Clutch not fully disengaging when hot

[Yves.Astein]

Hi all,

Quick question. I have replaced the clutch plates with new ones in my 51 G3. Everything works smoothly, until the clutch starts getting warm after a couple of miles. Then, when I come to a stop. The clutch will not disengage completly and feels sluggish using the clutch handle. As I said all clutch plates are brand new. I suspect, that the plates are warping when getting warm. Is there a remedy for that ? Should I try to heat up the friction plates evenly to remove tensions ?
Or could there be a nother reason. While riding, i am not experiencing any drag.

Thanks

[SPRIDDLER]

O.K. I'll stick my neck out and let you have some thoughts to start the ball rolling.......

I have replaced the clutch plates with new ones in my 51 G3.

I'm assuming the clutch didn't show the particular problem before you changed the plates and that the new plates have bonded friction material, not cork.
I'm also assuming that you have tried re-adjusting the clutch to try to cure the problem.
The 1951 Owners Manual and Spares List in the Archives shows a CP gearbox whereas the 1951 Workshop Manual shows a B52 gearbox. I don't think it has any relevance to the problem but it may help to know which one you have - the B52 or the CP gearbox.

Everything works smoothly, until the clutch starts getting warm after a couple of miles.

The clutch plates will only become noticeably hot when they are slipping and not at all when fully engaged whilst riding along.
In any case, unless you are doing a series of Boy Racer starts, or pulling away uphill vigorously from rest or with a sidecar attached and slipping the clutch for longer than a couple of seconds I doubt very much that they would get hot enough to warp.

Then, when I come to a stop. The clutch will not disengage completely and feels sluggish using the clutch handle. As I said all clutch plates are brand new.

The new plates will have 'sharper' edged tangs/ears than your old (worn) plates. If their locating points in the clutch hub or basket have become worn (ridged/scalloped) over time (and that does happen) the new plates may not be moving outwards freely when you operate the h/bar lever to disengage the clutch. Whether or not the plates are getting hot it will not have any effect on that.

Should I try to heat up the friction plates evenly to remove tensions ?

No, but you could check them against a flat surface (e.g. a piece of glass) as it's possible , but unlikely, that they may have been warped from new.
If the plates are warped you'd almost certainly find that it wouldn't pull away smoothly from rest.

Or is there any other reason?

As an off-the-wall guess have you re-routed the clutch cable with a sharp bend or so that it's touching the cylinder and getting very hot, thus in some way increasing the friction in the cable?

[Yves.Astein]

Ah I have somehow missed notification about your response. Thanks for helping out Spriddler !

I am not sure anymore, if I had the problem before I replaced the clutch. I replaced it because the clutch was slipping no matter how much I tentioned the clutch springs. But I did also have grinding gearshifts and I believe that was also a reason I changed it. So I on my to do list is, to swap back to the old clutch to see if I have the same problem. What I know for sure is, that the problem was not as bad as now.

I took the clutch apart again, and one thing I recognized was, that when the Clutch plates are removed and I pull on the empty clutch Basket, the basket and the mainshaft in the gearbox has a huge endplay. It moves back and forth about half an Inch. When the clutch is installed, the endplay is gone. No matter if I pull the clutch leaver or not. No play can be noticed…

Concerning your suggestion about the scalloped edges inside the Clutch Basket, that was also a consideration I had. But I discarded that thought, because the problem would only be dependant on the temperature of the Bike. Meaning, that when I ride it, the clutch dose not disengage. And if I let it cool down, it disengages freely. So it is somehow dependant on temperature. The tin case dose feel a bit warm after riding. But not hot. But when reading your message, I did come up with the theory, that the scaloped edges might become a problem in combination of a little heat, with the basket deforming just a little when temperature rises a bit. I don’t if this is to much of a long shot, but maybe Ill just grind of the edges of the Basket a bit, to get rid of the groves…. And see if that helps.

Well I am not shure of the Material of the Slipplates. I bought them at Fecked. It looks flaky dark brownish when oily.

I have a CP gearbox.

I did check the clutch plates to be even on a flat surface. They are not warped. At least at normal temperatures. So I am away from suspecting warping a a cause.

I am relatively sure the clutch is not slipping while driving. If I let the clutch engage at relatively high revs, it kicks in an grabs very abrupt.

I have also tried thinner Oil. SAE20 but it did noch change anything.

I will check the clutch cable as you suggested.

So right now I am at the point where I am suspecting either the friction material to swell up, the scalloped inner clutch basket or the end Play of the Main gearbox shaft….

But first ill try the old clutch again, to narrow down the possibilitys…

Thanks for your Input Spriddler

[dave16mct]

Has the nut on the gearbox mainshaft unscrewed ? I mean the one in the gearbox end of the shaft (in the kickstart case) It holds the kickstart ratchet mechanism in place. There should be only a little endplay.
Dave.

[Yves.Astein]

Ill check the nut. But I am pretty sure I have tightened it well. I am trying to remember, from when I had the gearbox apart, how the endplay of the main shaft is defined. From the Kirstarter side it is the the round socket which is pressed by the nut against the bearing, right ? But how is it defined from the other side ?

[Duncan]

For information, the thread on the ratchet retaining nut 70-X is relived on the ratchet side if a non standard replacement nut has been used it will not fully tighten and give more end float.

[Yves.Astein]

So, I had the time today, to take everything apart and check for the endplay problem of the mainshaft. Thanks to Dave and Duncan I realized, that this is the first thing I need to sort out, before continuing with anything else.

And I found that the ratchet retaining nut 70-X was loose. Thats where my endplay came from. Where that came from, I don’t know. I might have forgotten to tighten it. I have had so many gearbox issues that during the routines of opening and closing the box I might have forgotten.

So now that is sorted out, but that just brings me right to the next headache. And a Question.

When tightening the ratchet retaining nut 70-X the mainshafts becomes quite tight. Meaning hard to turn. So In order to keep the main shaft from being very tight I need to be verry careful to not tighten up the nut to much. Which worries me, that the nut might undo it self after a while.

I then looked at the details and figured out, that the retaining nut with the sleve tube in between presses against the one side of the mainshaft bearing. And from the other side the third gear pushes against the bearing. Which is being pulled against the baring by the edge of the larger diameter of the mainshaft. So when I tighten the ratchet retaining nut to much the third gear gets pressed between the bearing and the mainshaft, hindering the gear to rotate freely on the mainshaft.

Now the question to the experts. Is that how its supposed to be assmbled ? How much torque is normal ?

The hole construction for defining the endplay as I am understanding it now, seams kind of strange to me.
If i dont tighten the nut to let the 3rd gear run freely, then the bearing doesn't get enough pressure from both sides and the mainshaft might be slipping inside the inner part of the bearing instead of the inner bearing turning with the mainshaft. Or am I just making it to complicated ? Forgetting that this is WW2 engineering… So far all the engineering I have seen on our old bikes was simple, but it always made sense. Which I love…

But maybe, the relief on my ratchet retaining nut is just to much, from being tightened to much. ( which I might have done in the past, not knowing how this mainshaft assembly is constructed ) I could turn the nut down a bit on the lathe, reducing the relief a bit. That would ensure that I can tighten the nut enough to stay where it should and still have some endplay.

I have added some pictures for clarity. Hope you guys have the patience to read through all of this. Thanks for taking the time, if you did…

Relief of the retaining nut:


Quite worn out bush flank of third gear due to to much pressure

Side of third gear that rests on kickstarter case bearing. The other side has the flank as shown above.


Thanks for any help. Unfortunately I have a long odyssey of problems that I have been fixing on this bike. The former owner tried a restauration which caused many things to be assembled wrong. ( It was a huge mess) Which I now am trying to figure out. I have redone the hole restaration including paint job and I was able to reduce the problems down to the clutch and and gear shifting issues. So almost there…. I bought the bike for a good price as a discontinued Restauration but I wasn't expecting such a huge mess. But I am enjoying to sort it out

Cheers Yves

[Duncan]

It may just be the scale of he photo but it looks like your nut has worn where it meets the mainshaft, the nut should tighten on the mainshaft with the wear it will bear on the ratchet reducing the endfloat. it could be worth measuring the step and seeing if that would give you enough endfloat. If so either a new nut or relieving the spacer tube for the kickstart ratchet by the same amount could be a remedy.

[Yves.Astein]

Thanks for providing certainty Duncan. Thats exactly what I needed to know. I might just turn down the face of the nut a bit.

And then we will see if the right endfloat will also cure the clutch problem. I will post the results…

[Yves.Astein]

Just to complete the story. Problem is solved. I faced the ratchet fixing nut on the lathe and shimmed the endplay between the nut and the ratchet. Worked like a charm, and the clutch is now fully disengaging.

Thanks for the Help !