Clutch springs

Paul Marx

Paul Marx

Hero member
Location
France
The clutch pull on my wife's 500 seems heavy. All the usual causes have been ruled out. I had the clutch out this Autumn but cannot remember if I measured the springs.
Would worn, shorter springs give a heavier pull?

Paul
 
No. They would only have less pre-tensioning, therefore actually offering lighter action.

Check and lube the actuating lever pivot and pushrod, adjust the screw to optimise lever geometry, eliminate excessive slop. Check and lube handlebar lever pivot and cable, or better still, fit a new cable.

I can supply NOS cables and new repro springs if needed.

piet
 
sfcpiet said:
No. They would only have less pre-tensioning, therefore actually offering lighter action.

Check and lube the actuating lever pivot and pushrod, adjust the screw to optimise lever geometry, eliminate excessive slop. Check and lube handlebar lever pivot and cable, or better still, fit a new cable.

I can supply NOS cables and new repro springs if needed.

piet
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Thanks Piet. Thought so.
Cable is a new Venhill. Lever is a new Magura style dog leg. Changed all that this afternoon.
Clutch is still heavy.

I'll go and have a look at the lower end.

Paul
 
Compare the lever ratio of the new with the old. All dog leg levers do is place the lever closer to the bars, means less cable travel, slop and other deficiancies need to be reduced to an absolute minimum to retain maximum disengagement.

piet
 
If it were me I think I would stick new springs in whilst I was in there anyway.
Just a thought , and I may be wrong , but if the springs are worn , ie shorter than their minimum length limit , then cable free play would need to be adjusted to compensate , meaning that the cable is trying to operate an increasingly (in effect) coil-bound spring , leading to a heavier action , maybe...
Or , to take it to the extreme , imagine how impossible it would be for a (properly adjusted) cable to operate a completely compressed (shorter) spring.
 
Last edited:
rocketonarail said:
If it were me I think I would stick new springs in whilst I was in there anyway.
Just a thought , and I may be wrong , but if the springs are worn , ie shorter than their minimum length limit , then cable free play would need to be adjusted to compensate , meaning that the cable is trying to operate an increasingly (in effect) coil-bound spring , leading to a heavier action , maybe...
Or , to take it to the extreme , imagine how impossible it would be for a (properly adjusted) cable to operate a completely compressed (shorter) spring.
Click to expand...
I should have put in new springs but I'm careful with my wife's budget even though I put € 1000 of my own hard earned pension money into that bike.
Now she wants to ride it and I want to tinker with mine.

Paul
 
Paul, when I rebuilt my 3c, Redaxed engine, the clutch pull was massive, did all the usual things to fix it but the thing that made the most difference was the length of the pushrod.
As Piet has mentioned before, the pushrod is in my experience quite significant.
Think from memory we lengthened it by 1.5 mm, massive difference.
3c clutch is now lighter that Jota's hydraulic clutch.
 
In stock form, the springs cannot be adjusted in any way and cannot bind. Preload also decreases with friction plate wear. Only option is adding washers/spacers to increase pre-load. If too much is added, the springs MAY become coil-bound when the clutch is disengaged.

The adjuster screw at the pushrod allows for attaining proper geometry at the actuating lever, much like slightly lengthening the pushrods in the triples. This alone can account for about a 30% lighter clutch action.

Clutch plate wear actually pushes the actuating lever into a more advantageous postion, cable play would need to be increased, ie, cable adjuster screwed back in, to compensate.

piet
 
The cable clutch on my Pantah was almost as heavy as my 3c, while at the local vintage Ducati shop I tried the clutch on their race Pantah and it was much lighter than mine, I asked and their fix was an Aprilia lever and perch. Better Geometry, but just like the extended lower Laverda trick it needs minimal play to get neutral. It was a nice cheap fix for $60 oz. I would have made my own lower extended lever but there is no room on a Pantah to do that.
 
My poor Corinne had cramps in her left hand last time out aven though I'd mounted a new cable and a dog leg lever.
So, time to take all the clutch paraphernalia off the right hand side of the bike which will also allow me to change the clutch rod oil seal. Well, I may well have found the problem. It would appear that the ball between the two rods is missing. I can't be sure because I cannot get the clutch side rod out of the mainshaft but peering down the shaft with a torch doesn't reveal a ball.

Paul
 
Stick one of those telescopic magnet things down the hole if you can find or make one of small enough diameter. If it doesn't come out with a ball on it, then I reckon you need to take the other side off so you can push the rod right through. Then you can make a decision about whether you need to do anything about the pushrod setup.
 
Loose 2mm of length with these combinations and that has a massive effect, years ago I made a replacement rod out of silver steel after a set of new plates caused an issue and the soft new rod wear away a bit less than 2mm in an hour of use losing the clutch totally, the ends need to be case hardened as they take huge point loads. There is a dimension that the 2 rods and ball-bearing absolutely need to be, from memory it's 112mm but check to be sure.
 
Stuck a length of coat hanger down the shafts, with magnets. Nothing.
Turned the bike over on the starter whilst leant over to the right. Nothing.
Poked a screwdriver blade down there, a ball would feel different from the end of a rod, no ball contact.
Seems to confirm what I could see on all fours, peering down the shaft with a torch.

Paul
 
no ball = no good of course, but from experience a Venhill clutch cable can seize solid, it may be on the way out, when I recovered longshanks from some point in Europe and took his bike (GTL) to Wagners, we all thought a mechanical problem had occured on this newly renovated bike, no-one dreamt it was the bleeding Venhill cable, not even King Kong could have moved the clutch lever, not even a hydraulic clamp would have squeezed it, it was as though there was an invisible block of wood between the lever and handlebar (I think you get the picture), a week later it was fitted with a German totally conventional made cable and was fine, (and still is five years later) the old cable (off the bike of course) was then clearly seized and could not be slid in or out at all.
this happenned in about 700 miles from James house, and started fairly early, got worse, then was 100% duff, he didnt even bother going back to Venhill after my experiences a few weeks early, life is too short.
try to actuate the clutch with the cable off Paul.
CLEM
 
CLEMTOG said:
no ball = no good of course, but from experience a Venhill clutch cable can seize solid, it may be on the way out, when I recovered longshanks from some point in Europe and took his bike (GTL) to Wagners, we all thought a mechanical problem had occured on this newly renovated bike, no-one dreamt it was the bleeding Venhill cable, not even King Kong could have moved the clutch lever, not even a hydraulic clamp would have squeezed it, it was as though there was an invisible block of wood between the lever and handlebar (I think you get the picture), a week later it was fitted with a German totally conventional made cable and was fine, (and still is five years later) the old cable (off the bike of course) was then clearly seized and could not be slid in or out at all.
this happenned in about 700 miles from James house, and started fairly early, got worse, then was 100% duff, he didnt even bother going back to Venhill after my experiences a few weeks early, life is too short.
try to actuate the clutch with the cable off Paul.
CLEM
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The cable is new Clem. And yes, Venhill cables have a short life expectancy.

Paul
 
did you not say it was a Venhill Paul?
if so, bin it, and get a totally conventional one made up. Just like the things that were made for about 90 years and then came along "easy slidres or super slickers, nylon lined" etc etc,

the cable on my 1935 Sunbeam are original and work great, but then they should it has only a few years ago passed 20,000 miles from when my uncle bought it new and is now only 100 or so past that.
CLEM
 
CLEMTOG said:
did you not say it was a Venhill Paul?
if so, bin it, and get a totally conventional one made up. Just like the things that were made for about 90 years and then came along "easy slidres or super slickers, nylon lined" etc etc,

the cable on my 1935 Sunbeam are original and work great, but then they should it has only a few years ago passed 20,000 miles from when my uncle bought it new and is now only 100 or so past that.
CLEM
Click to expand...
It is a Venhill Clem, but new. I have a few standard cables as well including the well lubed one that was on the bike before. If the ball between the rods is missing, the cable becomes a secondary issue.
Paul
 
Both my bikes have Venhill clutch cables and they are fine, have been on for bloody years. I also have made all my throttle and choke cables with their nylon liner kit and they also are great. We know that you have issues with them responding to complaints.
 
Well, that's a lot better.
Put the proverbial 1/4 inch ball, aka 6.35mm in between the two push rods after having checked the right hand rod for straightness. There was therefore no ball in there. Greased the mechanism, used a NOS cable I had and clutch is a lot lighter. Far from a one finger job however. I hope the Mrs will cope. The setup as it was before meant that either neutral was impossible to find, so agony for the left hand in town, or neutral could be found, but a very heavy clutch action.
We have a rally planned Saturday. I'll test it tomorrow before she gets back from Italy Thursday pm.

The only bodger I trust is myself, I hate all the others.

Paul
 
Paul Marx said:
Well, that's a lot better.
Put the proverbial 1/4 inch ball, aka 6.35mm in between the two push rods after having checked the right hand rod for straightness. There was therefore no ball in there. Greased the mechanism, used a NOS cable I had and clutch is a lot lighter. Far from a one finger job however. I hope the Mrs will cope. The setup as it was before meant that either neutral was impossible to find, so agony for the left hand in town, or neutral could be found, but a very heavy clutch action.
We have a rally planned Saturday. I'll test it tomorrow before she gets back from Italy Thursday pm.

The only bodger I trust is myself, I hate all the others.

Paul
Click to expand...
Hi Paul It can take a bit of mucking around to get that neutral position set up on a 500 (well I found that on my bike).
You have to remove the clutch and very fine tune the centering of the push pull forks on the selector drum.
I got mine a lot better but its still not perfect.
 
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