Troubleshooting a JAP Special

[Rockburner]

Not much to report today.

Refitted the timing chain cover and the pumps, after cleaning out the oil feed tube with some very handy little brushes I have.


Currently waiting for this nut to turn up.


And refitted the primary chain cover



Obviously all that took me about 2 hours of faffing about and dithering, as per usual

I reckon that, in a pinch, I now probably could strip and rebuild the engine over night.... if I had to.... but it's not something I'm going to try.

Fingers crossed that nut will turn up tomorrow and I can get out for a spin and see how it's behaving after the clutch rebuild.  I'm fully aware that it's down on power and compression, but I want to actually ride the thing a bit more before stripping it down again, hey - it'll keep me busy over winter again.

[Rockburner]

I took it out for a spin this evening, and it's running fine, apart from the fact that the damned clutch is slipping at anything over 50mph.

I suspect it's just not setup correctly so will have a play this evening and fingers crossed it'll be good for the weekend.

In good news, it's nigh on oil tight now, apart from that one cover i haven't tried to seal, the timing chain cover.

Incidentally, if anyone is at a loose end and is near the South Coast on Saturday, there's a classic vehicles meet in Selsey, just a suggestion.

.... Later...

So, I think the clutch was indeed badly setup - there was zero play in the lever in the gearbox when I looked this evening.  So I've pulled it apart again, because I was kinda pondering if the plates were badly worn...

however... according to the details I've found: the friction plates should be 0.138" thick, the plain plates 0.080" and the single-sider on the outside (which the pressure plate pushes against) should be 0.110".

I measured them all:


The plates I have are :
Plain plates: 0.080", 0.082", 0.080", 0.082", so they're fine.
The single-sider is 0.111", so it's fine
and the Friction plates are : 0.171", 0.158", 0.172", 0.170"  So, err they're all too thick.


Which makes no sense. (to me at least).  By all rights the thing should be dragging like crazy, not slipping!  :wtf:

I also checked them for flatness on the flatest thing I've got


One or two had a "little" bit of rocking movement. I'll look into how much new plates are and think about it.

SO I did the only thing I can do for tonight....
I buttoned it all up again, and reset it again, trying to follow the manual's instructions as best I could


I think clutch setup is a bit of a black art to be honest....

Oh, and it looks like I was being a bit presumptious about the oil tightness....
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Hey ho, it's better than it was!

[chaterlea25]

Hi,
Looking at the photos of the clutch centre hub it can be seen that the splines have been ground away, this is why the clutch is getting so close to the final drive chain!
It may have been a bodge to get the primary chain lined up to the engine ??

John

[Rockburner]

Hi,
Looking at the photos of the clutch centre hub it can be seen that the splines have been ground away, this is why the clutch is getting so close to the final drive chain!
It may have been a bodge to get the primary chain lined up to the engine ??

John

That's possible, the primary chain run is very much to the outer limit of the front sprocket carrier. 

That doesn't explain the washer that was there, pushing the clutch out futher though! 

It could be that the ground away material was either from another fitment on another bike, or it was an experiment that didn't work out.

I have a feeling that the washer was there so that the clutch could "float" on the shaft a little - the clutch hub nut was NOT very tight when I undid it. 

When I tried to do it up tight, with the washer in place, the washer was pushed hard against the outer main shaft of the gearbox, locking the 2 gearbox shafts together.

I've done the clutch up tight on it's shaft, and while the drive chain is very close to the back of the clutch, there IS clearance.  I'm going to be scouring the autojumbles for another clutch I think, or parts thereof.

[Rockburner]

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..."

[Rex]

It might be grandma's eggs, but have you tried cleaning the friction plates in a solvent like celly thinners?

[cardan]

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

[Rockburner]

What I actually did, was to put them through a ultrasonic session, then a good brass brushing.

After taking to a subject matter expert today at the local show, I think the washer that I mentioned is supposed to be in there to get the gaps right, so I'm going to strip the clutch down again, probably soak the plates in petrol for a bit, then reassemble with the washer. Apparently it's supposed to sit on the OUTER shaft, ie the gearbox output shaft, but I think I had it on the inner shaft which is why it was binding up the gearbox when the clutch centre nut was done up tight.

I'm going to need to reduce the outer diameter of the washer though, so it doesn't foul the clutch stud nuts on the back of the clutch.

[Rockburner]

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!