Clutch cover with hole worn through it

[Degsy]

Greetings All

I am in the final stages of my rebuild on the derelict A7 non runner I bought at the beginning of the year. I have rebuilt the engine and gearbox and I am at the point of putting the primary drive back on.
 
The bike was a non runner, and the clutch slipped on kick over due to a seized piston and a clutch full of oil.   
You can see (photos below) the cover has worn through and let the oil inside the clutch. 

It looks like the wear was caused by the ends of the clutch spring adjusting nuts rubbing on the clutch cover, but why would this happen?  Could it have been setup with too much travel on the clutch pushrod and then when disengaging the clutch is pushed up against the cover?

The clutch thrust washer does not look worn.

When I pulled the clutch off the drive shaft I noticed the two halves of the Main shaft Split Washer (Part number) 67-3251 in the bottom of the primary drive case, but I think they may have dropped down there as I slide the clutch off its shaft.

I have sourced on ebay another clutch cover (see Photo), but it looks different. 

My clutch cover has a step into a 5mm deeper section in the centre, I cannot find any images or diagrams of a clutch cover that looks like this.  Are there any BSA clutch covers with this step or is it caused by the spinning clutch pressing on the dome?  Maybe a bit like the metal bowl spinning technique on a lathe!

So:
What do you think caused this clutch cover wear?

Is the shape of my clutch cover a genuine BSA design or just the result of the wear pattern?

I have heard the clutch will work OK bathed in oil and without a cover, is this true?

Grateful for any thoughts

Thanks

Degsy

[a10 gf]

I have sourced on ebay another clutch cover (see Photo), but it looks different. 

The ebay one is the right one.

But why would they have fitted this strange thing that came with the bike? Non-original clutch parts needing some extra space which the cover may provide ?

A photo of all clutch parts > https://www.a7a10.net/BSA/techpics/clutch1.jpg

[Greybeard]

The cover does two things. It prevents lots of oil getting on the plates. The cover also reinforces the clutch basket.

[Swarfcut]

Degsy. Compared to later designs the arrangement for locking the spring adjustment on the Plunger Clutch is crude. Originally the spring cups and brass adjusters had raised pips to snag on the cut ends of the springs. Over time,  adjustment  wears these away. Pattern parts may not even have them, so very little to stop the adjusters unscrewing and machining the cover.
   Thread lock on the adjusters works fine these days.

       My bike was missing the cover and also the split collar you found. My thrust washer was running on the oilseal rivet heads.

    One of the plain plates is somewhat thicker than the rest, this goes into the basket first to support the spring load. With an unknown history, never take anything to be correct. The number of plates might have been someone's best guess. The oil level only needs to kiss the chain, plenty on the forum about the various methods folks use in the strive for perfection. Too much oil was always a problem, the thinking was that more was better. it ain't so.  In earlier times, swapping the friction material for cork inserts would allow the clutch to run in oil, of course a leaking primary case ran the risk of burning the corks when it ran dry, so you took your choice.
   The cover is a plain, domed pressing. Nothing special, and a smear of silicone will help seal the gasket.

 I see you have a modern cush nut.  I thought these were only made to suit the later S/A models. The original Plunger version has an extended nose and substituting a flat faced S/A type  without an additional homespun spacer will compress the cush spring too much (in my estimation) and restrict the  plunger cush lift to nothing when the nut tightens against the drive sleeve. The two designs have detail differences, and to use the flat faced nut requires the S/A spring and sliding S/A cush member, which is a poor match with the duplex sprocket cush ramp profile on the parts I have to hand. In addition the S/A cush member requires a reduction in diameter  of a couple of mm to fit the duplex sprocket.

 Nice clear date stamp, rest of the cases look good, with not the usual evidence of ham fisted abuse.

 Swarfy.

[Degsy]

Hi all

I don't think there are any non-original parts in the clutch but I'll take a closer look.

I should know by now not to assume anything with this bike, as a Bobber that seems to have been put together from spare parts, it has thrown up some surprises.  I will check the make up of the clutch plates and bits.

Good point about the cover adding strength, I will not plan on leaving it off.

Swarfy - yes I  a bit confused that the cush drive looked different, thanks for confirming what it is.  I will have a look at how it goes together and tightens down.

Cheers

Degsy


Degsy

[muskrat]

G'day Degsy.
Just another observation. The lockwire on the nuts should be in a figure 8. The way it is they can still loosen.
The cover is to keep most of the oil out but over time a fair bit gets in, especially the early (pre 53) plungers without an oil seal on the crank. If left for a while and she wet sumps the primary fills with engine oil (mine does in a matter of weeks  ).
Cheers

[Jules]

Interesting that plunger models have the clutch cover but s/a doesn't, why's that?? it would seem to be a good idea wrt oil contamination of the plates....

[Degsy]

Hello all

I have gone over the clutch again and all parts appear to be standard.

Swarfy - Impressed by your detailed knowledge, I had a look at the brass cups and spring adjusters and yes they are worn to the point of not having any holding effect on the spring adjuster nuts unwinding.

I have now come to the conclusion that what appears to be an unusual OEM clutch cover with a deeper centre section is in fact the result of the spring adjusters unwinding and pressing on the spinning clutch cover.  This was gradually pushing out the point of contact with the clutch cover and eventually wearing a hole through it.

This might seem hard to believe especially as only one of the brass spring adjusters shows a little wear from contact.  But if you are familiar with the technique of creating a bowl from a metal disk on a lathe using “Spinning” (check it out on Youtube), it is surprising how little single point force is needed to distort a disk into a bowl when it is spinning.

Thanks for confirming that the cover is not a standard part and that unwinding adjusters is my problem.  Application of Loctite should solve this on reassembly.

Muskrat – Thanks for spotting the locking wire error I’ll sort that when things go back together.  Regarding the oil in clutch issue, It is odd that as Jules points out that the S/A models have no cover so must be exposed to oil, although the clutch internals are different from the Plunger models.

Yes Swarfy, the date stamp is clear on the inside of the primary drive case and is also stamped outside on the engine.  So in nine days it will be my engine’s 70th Birthday!  I must think of a way to celebrate,

Swarfy I will be back with a question about my Cush drive.

Thanks

Degsy

[RichardL]

This metal spinning result is interesting. It seems it all had to occur only when in gear and with the clutch disengaged. Amazing it never made enough noise to attract attention. After all, the cover is intended to keep oil out, so, little lubrication against a screech. "Hey I wonder what that wild noise is that's coming from the primary while I'm stopped at traffic lights.?

Richard L.

[Degsy]

Hi Richard

back in January, I bought this bike as a non runner that had been laid up out in a back yard for a few years, I do wonder what it sounded like, it was not without other problems, when I stripped it down there were problems with the roller bearing conversion causing oil starvation, it looked like the engine had seized and the big end bearings showed excessive wear.

Anyway, all sorted now I hope.

Degsy

[Degsy]

Hi Swarfy

I cannot get the personal messaging to add photos so I am replying to your Cush drive comments through this thread....

Swarfy -  Thanks for the explanation but I'll need to get back in the garage with the bike and cush drive tomorrow before I can understand it properly, in the meantime here are a couple of photos I took yesterday.

As I understand it this end nut was an aftermarket upgrade that allows the use of a socket and torque wrench instead of a 'C' Spanner which is difficult to torque down properly.  I see  SRM currently sell an example of this.

The gap between the uncompressed spring is 6.3mm. Tomorrow I will try it on the drive shaft to see how it looks.

Thanks for your comments

Degsy

[

[Swarfcut]

 Degsy. Yes, Personal Emails don't have provision for picture files.

 You look to have the correct Plunger sliding member and drive sleeve. Second picture shows the sliding member and drive sleeve almost level, as they should be. You can see that if that later nut tightens down onto the sleeve, the cush will be locked solid. Leaving a gap for the sliding member to move means the drive side main bearing is not pressed to the crank, the result being movement, wear and disintegration of  the crankshaft shims. To use that nut requires a spacer, made to pass inside the sliding member, allowing the cush to move and the nut to load the drive sleeve against the bearing inner race.

 More on my Cush Drive Conundrum post.

 Swarfy.

[Degsy]

Hi Swarfy

Yes you were right this wrong nut will just lock up the Cush Drive (see photo).

Rather than a spacer I think I will go back to the original design of nut  (see photo part number 67-2054) , it appears to have a step to allow the  sleeve to move.

This would mean going back to a ‘C’ Spanner to torque it down but it would allow the use of the a split pin through the drive shaft hole to lock the nut in place. 

Cheers
Degsy

[berger]

don't know much about plungy's but that cush bit looks more swinging arm than plunger, someone will be along to confirm or not

[Swarfcut]

 Bergs. The clincher is the depth of the collar from the "flat end".  S/A it's around 10/13mm, Plunger is deeper, 21/22mm. S/A cush peaks are also too far apart (51mm compared to 49mm on the plunger)  to bottom inside the duplex sprocket. Finally the splines are different, S/A are shallower but spacings and number of splines is the same.

 Degsy, get measuring, looks fine to me, but then again Specsavers was closed last time I went.... Forget a puny C Spanner, make a custom peg jobbie to show the nut what 60 plus Ft/Lbs feels like. New pattern nuts are all made to the same mediocre too tight on the thread standard. Even a butchered used one has the assurance that it fitted in the factory. Split pin won't lock the nut, just prevents a similar clutch cover hole appearing in the primary cover.
 
  Those clutch cover pix are well worth adding to the Great Mechanical Disasters thread.

 Swarfy.