C: Clutch Clutch plunger spring adjustment

Bobv07662

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The clutch on my 50 Rapide is a bit grabby. I've had a quick look behind the cover and the good news is that it's dry inside. The bad news is the C11 plungers are not touching the pins. They are about 1/16 from contact. I've read where the adjusting screw C12 can be accessed by drilling a hole in the linings. My question is can I drill that hole large enough to remove C12 in order to check or replace the plunger springs without affecting the service life of the linings?
 

Bill Thomas

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Bob, As long as the springs are still springy, I fitted a pair of cut down C15 tubes,
And slipped them over C14 pins, Where C11/1 touch, Tricky job I think .
 

stu spalding

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Hi Bob, as long as the plungers aren't hardened (some are), and the gap between plunger and pin is only small it is possible to undercut the collar on the end of the plunger thus dropping the plunger in to take up the slack. I recently did a clutch where the pivot bores had been "reclaimed" by stuffing a 5/8" drill through the hole where it stood and bushing. This is all wrong as it locates the plungers away from where they should be, the only way to reclaim pivot bores is by jig drilling. There are a couple of articles in MPH 820 & 821 which may be of help. Cheers, Stu.
 

BigEd

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I don't think that a bit of clearance at the end of the plungers is a problem. There is a counterbore in the hole for the plunger that limits how far it sticks out.
If your clutch is grabby the first thing I would do is to make a hole to get access to the adjusting screw for the plunger and increase the tension on just the C7 shoe. Too much pressure and the clutch will slip, to little and it will grab. Use small increments maybe 1/4 - 1/2 a turn at a time. In your case try taking a little off. You will soon see if that is an improvement. It is a bit of a pain removing and refitting the shoes after adjustment. Leave the clutch cover off for a quick test ride, keep your trousers away from the clutch.
It is quite complicated compared to a multi-plate clutch and difficult to understand how it works when you first look at it. (Or even the 2nd, 3rd, 4th ... time. ;)) Mine has quite a lot of "slop" in it, I really should replace some of the worn bits. It does, however, work well and has a very light action at the clutch lever. I removed a multi-plate clutch to fit the original once I'd got a bit of an idea about the adjustments.
Clutch shoe assembly2_cropped.jpg
 

stu spalding

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In order for accurate adjustment of the clutch to be obtained, what is required is a dummy centre (pictured). It's a simple turning job in hard plastic. This removes all guesswork from setting the thimble C12 to the right depth. Simply assemble the clutch on the centre and adjust C12 until the shoes expand to six inches when actuated. It is essential that the travel of the plunger in C7 is absolutely smooth as the slightest resistance will result in a grabby clutch. People have been saying for 70 years "Oh, it wouldn't be a little thing like that" but it is. I spent a great deal of time and effort in 2014 sorting out exactly what makes the twin clutch tick and when it's right it is light, progressive and smooth in operation, when it's nearly right it's a piece of junk. Cheers, Stu.
P1050864.JPG
 

vibrac

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I think Stu has got that absolutely right. I have finally decided that the original clutch is the thing for the road (And bear in mind my first major job on a Vincent was to fit a Norton clutch to my first twin from a article in a mag when I was still at my first job 196*) - not that I have an original clutch fitted on my twin because I dont have a road one anymore its a racer and a belt drive with a newby clutch that is either in or out is just the job on the track.
 

greg brillus

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Imagine all those years ago when folk gave up on clutch and gearbox issues............Out with a bloody big hack saw........... The horror of watching someone do it ..........The shame, the shame......... o_O
 

Bobv07662

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In order for accurate adjustment of the clutch to be obtained, what is required is a dummy centre (pictured). It's a simple turning job in hard plastic. This removes all guesswork from setting the thimble C12 to the right depth. Simply assemble the clutch on the centre and adjust C12 until the shoes expand to six inches when actuated. It is essential that the travel of the plunger in C7 is absolutely smooth as the slightest resistance will result in a grabby clutch. People have been saying for 70 years "Oh, it wouldn't be a little thing like that" but it is. I spent a great deal of time and effort in 2014 sorting out exactly what makes the twin clutch tick and when it's right it is light, progressive and smooth in operation, when it's nearly right it's a piece of junk. Cheers, Stu.View attachment 36917
Stu, Turning that dummy center is something easy for me. What I'm missing is the "assemble the clutch on the center"...Do I remove the shoe/carrier assembly and then place the dummy center inside that shoe/carrier, then adjust the C12s to get the expanded shoes to measure 6"?
Also, how do I make sure both shoes are expanding equally? Just measure to the center of the dummy center tool?
Thank you for your insight into these clutches. I do see how the clutch operates, it is the seeing how to make it operate properly that I now find myself tackling! I have quite a bit of experience on automotive single and multiplate clutches and have never seen a clutch as elegant as these in a Vincent. It is what makes these bikes unique.
 
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