Bear with me on this, I know it has been done to death over the years but I have a new twist on this one, well new to me anyway. The temperature had risen to +10C in the garage (well it is S. Devon) so I thought I might go in there and try the old 'add a friction plate in first' ruse. The bike's on SORN anyhow and a man has to get his Ducati fix somehow. First I fitted a new 2.5mm thk aluminium plate in first, deleting the next plain steel plate and then the rest of the pack as normal - Clearly the pack was too tight. You could feel the drag when the clutch lever was pulled in with the bike in gear and turning the rear wheel by hand. So out it all came since this was obviously going to cause crunching gears and difficulty finding neutral with the engine running. I'd heard that some people find this clutch drag when they do this mod. Thinking about it I wondered why it works for some but others get clutch drag so I tried an alternative clutch plate which is steel but only 2mm thk and the rest of the pack as before. Lo and behold the clutch drag had gone so I started up the bike - clutch clank has virtually gone and it changes gear Ok and neutral is just as easy to find as before. OK technocrats! How come the 2.5mm aluminium plate didn't work but the 2mm steel one did????
LOL :biggrin: But seriously folks its down to how much lift you get from the pushrod and the total thickness of the clutch stack, plus how much the springs on the face plate compress which determines the clearance and hence how easily or not the action of the gearbox is.
Ambient air temperature causing dissimilar metals to expand/contract at different rates. sounds almost plausible :biggrin:
As we are talking 0.5mm in pack thickness difference I think I would be a little apprehensive the first time out. After all, it's all going to get a lot hotter which causes expansion... Just a thought
Been thinkin this thru and as i see it, in the stock setup, you have two planes of very low friction. The two steel plates at the back of the pack, and the plain steel plate up against the pressure plate. When the clutch is disengaged, these break pretty easily and the clutch pack spins with little drag. Putting a friction plate at the back of the pack, locking it into the drum, creates a plane of much higher friction against the first steel plate and makes for a higher risk of drag. As the pressure plate is the moveable part of the clutch, it tends be this area of the pack that frees off first. The inner area is less affected and if this is where the extra drag is being created......... Take a look at the wear in the basket or on the friction plate tangs. There tends to be more wear towards the outside of the clutch than inwards. This is where the plates are hitting the drum on take up. The ones at the back are already in contact with the basket..taking up drive but not really transmitting any torque. If you're running an upgraded slave which reduces clutch throw or the pack is towards the thicker end of assembly, then you'll get drag easier and the problems you get along with that. Also, friction material will have a bearing. Organic tends to be a bit softer and more progressive on take up but seems to drag easier. Sintered is harder, and is more abrupt in take up but tends to drag less....it's more on/off in its engagement. Clutches with sintered plates seem to rattle more as they disengage more readily...and why they usually feature in slipper clutches. I'm going for a sit down now.............
Nelly, you could be onto it. The 2mm thk steel friction plate I put at the back was a worn sintered plate, i.e. less friction than the new organic 2.5mm thk alum. friction plate I tried first.
I have also reduced any residual main clutch brg. end load created by contact of the inner friction plate lugs with the curved inner end of the basket's slots from 107.6kgf to 74.5kgf, around a 30% reduction, by increasing the washers under the spring collars. There hasn't been any reported noticeable brg. wear by others with this mod. to my knowledge but if it runs well with less end load then this is a plus and my mileage/annum is in the hundreds and not thousands anyway. Another option is to lower it less to 92kgf (-15%), but a road test is needed to check this.
