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Earliest Jubilee Clutch.

Submitted by peter_holland1 on Sat, 10/12/2022
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Light Twins

Very recently there was a post here asking about replacement clutch spring studs for the early Jubilee clutch.

This clutch can be identified by a small spline and a hardened ring in the back of the clutch centre.

I have been known to be wrong but ...

When dismantled this clutch backing plate will be unbonded. No friction material. Unique to the earliest Jubilee clutch.

The race plate is unique to this clutch. As is the clutch centre.

This clutch will be something similar to the exploded clutch view in later lightweight parts lists. I believe the clutch shown in the diagram is a very early lightweight Norton clutch. Observe in the diagram no friction pads on the clutch backing plate. AMC never re-drew the exploded diagram to keep up with improvements.

I would advise anyone dealing with one of these early clutches to be very aware that they have many different components and operate in a slightly different way to the 1960 onward lightweight clutches. A bit of a weak design and probably unable to handle Navigator full torque.

Attachments
earliest LW clutch centre -r.JPG
Earliest LW mainshaft (2).JPG
Later clutch - larger spline .JPG

Submitted by peter_holland1 on Sat, 10/12/2022

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Raceplate pictures showing differences.

I am afraid I can't definitively say which clutch spring studs are correct for this early clutch, but if your replace a bent stud with another of the same design, all will be well.

When the clutch stud securing nuts are tightened the clutch, and no plates fitted, the clutch centre should be free to rotate within the clutch basket. In the early clutch, even when loading the basket axially towards the mainshaft.

On the later clutch the backplate has bonded pads and you will feel the drag as you push the basket towards the mainshaft.

Good luck Ulrich

Peter

Attachments
Raceplate depth as roller.JPG
Raceplate depth roller plus cage.JPG

Submitted by ulrich_hoffmann on Sun, 11/12/2022

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Hello Peter,

I accidently deleted the post, I hit the wrong button.

Here are the pics of my clutch:

This is with the new studs in it.

I guess it is the small spline, don´t have it at hand to measure the diameter.

My Jubilee is No 340 of the third batch ever built.

clutch rear

Differences between old an new clutch spring studs :

the rear part of the original studs is longer.

The new studs do not lock into the race plates with those flat sides.

I also had to file a bit off to make them go into the slots that is why the left stud looks "used".

You can also see the bend threads for the spring adjusters on the old one.

spring studs

Plan A: Find the correct studs ( AMC, Francis Barnett, AJS whatsoever)

Plan B: straighten the old studs and recut the threads with a whitworth cutter which is very easy to find in Germany...

Plan C: I know somebody with a lathe.....

 

 

Submitted by stanley_pyke on Sun, 11/12/2022

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Hi Uli,

I have been having a look online and found three AMC numbers but no sizes to them (see below). But also found this

British Only Austria

https://www.vintage-motorcycle.com/en/parts/ajs-matchless?title=&art_nr=&field_manufacturer_target_id=All&sort_by=title&sort_order=ASC&items_per_page=100&page=3

near the bottom (page 4)

Stud AMC Clutch 67.4mm. 2.21/32" Article number 04-0384. 040384. 04.0384

or  got to  https://www.vintage-motorcycle.com/en and search for 040384

Could be worth asking for more size details

The Three other studs I found are

043189 for all 7 plate clutches

043174 for 9 plate with simplex sprocket

043338  for 9 plate with duplex sprocket

Hope this helps and good luck, Stan

 

Submitted by peter_holland1 on Sun, 11/12/2022

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I can see you have the earliest Jubilee clutch with smallest spline on mainshaft. There is a hardened ring let into the back of the clutch centre. Your ring shows some marks from the mainshaft splines despite being hardened. Not significant.

My observation of lightweight clutches in general:

Bent spring studs, scarring on the outside of spring housings, and worn/disintegrated/missing shock absorber rubbers seem to go hand in hand.

I might try to straighten the studs before getting specials made.

Best wishes.       Peter 

 

Submitted by gary_turner on Mon, 12/12/2022

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Hiya Peter/All - Annoyingly I have misplaced the collar that you identify in your earliest LW clutch centre and main shaft pics. In case I cannot locate it. Do you have the dimensions please? or alternatively a part number please?

Regards

Gary

Submitted by peter_fairbank on Fri, 16/12/2022

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Hi. Gary.

There are two clutch studs available in NOC Spares 043441 - 65 mm. and 21481 - 68 mm in length hope this helps.

Peter F.

Submitted by ulrich_hoffmann on Sat, 17/12/2022

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Thanks for all your hints and help!

On Wednesday afternoon my friend Jürgen and me  managed to straighten the original studs and we recut the threads. We used the original spring adjuster nuts because we found out on the new ones from NOC spares the inner thread was bored and cut at an angle so the nut did not sit square on the stud.

clutch

Submitted by peter_holland1 on Sat, 17/12/2022

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Hi Uli,

I had the same problem with replacement studs from NOC spares about 3 years ago. On all 3 studs the inner threads were cut at an angle and were un-useable. Guess what, after complaining I straightened my old ones.

Well done with the build.

See you are using original steel chain tensioner. Careful. Norton replaced with a nylon type because owners were setting tension in primary too tight to allow for expansion of aluminium crankcases at running temperatures. Steel chain expanded less than centre distance between crankshaft and gearbox grew.

The later nylon block gets chewed by the chain if things get too tight, and the chain and bearings survive.

Obviously one of the problems that emerged as AMC went to unit construction.

Peter 

 


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