Clutch adjustment behaving strangely

[themoudie]

Colin, George and Eldert,

Thank you all for your comments. I too appreciate the modification to the clutch pressure plate Eldert. But having taken measurements of the lift of the centre of the clutch adjusting screw, I am using my original '74 450 pressure plate and only achieving 1.5mm of lift at the adjusting screw and the same between the spring cups. Consequently, the clutch is dragging.

If I try to adjust the clutch adjusting screws head height above the pressure plate, at present, I cannot screw it in further than 7mm, so I am not able to achieve the factory recommended 5mm height above the prussure plate, because the clutch accentuating arm is pressed hard against the gearchange inner case.

However, I think that the problem lies in my assembly of the clutch. Having converted from 1mm steel plates to 2mm steel plates, I also purchased new friction plates, springs (22Kg), spring cups (pressed steel), pushrod set, fitted with new washers and allan screws.

I will have to dismantle the clutch tomorrow and take a closer look as to "Why?" I cannot achieve sufficient lift to free the clutch. I have a nasty suspicion that I have 7 x 3mm friction plates installed and 5 x 2mm steel plates, plus the 1mm spacer between the back of the clutch huib and the clutch basket. Whereas I should have only 6 x 3mm friction plates and 5 x 2mm steel plates, plus the 1mm spacer between the back of the clutch huib and the clutch basket.

This would also create a stiff clutch, because the springs are already pre-loaded, with the extra 3mm plate in the clutch stack.

Talk about feeling a "42 carat plonker"! However, if this helps others and this is the problem, I'll no be too embarrassed.

Good health, Bill

[Jordan]

Do you have an original type handlebar clutch lever, or something with different geometry? That is, distance from fulcrum to cable nipple.

[graeme]

Hello Bill,

My 450’s all have light clutch pull.
If I try and hide the cable, they are too hard.
All have 450 springs and standard clutch levers.

Regards
Graeme

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[Eldert]

Hi Bill

another option would be reducing the stack height by removing the friction material of the first plate
in the basket .

Eldert

[themoudie]

UPDATE

Thank you Jordan, Graeme and Eldert for your suggestions.

Jordan, the distance from the fulcrum to the centre of the cable nipple on the 'Tomaselli Matador" clutch lever that I have fitted is 30.0mm.

Graeme, I see that you almost "drape" the cable around the cylinder. Mine comes out to the left in an arc and is then routed above the centre of cylinder head, below the frame top tube, over the top of the right-hand tank mount, between the steering head and right-hand fork stanchion and thence to the clutch lever. Once I have re-assembled the clutch, I will try your route and see if it makes an improvement.

I have stripped the whole clutch out and removed both the hub and basket from the gearbox input (mainshaft) and found that I have the original spacer (5.4mm depth) between the input shaft bearing and the clutch basket casting. The two bearings supporting the clutch basket are snug and within the depth of the basket's hub casting. I had placed the additional 1mm depth spacer between the clutch basket bearing and the inner face of the clutch hub, thereby extending the depth between the front of the hub and the clutch basket friction surface by 1mm. There are 6 x 3mm 'Surflex' friction plates and 5 x 2mm steel plates installed onto the clutch hub (Depth from front of clutch hub to the inner friction surface of the clutch basket is 32.8mm) and held in place with the original Ducati pressure plate that has a friction surface plate 2.5mm in depth (Overall depth of the pressure plate is 11.0mm between faces). The depth from the outer face of the clutch basket tangs to the basket's inner friction surface is 29.5mm. The springs are new 22Kg springs, with a length of 26.5mm and the length of the spring pillars in the clutch hub are 29.0mm.

This where my brain starts to hurt; but I think that the clutch basket is over-stuffed with plate thickness! The sum of the friction plates+steel plates+pressure plate, friction plate of 30.5mm and if the total depth of the pressure plate is used, 39.0mm.

So, specifically, how do I calculate this rather than having a hunch?

Before dismantling to see if I had assembled the clutch in the correct order, I tried to achieve the 5mm depth between the top of the clutch adjusting screw and the pressure plate recommended in the Clymer manual and couldn't! The best that I could achieve and still retain 2mm clearance between the accentuating arm and the gearchange mechanism inner casing was 7.0mm. The push rod set is new and has an overall length of 213mm and the adjusting screw, original to this engine, has an overall length of 39.6mm. I have no idea as to how much lift I should be measuring, to ensure that the stack frees itself, rather than dragging?

Eldert, if I were to strip friction material from either one or two faces of a friction plate, where in the clutch stack should I replace it? Alternatively, could I retain the 6 friction plates entirely and replace one or more of the 2mm steel plates, with 1mm steel plates that I have. This would retain the friction area, yet reduce the congestion in the stack, but possibly allow clutch slip?

When I stripped the clutch there were deposits of dark brown friction material adhereing to the hub and the half moon tangs of the steel plates. Not excessively, but sufficient to note. All the components have now been cleaned in brake cleaner.

Thank you for your time and suggestions.

Good health, Bill

[mrkprsn]

What is the correct height of the clutch stack? I seem to remember years ago I had a similar problem when I changed from thinner clutch plates to thicker ones. I was over the 27MM spec height. I forget by how much? I think I swapped out a couple of the ticker plates with thinner plates and the height ended being 26.5MM. That did the trick. Easier action and no slippage. I think your feeling of having an over stuffed clutch might be correct.

[George]

Standard new clutch set: 7 x 3mm friction plates 6 x 1mm plain plates = 27mm
Nigel's uprated clutch set: 6 x 3mm friction plates 5 x 2mm plain plates = 28mm
Not sure about 1mm spacer check with Nigel, I believe this was added to early uprated clutch sets and then discarded.
As suggested in previous post why not try changing one or two plain plates to get within 27mm maximum spec.
As far as I know the only difference between 350 and 450 clutch is spring compression rate.
Good luck

[ranton_rambler]

I know my bike is only a 175 but when I first built it the clutch was a 2-handed pull, but I also noticed that the stack height was more than the height of the centre hub. That bit was a replacement I got somewhere as the original was badly ridged, so probably the wrong one. Anyway, I took one pair of plates out and it’s been fine ever since. Not too heavy and no slip, although I think the clutch is oversized for a 175 as it’s also used on the 250?

[themoudie]

Thank you mrkprsn, George and ranton rambler for your thoughts.

mrkprsn, stack height should be 27mm, but the thicker steel plates take it to 28mm, hence the use of the 1mm spacer between the hub and the basket, so as to maintain the ability of the springs not to become coil bound, when disengaging the clutch and allow complete plate separation.

George, Nigel supplies the 1mm spacer as a matter of course, in his kits that include the 2mm steel plates. I have emailed Nigel directly, pointing him to this thread and asking for some guidance, when he has the opportunity. I agree that the only difference between the 250, 350 and 450 widecase clutches are the spring resistance and dimensions. The 250 and 350 using the 17Kg springs that appear longer and made from a different guage wire from the 450's 22Kg springs that are 26.5mm in length.

ranton_rambler, that 175 clutch is essentialy what I have in the 450. It may be oversized for the 175, but on the 450 it has always been an Achilles heel, especially when used in town traffic, or the engine is given a tuning that increases the torque. The 1mm steel plates warp and I have also warped a brand new Surflex pressure plate that only had the 1mm friction plate fitted. I have had to revert to my well worn original pressure plate, with its 2.5mm friction plate and heavier guage pressing retaining the spring cups. Eldert mentioned this in his posting in this thread and I had already found top my cost by experience. I do not think that the Surflex 2.5mm pressure is still available, BUT, I may be wrong!

Good health, Bill

[Duccout]

Hi Bill,

There is an answer (at a price). Carlo Leoncini (motofficinialeoncini.it) sells an aluminium pressure plate, along with an accompanying clutch centre, which looks like it will solve any problems. Maybe a Christmas present?

Cheers,

Colin