Clutch problem.

TommoT · Post by **TommoT** » Mon May 08, 2006 12:07 am

quote:
I totally sympathise with you Andy, I have exactly the same problem with a '65 heavyweight 500 single, and have been unable to resolve it. Does anyone Know if we should be using handlebar levers with 7/8" or 1 1/8" pivot to cable nipple centres? This may be the next thing we should try.
Derek Cooper

7/8th should be correct. But I am not convinced it'll solve your problem

cleancut · Post by **cleancut** » Mon May 08, 2006 12:25 am

quote:
quote:
I totally sympathise with you Andy, I have exactly the same problem with a '65 heavyweight 500 single, and have been unable to resolve it. Does anyone Know if we should be using handlebar levers with 7/8" or 1 1/8" pivot to cable nipple centres? This may be the next thing we should try.
Derek Cooper
Derek, The lever on my bike measures 1.1/8" between centres.
I've already been advised to increase this somehow but I'm not sure how or whether I can purshase one.
My next move is to experiment with the lever profile. If I get a result I'll let you know.Thanks, Andy.

7/8th should be correct. But I am not convinced it'll solve your problem

Biscuit · Post by **Biscuit** » Mon May 08, 2006 12:32 am

I repeat - increasing the pivot radii on the handlebar lever will not solve your problem. Experimenting with the cam contour will - but why should it be necessary?

cleancut · Post by **cleancut** » Mon May 08, 2006 12:44 am

quote:
Surely different pivot radii would just increase the clutch disengagement, the problem of engagement at the last moment would still remain.
Allan, I dont intend altering the pivot radii. What I wish to achieve is a more gradual feed by flattening out the curve that plays on the push rod. It's just an exersise with no guarantees.
Nothing ventured, etc.
Thanks again, Andy.

Steve Martin · Post by **Steve Martin** » Mon May 08, 2006 2:00 am

Hello, I've been trying to take this issue right back to the basic push rod factors to understand what might be done.
I've yet to actually measure the various movements involved; but is it not fair to say that on these boxes the total push-rod movement is quite small, say 3/16"?, and the movement from 'bite' to 'fully in' is thus even smaller? With the small amount of push-rod clearance, and cable free-play, the 'take-up' movement is inevitably going to be at the end of the H'bar lever travel. Moving that take-up range to the middle of the lever throw would not, of itself, increase the rate of feed; though it might make for an easier hand action. It would need some form of modified linkage to significantly increase the ratio of lever to cam travel to produce the slower feed being sought. I'm not sure that the longer 'pivot to cable' levers would have enough effect.
Most of my riding has been on machines with this clutch; and yes, it does take up with the lever nearly out, and yes, it can be hard work! Attention to all the relevant factors will improve it, but the fact remains it requires a certain strength and stamina, and a 'feel' for the fine control needed in heavy traffic.
Depending on the rider, there are a couple of other factors worth considering. A 'modern' bike riding friend of mine is frequently amused/amazed at many of the features common on '50s machines; [ 'bicycle tyres', fixed footrests, 'where's the starter button?']; but most of all, the clutch action, requiring the whole hand rather than one finger! I think a young rider,on turning to a classic machine, might well believe that there was something wrong with a 'normal' clutch set-up. At the other end of the scale, none of us are getting any younger, and some bits don't work as well as they used to, and some things are getting harder; perhaps clutch operation is one of them?
I'm not dismissing the idea of research and experiments to improve matters, but the real root of the problem, as perceived by each rider, needs to be made clear first. I have, in my Sunbeam S8 'goody box' a clutch linkage modification, which on a good day I think I understand, and the AMC Archive technical site contains a diagram and instructions for a similar device for a G12. Both are claimed to significantly reduce the effort required, by increasing the lever ratio. I think these are more likely to achieve the desired results than the minor changes possible in the box itself; the down-side is that you have to make it yourself!
Cheers, Steve.

itma · Post by **itma** » Mon May 08, 2006 10:31 am

At the risk of getting myself tied up again, all the the AMC clutches I had were sweet and light.
But then they were all AMC bits.
I don`t know what the friction plates are made of these days, but to me the answer lies in the plate material rather than the mechanics. The pattern stuff seemed very "spongy " to me , far too thick, which is why I used to skim them, the bonded on sorts anyway

The second biggest source of clutch heavyness is this passion for clipping the cables tightly to the frame, looks over function; never done new,mucks things up a treat, tho` not the cause of this problem .
nice easy sweep and lots of oil needed.Edited by - itma on 08 May 2006 09:36:20 AM

lawrence · Post by **lawrence** » Mon May 08, 2006 8:37 pm

At the risk of over simplification could this not simply be that the clutch springs are overtightened? they should be screwed in until the tops of the nuts are just flush with the cover and then be slightly adjusted to get even rotation. it wants to be only tight enough to avoid slip. A lot of people screw them in way too tight giving a heavy clutch and lack of feel.

All my classic clutches are , like Ken's, sweet and light and easy to operate.(except Veronica who is definitely not trying to give me a light clutch)

Dave Walker · Post by **Dave Walker** » Tue May 09, 2006 1:00 am

I've got my clutch better than I've ever had it (57 twin amc box, 56 clutch) but it is pretty much as you describe it with the take up right at the end of the lever travel. It takes me by surprise every time I get on it after the modern Bee Em.

Call me a defeatist but I'd say if you can get neutral at rest & it doesn't slip you're not doing too badly.

The first time I rode it after many a long year my left hand was aching after 35 miles along country lanes.

The improvement I achieved was a result of not tightening the spring nuts so far & I'm inclined to think I could go further still with slackening them. Next time I have the chaincase open I fancy to keep slackening them until it starts to slip & then tighten them up a bit & leave it.

cleancut · Post by **cleancut** » Tue May 09, 2006 9:29 pm

quote: Dave, Thanks for your view on the problem. I'm comeing round to thinking along the same lines. The clutch itself is no problem with neutral easily found at rest and no slip even powering up the steepest hill. It's also light at the lever so I think I'll through the towel in until next time I have the gearbox cover off. Then I'll try my idea with the re-profile. I'll accept it as being part off the character of the bike.
Thanks again,Andy.
I've got my clutch better than I've ever had it (57 twin amc box, 56 clutch) but it is pretty much as you describe it with the take up right at the end of the lever travel. It takes me by surprise every time I get on it after the modern Bee Em.

Call me a defeatist but I'd say if you can get neutral at rest & it doesn't slip you're not doing too badly.

The first time I rode it after many a long year my left hand was aching after 35 miles along country lanes.

The improvement I achieved was a result of not tightening the spring nuts so far & I'm inclined to think I could go further still with slackening them. Next time I have the chaincase open I fancy to keep slackening them until it starts to slip & then tighten them up a bit & leave it.