C: Clutch Multi-Plate Clutches

[eharris]

Evening all,

Having got the bike on the road (see the “It works!” post), I have taken it out for a bit more of a run and discovered the clutch both drags at low speed and slips at higher speed (55 in top), so I am now faced with the question of how to approach this.

It has a standard clutch and I fitted a new friction plate and springs when I had the primary drive off to fit a D ESA. Whilst I am confident that I put it all back together in the right order, there is a significant chance I didn’t set it up as accurately as it could have been.

Where I am going with this is that I would like to get some use of it this summer, so I would like to be able to get to the point of having a reliably working clutch as quickly and simply as possible, which could be that I fit one of the Spares Co multiplate clutches.

I do realise that the standard clutch can work very well, but my fear is that mine will take a lot of tinkering to get there.

What are your thoughts?

 

[eharris]

I fitted a one piece lightning style clutch plate in place of the cork inserts and at the same time replaced the inner and outer driving plates. It took quite a while to bed-in and stop dragging, but is now beautiful.

Thanks. My new friction plate is the bonded type.

I am confident I could sort the dragging out, but it is the slip at higher power that concerns me as that implies the servo part isn’t working correctly.

 

[chankly bore]

To get the C29 springs even, use ET98 thrust washers as needed. They are, or should be, .025" thick.

 

[BigEd]

Evening all,

Having got the bike on the road (see the “It works!” post), I have taken it out for a bit more of a run and discovered the clutch both drags at low speed and slips at higher speed (55 in top), so I am now faced with the question of how to approach this.

It has a standard clutch and I fitted a new friction plate and springs when I had the primary drive off to fit a D ESA. Whilst I am confident that I put it all back together in the right order, there is a significant chance I didn’t set it up as accurately as it could have been.

Where I am going with this is that I would like to get some use of it this summer, so I would like to be able to get to the point of having a reliably working clutch as quickly and simply as possible, which could be that I fit one of the Spares Co multiplate clutches.

I do realise that the standard clutch can work very well, but my fear is that mine will take a lot of tinkering to get there.

What are you thoughts?

Small steps, minimum dismantling:-
The primary clutch will transmit enough power to get you up into the fifties just as you have found. It will get you home if you have a problem with the main clutch. (When an oil seal failed I rode from Wales to my home in the Midlands on the primary clutch.) If you can get into the fifties then your primary is driving as it should. If it is dragging check the adjustment:

1. Adjust the clutch cable. You will find some help at this link: Clutch cable adjustment See post #3.
2. Remove the clutch cover. You have some pushrod clearance adjustment at this end should you need it. If your primary is driving OK your clearance is probably OK. Pull in the clutch lever and see how much lift you have. You don't need much but the plate should lift square to the friction plate. If it lifts OK then it may not be lifting evenly. Engage a gear and rotate the rear wheel. (This is easier if you have the spark plugs removed or the valve lifter lever engaged. I pull the handlebar lever back and hold it back with a re-usable tie-wrap.) Check to see if the plate wobbles as it turns. If it does then the spring spacers may not be all the same lengths or the springs may be of different lengths. Remove the springs and check spring and spacer lengths. There are ways to help the plate lift square. Timetraveller produced a needle roller bearing that helps. I shortened the clutch pushrod and used an old valve (from an Austin mini?) to help keep things square.

At this stage you are looking at more dismantling:-

1. Have look and see if there is oil in the clutch drum or on the clutch shoes. If you have oil here then it may be that oil is finding its way along the mainshaft. There should be a seal C18 fitted to the C3 shoe carrier. Some sealant applied to the splines when assembling can sometimes help here.

If you have already fitted a 'D' shock absorber you know that to check the next two seals requires the removal of the clutch drum:-

1. There is also a seal PD25 between the two bushes in the chain wheel.
2. There is a large diameter seal PD26/1 fitted in the outer case.

On the brighter side, If there is no oil contamination you can remove the clutch shoes without much dismantling. If the linings look oil-free and in good condition then adjustment of the clutch plungers may be needed.

Maybe that is enough to be thinking about for now. There are lots of posts on clutch problems. Sorting the 'wheat from the chaff' is tedious.
Maybe a good starting point is here:- https://www.vincentownersclub.co.uk/threads/jig-to-hold-head-in-lathe.16283/page-4#post-148672

 

[Bill Thomas]

There is so much lift on the single primary plate,
I don't think the trouble is there,

T.T. on THIS Forum, !!, Does a thrust mod' that is well worth fitting , For lifting the outer plate Square.

I think we all, ?, At some time blamed the outer plate,
But later found it is the shoes that are the problem,
Worth spending some time on the standard clutch, I think,
Lots of Information on here.
Good Luck, Bill.

 

[bmetcalf]

Lots of info here: https://www.vincentownersclub.co.uk/resources/categories/3-4b-twin-clutch.59/

 

[eharris]

Thank you all (esp. BigEd for his comprehensive reply). I'll have a bit of a tinker this evening and try bringing it in to work on Tuesday (I have been talking about this bike for so long that some of my colleagues are starting to wonder if it really exists, a variation on the geek's imaginary girlfriend!).

Anyone want to comment on the difficulty to install and setup the VOCSC multiplate clutch?

 

[highbury731]

When I started looking at my clutch, I found that the inner and outer plates for the primary clutch (these may be C21 and C23 - I am not near my parts book to check) were conical and far from flat. I set to with coarse wet'n'dry and a sheet of glass. After lots of rubbing they are nice and flat

 

[stu spalding]

When I started looking at my clutch, I found that the inner and outer plates for the primary clutch (these may be C21 and C23 - I am not near my parts book to check) were conical and far from flat. I set to with coarse wet'n'dry and a sheet of glass. After lots of rubbing they are nice and flat

I was told that the plates C21 & C23 are meant to be slightly dished as they flatten under spring pressure when the clutch is fully engaged. Cheers, Stu.

 

[BigEd]

As I suggested earlier, if you can get up to around the 50 mph mark your primary clutch is driving adequately. The problem almost certainly lies with the main clutch. If you don't find the cause of the slipping main clutch to be oil contamination you might remove the clutch shoes and see if the lining in the C7 shoe has been drilled to give access to the plunger adjustment screw. It is easy to drill the lining in line with the plunger if it hasn't been done. Slacken it off a turn, test and see if it grips any better. If it slips the plunger has too much pressure. if there is not enough spring pressure the clutch will tend to bite abruptly.
It is a bit suck it and see to get a feel for it but you do get good at taking off and refitting the primary clutch, etc.
P.S. In the 60-70 years that these bikes have been around there is no telling what a previous owner may have done so check all the parts carefully.