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C: Clutch Refreshing Vincent Twin Clutch seals and pieces


craig

Well Known and Active Website User
VOC Member
In fitting an electric starter to an early Rapide, I also decided to look over the clutch and primary drive...and good thing as I found what looked to be small amount of oily items at PD20, PD22, clutch basket C1, seal C18, C20 nut, etc. Not any great amount, nothing appears on friction shoes, but damp.

I am replacing, or planning on replacing PD25 clutch sprocket seal and in the midst of this job, I am looking over all the other leakable pieces in the clutch train as well.

My questions are, as I have gone dumb on this -
Can I knock out the PD24 bush by munching up the existing PD25 seal? I am guessing the answers is yes.
Would it be best to order/replace PD24? rather than clean it up after removal? probably a good thing

Most important, once the PD25 seal is installed with PD 24 installed and the primary pieces go back into place, what tool or fixture is used to keep the PD20 sprocket centered , so as to take the deformation off the new PD25 seal?
MO14PD25Question.jpgC20C19.jpg
 
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timetraveller

Well Known and Active Website User
VOC Member
If I have understood the question correctly then the shaft of the shoe carrier keeps everything centralised in the sprocket but there is an important mod you can do while it is all apart. At the inwards end of the shaft of the shoe carrier you can machine, grind or whatever a recess about half way through the wall thickness on the inside of this. This leaves either a 'V' shape or a cylindrical recess. Make this fit an 'o' ring which will be trapped between the shaft and the PD21. The idea is to stop oil getting into, and migrating along the splines, rather than trying to stop it getting out at the outer end. That terrible idea of smothering everything in sealing compound is out of date by at least fifty years.
 

bmetcalf

Well Known and Active Website User
VOC Member
what tool or fixture is used to keep the PD20 sprocket centered , so as to take the deformation off the new PD25 seal?
I use my shoe carrier and am gentle with the seal when I have to pull the shoe carrier out. A pro would make a sleeve to suit.
 
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greg brillus

Well Known and Active Website User
VOC Member
Craig, there is a step or shoulder inside the bore of the chainwheel, this will prevent the seal coming out from the side that the thick PD 24 bushing is, you need to remove the thin walled PD 22 bush and remove/swap over the seal from this side. This usually destroys the bush, which is usually worn anyway. It is really a shorter version of the same bush in the center of the clutch plate carrier. These two bushes and the seal should ideally be changed if the chain wheel shows too much play, and even the sleeve section of the shoe carrier does wear over time and use. Use a light smear of grease on the seal and so long as there is not a sharp edge on the shoe carrier sleeve, then it should not damage the seal. Once those parts are all done, you can temporarily assemble the shoe and plate carriers on the mainshaft, do up the C20 nut with its shims up very tight, and check all your end play and shim as necessary. The outer plate carrier needs at least 10 thou end float do not be tempted to set it up with minimal play as this will cause the clutch parts to stick. It is important to check all this with the center nut C20 done up tight, if it is not, the parts that it holds will move and this will definitely cause oil leaks. Good luck with it all...........Greg.
 

vibrac

Well Known and Active Website User
VOC Member
There is a problem associated with different versions of the C20 nut I tried to search on the forum but C20 is not a long enough search term.
Hasnt one got a recess and the other not?or one is shorter than the other I seem to remember I had the wrong nut on a new bike and a deeply embeded oil seal that looked like part of the assembly it took a lot of pondering before I realised what was up .
It was a long time ago and pre forums it could be lonely in the workshop back then....
 

timetraveller

Well Known and Active Website User
VOC Member
The later nuts, I would call them 'D' nuts but someone might tell us that they came out with late 'C's, had a recess at the rear to take an 'O' ring to try to stop the oil getting out of the splines and into the clutch drum. This type of nut also required a different end to the gearbox main shaft so you cannot mix and match them. Better to stop the oil getting into the shaft in the first place.
 

bmetcalf

Well Known and Active Website User
VOC Member
a different end to the gearbox main shaft so you cannot mix and match them.
I have the counterbored nut and use an o-ring there, plus the bonded seal and hylomar on the splines. I'll have to look in 40YO, KTB, etc. to see what the different shaft detail is, so I can inspect it next time it is exposed. Touch wood, but my clutch has been dry since 1980.
 

Hugo Myatt

Well Known and Active Website User
VOC Member
Just a word of warning. About thirty years ago Tony Maughan produced a different seal in place of the C19. This comprised of a thick alloy outer ring with an O ring internally. These necessitated a much shorter C20. Whilst these Maughan seals are long unavailable there are a number of these shortened C20s still out there leading to confusion and frustration. If the clutch won't go together without locking up the shoe carrier C13 check the length of the C20.
 

vibrac

Well Known and Active Website User
VOC Member
Just a word of warning. About thirty years ago Tony Maughan produced a different seal in place of the C19. This comprised of a thick alloy outer ring with an O ring internally. These necessitated a much shorter C20. Whilst these Maughan seals are long unavailable there are a number of these shortened C20s still out there leading to confusion and frustration. If the clutch won't go together without locking up the shoe carrier C13 check the length of the C20.
That sounds like the little 'item' that foxed me all those years ago (see above)the alloy of the seal looked for all the world like part of the component it finally it revealed itself at the point of a scriber:oops:
 

peter holmes

Well Known and Active Website User
VOC Member
I am not sure that you are correct Hugo, I also had the same clutch seal mod done on one of my engines by Tony Maughan, the alloy outer ring may be a little thicker than the bonded seal C18/1 that it replaces, the internal O ring is simply compressed to the same thickness as the alloy outer ring when the C20 is tightened up, the C19 is in fact a shim washer, not a seal, the variance in between the thickness of the alloy outer ring and the C18/1 can easily be accounted for by the use of a different thickness of C19 shim, if the C20 was much shorter it would simply lock up the the C17 clutch centre bush. I think Maughan and Sons can still supply the two part clutch seal mod if asked. The real culprit can be the lip on the C17 clutch centre bush, if that lip is too thick you might have to use the very thinest C19 shim to avoid locking the clutch centre up, and that thinest shim is far to thin to be used by itself and can be a recipe for disaster if it breaks up, then the C45 spring tang has a tendency to snap off, the C20 unscrews itself and before you know it you have lost all effective use of your clutch lever, as happened to me in the middle of Dartmoor this summer, I managed to limp back to Gulworthy in 2nd gear, and then of course visited Marcus Bowden, problem solved.
 
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Hugo Myatt

Well Known and Active Website User
VOC Member
Pete,
I bow to your greater knowlege but when I reverted to the original type seal I found that in no way would the Maughan C20 fit without locking up the shoe carrier. It was definitely shorter than standard. I had to purchase a standard C20. I still have it Maughan C20 somewhere but I put it in a 'safe' place so that I would never get them confused again.
 

craig

Well Known and Active Website User
VOC Member
I am pretty sure I replaced my G3 clutch shaft assembly with a new G3/1. I would like to know the specific difference please. It appears all you need is a spacer? to convert a G3 to a G3/1?

MO16details1.jpg
 

stumpy lord

Well Known and Active Website User
VOC Member
for a picture off
I am pretty sure I replaced my G3 clutch shaft assembly with a new G3/1. I would like to know the specific difference please. It appears all you need is a spacer? to convert a G3 to a G3/1?

View attachment 25284
for a picture of G3/1 see page 136 off Into the millennium or M.P.H. 742. it also gives details. of the part C3 C3/2
For alternative methods of sealing the clutch nut see know thy beast page 118.
stumpy
 

craig

Well Known and Active Website User
VOC Member
Thanks stumpy, I went and found my 742 and was amazed to find pictures of the shaft end. I had never seen a G3/1 and it's clutch end modification. Now I see how a G3 coiuld be made into a G3/1 with a spacer.
I hope it is okay to share the page 11 & 12 of MPH.
Craig

I am disappointed that C20 and C20/1 are not shown and discussed, and that a photo or better yet cross sectional drawing of the assembled G3/1 and C3/1 are not shown.


MPH742Pg11&12.jpg
 

craig

Well Known and Active Website User
VOC Member
My KTB, forth edition VOC 2003, has the C18/1 and C18/2 combination seal discussed on page 129.
Thank you.
A seal combo for me to consider.
 
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vibrac

Well Known and Active Website User
VOC Member
There is a problem associated with different versions of the C20 nut I tried to search on the forum but C20 is not a long enough search term.
Hasnt one got a recess and the other not?or one is shorter than the other I seem to remember I had the wrong nut on a new bike and a deeply embeded oil seal that looked like part of the assembly it took a lot of pondering before I realised what was up .
It was a long time ago and pre forums it could be lonely in the workshop back then....
Thank you all for helping me remember
 

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