4-speed clutch mystery

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ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

4-speed clutch mystery

Postby ranton_rambler » Tue Jan 01, 2019 5:02 pm

Whilst I've got a few days off work, I've tried to progress my 175 project a bit more.
One of the jobs was making up control cables. Once I'd got the clutch cable sorted, I was a bit disturbed by the fact that I could barely pull the lever in with my left hand. I searched about on here and found a lot of earlier threads about cable routing, adjustment of the lever on the gearbox end etc, so partially stripped it to check some details. Without thinking it through properly, I decided to remove the pushrod assembly by pushing it from the right-hand side. No problem getting the 2 rod sections out, but the balls fell inside the clutch. I thought I could perhaps get the balls out by removing some of the springs and cups and sticking a little magnet in - it works too. But I could also see that the pressure plate tangs were not engaged with the drum. Once I'd got it all apart, the drum seems to be about 1.6mm short of the basket. The drum is a replacement, but is the same as the one that came out (apart from wear ridges). This is the later variant of clutch with the bearings in the basket - shown at the back of my workshop manual.
I'm beginning to suspect that the clutch is a random collection of parts. In a previous post I queried the pushrod length, as mine had 3 rod sections but no balls, but was so long that the selector cover would not assemble.
Does anyone have access to components of the same clutch so they can give me a few dimensions to check?
At present, I've put it together with one less pair of plates (i.e. 5 friction plates) and the lever now feels nice. But I suppose there is a danger it could slip as there are less friction surfaces and the spring load is reduced.
Ian
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DBDBrian
Posts: 197
Joined: Mon Mar 30, 2015 11:29 pm

Re: 4-speed clutch mystery

Postby DBDBrian » Wed Jan 02, 2019 2:51 pm

Hi Ian, measurements of late type clutch as requested.
Working from the outer face of the basket, the depth to the inner clutch plate contact face is 25 mm. The depth to the outer bearing face is 31 mm, the distance through both bearings and spacer in the basket is 28 mm. The spacer between the basket rear bearing, and the gearbox shaft bearing is 5 mm. Again from the outer face, overall depth of the centre hub, including the rear flange is 33.5 mm, the clutch plate contact depth is 30 mm. The centre hub protrudes 2.5 mm out of the basket. The early and late type pressure plates appear to be identical, apart from the centre thread and boss for the push rod adjuster, the later type having 9 mm of thread, and the early 6 mm . Both P/P centre adjusters are identical at 38 mm overall length, with 18 mm of thread.
I have both types, as to whether there are any more variations I don't know.
HTH
Brian.
Brian
Made in England

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: 4-speed clutch mystery

Postby ranton_rambler » Wed Jan 02, 2019 5:07 pm

Thanks for taking the trouble to do that Brian. I haven't pulled it back apart yet, but the basket seems to match from what I can see in my photos. The overall plate pack thickness I measured as 24.5mm, and sits just inside the basket depth.
I bought a replacement centre drum, which I don't have good photos of, but I remember putting old/new together to confirm they matched. On mine, the overall depth matches your 33.5mm, but the depth of the grooved section is only 28.25mm, so 1.75mm short. Not enough to account for the difference! Since my drum is 1.6mm inside the basket and yours sticks out 2.5mm, I am around 4mm adrift somewhere. There's no spacer between the drum and the bearing in the basket is there?
Someone has definitely been inside this clutch before as the pushrod was wrong and the outer spacer between the bearings in the basket was missing completely. New one in there now.
I did think that I can correct the spring load by packing them down by the thickness equivalent to one pair of plates, either in the bottom of the cups, or under the screw heads.
Ian

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DBDBrian
Posts: 197
Joined: Mon Mar 30, 2015 11:29 pm

Re: 4-speed clutch mystery

Postby DBDBrian » Thu Jan 03, 2019 3:52 pm

To the best of my knowledge, there is no spacer between the rear of centre hub and the basket outer bearing, as your hub measures 33.5 mm overall, and is 1,6 mm below the outer face of the basket, it would seem to indicate a variation with the basket?

Both the clutches I have are from 200 SS's , with the 175 type crankcases.
Brian
Made in England

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: 4-speed clutch mystery

Postby ranton_rambler » Thu Jan 03, 2019 7:06 pm

I've been mulling this over and I think I'll get some other bits progressed so I can ride it, and then see if the clutch slips with the 5-plate pack. It's no harder to strip the clutch on a built-up bike than in its current state as far as I can tell.

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: 4-speed clutch mystery

Postby ranton_rambler » Thu Feb 21, 2019 9:22 pm

Took the clutch apart to gain access to the generator, so I took the opportunity to measure up.
Comparing dimensions to Brian's above, the drum is different in spite of what I thought before. Overall length 30.5, grooved section 27.5. Overall approx. 3mm less, so explains why it's sitting inside the basket rather than outside.
Basket dimensions all match up.
Could perhaps fit a spacer to move it outboard a bit, but for the moment I'll put it all back as it was with 5 plates and see if it slips. Action seemed nice on my short ride at the weekend.
Ian


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