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C: Clutch Refreshing Vincent Twin Clutch seals and pieces


peter holmes

Well Known and Active Website User
VOC Member
Notice how I said, unless it has one of the dowty type spacers, I will refit what came out to retain the correct distance for the nut verses C 17 bush clearance plus a shim as necessary. The point was to prevent an oil leak from this area, and that is generally how I do it, nothing special but it seems to work.
Understood now, so when a Dowty seal fails you retain the metal ring and replace the damaged or missing rubber seal with Threebond, sounds perfect to me, what threw me a little was when you referred to the flat surface of the C3 carrier.
 

craig

Well Known and Active Website User
VOC Member
so to modify the inboard end of the C3 clutch shoe carrier, you can simply use a valve grinding stone to angle cut a bevel to allow a simple 022 oring to fit up against the spacer ?
C3 up against PD21.
Is 30 degrees the best angle?

where do you find a valve stone with shaft for home use?
i can supply a drill press with holding vise,



30DegreeStonePic2.jpg
 
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BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
so to modify the inboard end of the C3 clutch shoe carrier, you can simply use a valve grinding stone to angle cut a bevel to allow a simple 022 oring to fit up against the spacer ?
Is 30 degrees the best angle?

where do you find a valve stone with shaft for home use?
i can supply a drill press with holding vise,



View attachment 25387
I don't think the angle is important as long as the "O" ring protrudes a little from the end of the "C3" so that it is compressed when everything is tightened up.
 

timetraveller

Well Known and Active Website User
VOC Member
Big Ed is right but I used the back side of the grind stone which was at 45 deg, not 30 deg. I bought these stones decades ago and they came as standard with 30 deg on one side and 45 on the other. If you have access to someone who is a good machinist then I would get them to machine a proper recess inside the end of the tube part of the C3. I used the grind stone dodge because my lathe's four jaw chuck would not take the diameter of the large side of the C3. I do not want to 'go on' about this mod as everyone has their own way of doing things but it really is easy, totally effective and stops oil getting into the splines rather than trying to stop it getting out at the other end.
 

highbury731

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VOC Member

craig

Well Known and Active Website User
VOC Member
I have now in hand what appears to be the correct parts to convert my C20, C3, G3 early configuration to C20/1, C3/2, G3/1 allowing the use of a simple o-ring to provide the seal at the clutch nut.
I made up a simple drawing to illustrate this change..............and now I have some questions about this "late model" up grade. The dark green G3mod threads on to a G3 to convert to G3/1.

ClutchNutC20_1LargeTV.jpg

1) This new configuration calls for a shortened C20/1 nut that gives up the indexing feature of the old style C20 and simply tightens up against a new C3/2 that provides just a flat surface.
C3/2 does not fit tight on the shaft, neither did the C3.....isn't this indexing early feature a better mechanical design?

2) Physically, upon assembling the pieces, there appears to be enough room at the C18/2 o-ring slot to allow 2 o-rings stacked in the slot . Is this the case with other installations?

3) Is this drawing accurately depicting the configuration? I know the drawing is not to scale.

Thanks for any help on this.
Cheers
Craig
 
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craig

Well Known and Active Website User
VOC Member
Here is my drawing on the early parts , and showing a new style C18/3 seal.
This shows the indexing of C20 and C3.

ClutchNutC20LargeTV.jpg
 

timetraveller

Well Known and Active Website User
VOC Member
As an astronomer and not an engineer I might be missing some important point here but why would you choose to do all this when a simple modification to the rear of the shoe carrier tube can completely cure any oil ingress. It works with either the early or later type of gearbox main shaft etc. If there is a good reason then let us know as I do not want to be advising people to do something which is prejudicial to the longevity of their bikes.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
As an astronomer and not an engineer I might be missing some important point here but why would you choose to do all this when a simple modification to the rear of the shoe carrier tube can completely cure any oil ingress. It works with either the early or later type of gearbox main shaft etc. If there is a good reason then let us know as I do not want to be advising people to do something which is prejudicial to the longevity of their bikes.
I was thinking the same thing.:confused:
 

craig

Well Known and Active Website User
VOC Member
As an astronomer and not an engineer I might be missing some important point here but why would you choose to do all this when a simple modification to the rear of the shoe carrier tube can completely cure any oil ingress. It works with either the early or later type of gearbox main shaft etc. If there is a good reason then let us know as I do not want to be advising people to do something which is prejudicial to the longevity of their bikes.
Great C3/PD21 o-ring seal solution, thank you, but I want to know the details of the old/new C20, C3, G3 pieces.

I am looking at the "new" pieces and wondering why? no indexing? loose o-ring?
As an engineer I need to know all the details where possible, then make a decision.
In this clutch shaft case I can see multiple seals applied.

I don't understand why the C20/C3 indexing is lost and C3/2 allowed to wobble on the G3/1.
This is not a issue?, never been an issue? 2 million miles on a D with no clutch leaks?

I understand that C20 nut comes loose as standard fare?
Have I seen instructions to leave C20 nut loose to allow no binding in the clutch action?
Why is the groove to take the new C18/2 o-ring seal deep enough to take two o-rings?
Does the alloy spacer in use with a C18/3 crush down allowing loose C20/C3 interface?
Do you over torque a C20 nut to allow the spring lock, or do you back off the C20 torque?
Is there a torque spec for C20 nut beyond KTB?

Cheers
Craig
 
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timetraveller

Well Known and Active Website User
VOC Member
Craig, the C20 nut does not come loose as standard. It is locked into place by the tang on the C45 spring. Originally, and possibly even now on new ones, this tang was bent through 90 degrees with rather a sharp bend. This would fatigue and break. Whenever this happened I would bend a new tang with a generously radiused corner and I have never had one break after that.

There are not multiple seals applied.. The early ones had a bonded item under the C20 and sealing compound on the gearbox mainshaft where it passes through the C3 shoe carrier tube. Later this was replaced by the C20 being modified with a recess to take the now cylindrical end of the gear box main shaft. Both ideas were intended to stop oil getting out of the splines inside the C3 and on the outside of the gearbox main shaft. My idea stops it getting in there.

Your paragraph concerning indexing of C20/C3 etc is not correct and you need to go back and either read the books/ instruction sheets or look at the parts and understand how they are intended to work.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I always thought what made the nut loose was wear on the shim in the gearbox, Which I have seen almost worn to nothing, And the tang of the spring still in place. Cheers Bill.
 

stu spalding

Well Known and Active Website User
VOC Member
Neville Higgins recommended that nut C20 be fully tightened, then tightened further to line the locking slots up, never loosened. Cheers, Stu.
 

timetraveller

Well Known and Active Website User
VOC Member
Bill, I've never seen the nut loose other than when the tang on the spring failed. I am not sure how it can come loose when the nut is prevented from rotating on the main shaft by the spring tang. Confusedly yours
 

Bill Thomas

Well Known and Active Website User
VOC Member
The Shim E76 wears, We did one a few years ago, It had worn down to a thin ring, And somebody could not see it and put a new shim in there, Which took all the end float out of the input shaft.
Lucky I always give the gear box shaft a push pull, When the Clutch is off, I like to feel a bit of endfloat.
Cheers Bill.
 

greg brillus

Well Known and Active Website User
VOC Member
The shim wears because the C20 nut is not tight and the whole lot starts to move. This is also what causes most leaks, I feel it is because owners, or previous owners did not do the nut up tight enough, perhaps because they did not have the correct tools to do so. An equal amount of harm can be done by things being left loose as it can by over-tightening.............
 

stumpy lord

Well Known and Active Website User
VOC Member
The shim wears because the C20 nut is not tight and the whole lot starts to move. This is also what causes most leaks, I feel it is because owners, or previous owners did not do the nut up tight enough, perhaps because they did not have the correct tools to do so. An equal amount of harm can be done by things being left loose as it can by over-tightening.............
In forty years on , one will find a simple tool that every twin owner should have in his tool kit. It is simple to make , and will fit in the tool tray. I t enables the clutch to be held so that the C20 nut can be fully tightened up without having to jam any thing, and risk causing any damage.
details can be found on page220 of forty years on article 58 or M.P.H. number 470
stumpy lord
 

craig

Well Known and Active Website User
VOC Member
I am not sure how much torque could be applied to the C14 clutch plate pins while tightening the C20 clutch nut using this tool.
Welding or bolting a handle to an old C21 clutch plate might be easier method of fabbing this tool.

ClutchHoldingTool.jpg
 
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