
Springs minimum length 36.5mm (this may be a bogus number, my dodgy memory tells me I've found it nonsensical regarding springs I took out).

I'm gonna go by this for now, I think.

Edit #2:

Plate stack is 43.3mm
Friction plates are 3.45mm
Steel plates are 1.51mm
Coil length is 43.5mm

[ducpainter]

Clean the plates with a solvent, and then oil the surfaces with the correct moto oil. As Koko says, make sure the pressure plate seats all the way aginst the plates. There's an index mark on the basket and pressure polate that needs to be lined up. Tighten the springs evenly and just snug the bolts. They break easily.

Let us know.

[dusty]

Yep, definitely a slipping clutch. Pulled out all the plates, cleaned them off with isopropanol, lightly scuffed the steel plates with 600 grit (just a single pass, more out of curiousity than procedure), and put it all back together. Wheel's getting power now, but not without slippage I don't think - the speedometer didn't seem to increase linearly with RPM past a certain point. Keep in mind, this is on a swingarm stand, so it's pretty much without load.

Unfortunately, like always, two new problems have surfaced, and I think they could be related. The bike shudders frequently, both while idling in first gear and with throttle (I only went up to 3-4 thou). It's brief, but definitely there - and it goes away when the clutch is disengaged and the power is removed from the wheel. I found two friction plates in the clutch pack that had cracks through the aluminum, and while I know I'm going to replace them before taking it on the road, I'm wondering how (if at all) this could be related to the shuddering.

Speaking of, any recommendations for clutch packs? I see a lot of Barnett's, but also hear they're not great. Leaning towards OEM right now.

[Howie]

For a wet clutch i would use OEM.  Shuddering could be related to the clutch.

[ducpainter]

OEM all the way...wet, or dry.

[dusty]

Sure, I found a set on Amazon so at least it'll be here by the weekend. Worth replacing the clutch springs at the same time? They seem stiff enough, I'm just tired of making a dozen different part orders a week.