CL013 CLUTCH

I rebuilt my clutch with VOC parts and they transformed it; no slip or drag and the action is beautifully smooth. But in comparison with other Venoms I've encountered, the pressure to operate the handlebar lever is substantially greater. In short, it's smooth but heavy.
It doesn't appear to be anything to do with cable friction - I've lubed it well and re-routed it to minimise tight turns and the cable is a new VOC one. And there are no ominous noises coming from the clutch housing when I operate the clutch.
The source of the increased resistance appears to come from the springs themselves. I recall that the new springs were slightly longer than the old ones, a fact that I put down at the time to compression of the latter. VOC supplied me with C12/4 springs, so I assume that these are correct for the Venom.
All this means that although the clutch and gearbox work well, the tendons in old left wrist suffer on a longish run. I'm about to try a nylon lined cable in an effort to ease things, but do you have any other thoughts? - Roger Hinton 10/4/2003

The C12/4s are the right spring and I think they are the longest that Velo fitted so if you had the wrong ones you would have a lighter/slipping clutch.
The biggest difference is between the 16 and 20 spring carrier; you definitely notice that 20 springs make a heavier clutch but I guess you have 16.
The dimensions of several of the parts in the clutch and its release mechanism are critical, but the two that would make the biggest difference are the sleeve gear distance piece and the thrust pins. If you use an earlier, shorter (see CL012) distance piece then the sleeve gear nut would over-tension the springs by the differences in the length. The other determinant of the spring pre-load is the thrust pins - if you used the longer big-end/kickstart ratchet rollers instead of the shorter clutch thrust pins then the spring carrier would have to be that much further out and so pre-load the springs accordingly. However in both cases I'd have thought you would feel the springs becoming coil-bound, so it may well be that some other component out of spec. The only complete answer is to check out all the dimensions against those in the Service Manual and/or David Childs' article "Identifying the Right Clutch Parts" (in FT173, but it was one of the reprints sent out with FT a couple of years ago, or the librarian may be able to send you a copy), or with the current Tech Specialist as in the back of FT. - TW 10/4/2003

Yes, I have a sixteen spring carrier. Since the clutch was stripped and reassembled by a reputable Velo specialist shortly before I got the bike, I would be surprised if he had used the short distance piece or the wrong thrust pins, but it may be so!
On receipt of your e-mail, I quickly removed the final drive sprocket and in so doing, can see the springs sitting inside their carrier. When the clutch lever is actuated, the outer plate moves out and the springs compress slightly, but definitely don't become coil bound. As currently set up and with new plates, the spring holder has about five turns of thread visible outside of the outer clutch plate. This means that the outer face of the spring holder lies about 10 thou. 'inboard' of the sleeve gear shims when the springs are uncompressed and the front edge of the spring holder moves outward by, I estimate, 25 thou. when the lever is actuated.
Do these dimensions seem about right in your experience (if you can recall such detail!)?
If these dimensions don't seem too far out to you, and given that there is no coil binding, all this suggest to me that the resistance may, in spite of my best efforts, lie in the cable, though I can't think how. As an experiment and with the tank removed, I have tried routing it directly from the handlebar lever and above the top frame tube directly to the clutch tower. You can't get a much smoother route than that, yet I can hear the resistance in the cable when the lever is actuated.
So, I think I'll try a different cable and then decide how to proceed from there. I'm reluctant to strip the assembly yet again since in all other respects it is running sweetly, but I may be faced with it if a cable swop doesn't deliver anything. - Roger Hinton 11/4/2003

I'm not used to quite such a small 'gap' between the spring-holder and the shims, though nor am I used to one much larger. My experience has been of gaps larger than about 20 thou, but reducing it to 10 thou shouldn't make that much difference to spring pressure.
A further thought, which is that I've sometimes managed to assemble the thrust cup and its wire clip in a way that makes it noticeably stiff. This or something else binding may add to the effort required to operate the clutch. It might be worth adjusting the clutch so that it was not operated at all by the lever (ie screw the carrier out a few turns). Then the lever should require negligible effort; if it doesn't then there is something binding behind the clutch.
We'll see if anyone else can think of a reason for a heavy clutch. - TW 11/4/2003

It would appear that the heaviness was down to the clutch cable all along.
I fitted a new nylon lined cable and looped it directly from the handlebar lever to the clutch tower - light as anything, so nothing amiss in the 'works'!
Naturally, as I routed the cable along the frame top tube, more resistance crept in, but with careful routing, I've kept this to a minimum, so that everything's much lighter now. I had forgotten just how much small changes in cable routing can effect heaviness of operation. I'm not sure how much of the substantial improvement is due to the nylon lined cable and how much to being ultra careful about routing, but it's done the job.
I'll see whether the left wrist appreciates the improvement. - Roger Hinton 18/4/2003