classic motorcycle forum

I think you're barking up the wrong tree with that worn clutch centre; if you think it's an issue then simply take a 12" !"£%^% to it and smooth it out. The worst that will happen is that it would rattle slightly more when the clutch is pulled. Hardly a concern.
Usually they're worn much more than that, and the main symptom is a dragging clutch leading to crunchy gear engagement when pulling away.
Don't really see how the minimal wear you have there will/would cause clutch slippage within 50 miles or so.
£330 quid is a bit much for suck it and see diagnostics, too. I'd be looking at plates, springs and something amiss with the assembly first.

Well, this is the dilemma. I am struggling to find anything "else" that could be wrong.  The plates aren't too worn, the assembly "seems" ok, there was sufficient play in the push rod that I'm sure it wasn't causing slippage. The springs seem strong enough.... What else is there? This is the first time I've tried to get a Norton clutch working, and I'm not familiar with clutches in general anyway, so any specific ideas will be welcome.

Oh, and a 12 inch what?

Last night I made my (poor) excuses and got out into the shed again.

I pulled the clutch apart and put the plates into some petrol:



While I tried to get my head around this flaming washer.  The local JAP man, who races JAPs in cars and bikes, and has a Manx engined F500 car, which uses a Norton gearbox and clutch, told me that there SHOULD be a washer between the clutch and the gearbox, and (after some detailed discussion) imparted the knowledge that is should be sittingon the OUTER shaft, not the INNER shaft - the gearbox output and input shafts respectively.

NB: the gearbox input shaft rotates INSIDE the output shaft (they rotate in the same direction, but at different speeds).

This mystical washer, according to local JAP man, should sit on the OUTPUT shaft and essentially serves (it appears) to ensure an offset between the clutch and the gearbox output sprocket.

The thing is... this makes no sense to me at all.  Because the clutch has a splined fitting on the end of the input shaft, and that fitting is both tapered, and has a solid stop.  If you do the clutch up tight (without the washer), there IS an enforced clearance between the back of the clutch, and the end of the output shaft.  I simply can't see the need for a washer, the clutch can't bind to the end of the output shaft.

... and besides - if the clutch was NOT supposed to go up tight on that taper, and wedge itself in place under the nut.... WHY would everyone be selling a specialist "Clutch Removal Tool" specifically for pulling the damned clutch OFF that taper??  :wtf:

I pulled the clutch back plate off and fitted the body of the clutch by itself onto the gearbox input shaft:


It's not that easy to see - but the washer is free to rotate with the clutch body tightly screwed on:
https://youtu.be/yYCOc3h9h3A

So - why do I need a washer there???


When the clutch back plate is fitted, and the stud nuts are in place - that washer fouls the stud nuts (it's worn them away in part - as you'll see later - which can't be right).

I cleaned up the studs and the nuts :


Took the race plate and the roller bearings out (yes they went everywhere, and yes I swore a lot, and yes I lost one .... found it again eventually...)



The rubbers still won't come out - but at least I was able to have a sort of evaluation of them - they seem pretty solid still, there's some debris in there  - but not a lot really.


Gave the studs a good brassing: (I gave everything a good brassing!)


Failed to count the roller pins propertly ....  twice...



Back plate, race plate and main body



In all honest - I think this is the real problem:


The dogs on the clutch body: which is where the friction plates act* are battered quite badly.



* : power from the engine comes into the clutch via the "plain" chainwheel plate / basket. 
The other "plain" plates are roated because they interlace with the walls of the basket
So - the "plain" plates are the "driving" plates, carrying the torque from the engine
The Friction plates are pushed against the Plain plates by the springs
The Friction plates are then rotated by that interaction, and
the Friction plates then bear on the clutch body in order to transfer the torque from the engine into the cush-drive rubbers.
The Rubbers then absorb some of that "impact" before passing the torque to the spider in the centre of the clutch,
The Spider has a splined/tapered core which slides onto the end of the gearbox input shaft.

Thus the engine torque is transferred to the gearbox (with some minor losses)

So - the battering that the clutch body gets: would tend to happen when the clutch is "engaged" and the throttle is opened hard and quickly.

Hmmmmmmm.


I carried on with reassembling the clutch body anyway.



These are the battered stud nuts on the back plate, they're a git to work on because they're so flat, knackered, and the back plate has dished areas so getting the spanner on them is very hard (I don't have a 6-sided socket in that size). You can see where the washer has worn away the flats - this is another reason why I don't think the washer should be there.


With the clutch body assembled, and the pressure plate installed:


In this assembly: the pressure plate is NOT hard up against the outer face of the clutch body.  The spring cups HAVE bottomed out, but the plate rattles about (the clearance is less than a millimeter I'd hazard, but it is there)

This is the washer in question sitting on the input shaft... it's NOT large enough to go over the output shaft


Here you can clearly see the output shaft and the input shaft inside it. The pimple sticking out of the input shaft is the clutch push rod which pushes against the underside of the pressure plate (there's a large grub screw in the centre of the pressure plate to allow adjustment: the push rod needs to have enough space to accommodate thermal expansion and have some free play, otherwise the pressure is taken off the plates and you get slippage).



I still don't "get" the washer at all, and I am very concerned that the main clutch body is beyond usage due to those battered dogs/splines.  A new one is around £330 (https://andover-norton.co.uk/en/shop-details-2/15111/clutch-centre-hardended-and-ground), and that would likely entail new plates (~£15 each: 9 of, ) etc etc ..... and you're building up to nigh on new clutch territory.... which is around £830-£950 or so....



Or spend the next 6 months wandering around autojumbles hoping to get lucky, and/or dealing with 2nd hand ebayers and who knows what will turn up in the post....



hmmmm

Current plan is to get a second opinion on the clutch body by taking the dissassembled clutch down to Selsey; and not get too far ahead of myself in the meantime.  The Selsey JAP guy did tell me on Saturday that he spent £400 on something and it was the best £400 he ever spent, but I didn't quite catch what it was that he'd bought, I just know it was something for the clutch!

What confuses me about the worn splines on the clutch body is: that can't have happened suddenly over the first 50 miles or so since I got the engine back in the bike ... it must be pre-existing wear (I'd imagine it would take thousands of miles to do that sort of damage), so why did the clutch only start slipping about 30 or so miles ago?  It's very very obvious when the clutch is slipping, because the kick-start torque goes through the clutch - if it's slipping, the engine will NOT turn over!

And/or boiling them in a water + strong detergent?

Slacked off work this afternoon to take the bike out for another quick spin.

and there was a lot of spinning.... the damned clutch is STILL slipping.  It's obvious in all gears, in first it won't "bite" above a certain engine rev-speed, and in the other gears it simply won't go above 50mph.

So I dragged it's sorry ass back to the shed and had another look.

I screwed the springs in a couple more turns, and made sure they seemed to be "balanced" : ie the pressure plate lifts equally all the way around (as best I could)


I confirmed that there was enough slack in the push-rod linkage, there's plenty.


And then buttoned it back up.  I'm taking it down to Selsey tomorrow whatever (well - unless it pisses it down...), and then we'll see after that.  I think I now know roughly what the clutch "is" (ie which type, and what plates I would need to buy), but there's still a few details I can't tie down, so more research to do. 
I'll look into new plates and new springs, they're the only things that should need replacing.

In the meantime.. the next little project is going to be stripping down the Pilgrim Pump to replace the gaskets: I'm pretty sure that the gasket under this cover plate has gone - there's a definite "snail-trail" coming from it.




"These things are sent to try us..."

This is what rusty ones look like - in the same place.

Leon