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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on September 12, 2026, 08:49:16 PM »
So, I did a  bit more research and bought a few bits from RGMNorton.


New push rod, longer adjuster screw, and a fancy new clutch lock nut with a built in oil seal around the push rod.


So this evening there was a blur of frenetic activity in the workshop!

This is the original push rod in place with the cable adjusters loosened off


This is the difference in length from the old push rod to the new one!



And this is new push rod in place!


It's a little too long tbh! :lol:


So I took some measurements to figure out how much I needed to take off it.








I think I'd need to take roughly half an inch off it too bring it down to a length where the pressure plate adjuster nut is usable.

So, in the spirit of investigating all options: I put the old rod back in and tried the longer adjuster screw.
Not bad!


That was with the adjuster pushed up against the end of the rod, with it retreated slightly to allow a gap, there's a decent amount of thread left for the lock nut


This is the play on the actuating lever:



I'm actually quite lucky with this bike because when I'm adjusting the clutch cable and lever, I can reach through the frame and get a finger onto the actuating lever so I can actually feel the movement of the push rod as the adjuster screw contacts it, so it's easy to get the adjuster screw "just" touching the rod, then back it off. If it was a normal Norton, there'd be a whacking great oil tank under the seat getting in the way. :D

I then continued putting everything back together


This is the "play" I ended up with on the clutch cable adjuster


Remembered to put the inspection cover back on


Then...errr ... there was just enough light left to take it out for 10 minutes!
:D

Very very good run out! The clutch is behaving perfectly now! :D
I figured it was good when the bike was spinning up in the gravel, and pulling away in first felt like a modern bike!

First gear is still a pain to get into at standstill, but tbh I think a lot of that is the rear-sets, on the move the gear change is smooth as silk, up and down. :D


The only fly in the ointment was that the clutch lever play seemed to be opening up as I headed home,


So I need to pull the cover off again and see what's causing that. Possibilities are: the adjuster has loosened off, which is a simple fix.... Or the clutch main nut is loose, which is rather more scary!

Long term, I may cut down that new push rod and use the fancy new clutch nut, but for now the longer adjuster nut has made all the difference and seems to have solved the immediate issue. We'll have to see if the gearbox oil still contaminates the clutch and it that causes problems.

I did consider the fix of putting a bearing into the push rod, but tbh, I figured a longer adjusting screw was going to be the easiest fix, second only to a longer push rod, which may still happen eventually.

But it's all good otherwise, and I'm a happy bunny! :D
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by cardan on September 08, 2026, 12:45:14 AM »
I'm with Rex on this one - don't overthink it. 1/2-20 on a British bike will be BSCy, an alternate to the usual 1/2-26. UNF is also 1/2-20 but with a slightly different thread form.

Leon
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rex on September 07, 2026, 09:41:47 PM »
Cut the pushrod somewhere on it's length and put a 1/4" clutch roller in the middle. A bit of grease and good to go.
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on September 07, 2026, 07:02:09 PM »
did some measuring tonight to figure out what's going on....

the new pressure plate adjuster is 5/8" long (when measured from the bottom of the screwdriver slot! )


From some reading I've done... there's actually a long one supposedly available at 7/8" length.  Hmmm.

It's a 20tpi thread


And it measures at 0.491" diameter, which is as close to 1/2" as makes no odds (to me).  BSC??

I also checked the clutch lever pivot distance - it's supposed to be 7/8" to give the correct leverage, and it seems to be correct.


The Push rod however, is a bit of a mystery.
It's a 6mm diameter (exactly), so it's a "modern" one.
the length though.. is 8 15/16"  (228mm). 


Which is... err... rather shorter than anything I've so far found.
Supposedly the nominal length is 9 11/16" or 9 1/2", or 9.752, or 9.68", or 9.80"....

I think it depends on what people seem to have found in their box!

But, all those measurements are 9" +  So my push rod would indeed appear to be too short, so I'll look into a replacement I think, just to be sure that the rod is properly long enough to protrude enough from the tube it lives in. 

I also spent some time fiddling with the actuator lever trying to figure out if it's gone weird.. but I can't make it out - there's a weird "double-movement" that I'm feeling when I try it with my finger on the end of the push rod.  hmmmm.. odd. (but possibly correct?)

more thinking required.
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by cardan on September 07, 2026, 02:23:21 PM »
There's nothing magic about the push rod itself: you can make a new one with the correct length from silver steel, with the ends hardened (heat to cherry red and quench in oil). Usually if there's a ball, the push rod is in two pieces and the ball is in the middle - it will try to fall out is it goes at either end of a one-piece rod.

Leon
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on September 07, 2026, 10:37:07 AM »
I managed to get an hour in the shed on Sunday, and the rest of the clutch bits had turned up from Andover Norton.

New, (straight!) studs


Adjuster screw and locknut


The first thing in the clutch assembly (after the rubbers and the outer plate) is a tiny bit of "anti-centrifugal grease" on the clutch bearing.... I couldn't find any information on what constitutes "anti-centrifugal grease", so I dug out the high-temp lube I use for brake pads etc.  I'm going to use an extremely small amount, so I figure that all it needs to be is capable of withstanding high temps and not flinging.

The bearing "inner" is the outer diameter of this plate:


Told you I wasn't going to use much.... (actually I used twice that...)


Bearing half-assembled


Studs into the clutch body: they're keyed to semi-squared holes in the bearing race plate so they don't rotate.


Assemble the rest of the body, and don't drop it....




BUGGER!


Try again.
Lastly fit the stud nuts on the back


Clutch body onto gearbox layshaft with washer, lockwasher and big nut


Big nut is the same size as a spark-plug


Again, without having the proper clutch holding tool, I have to resort to using the rear brake to lock the layshaft (via the final drive and gearbox)


I bet myself I could get the stack on in one go.... YAY!


Then I freed off the clutch cable as far as it would possibly go to give myself plenty of slack to work with while getting the setup right.  Ideally, the lever in the gearbox needs to be "over-center" so that the cable pulling it has plenty of room to work.  That means the lever need to be as far away from the gearbox inner as you can get it.


Lots of slack...


Even more slack - from freeing off the handlebar-lever adjuster


The push rod is now a "long" way into the layshaft when "at rest"


And the lever is as far "out" as it will go (probably too far tbh!)


Then fit the pressure plate, spring cups, springs, spring nuts.  The advice is to screw the spring nuts down until they are "flush"


What is supposed to happen next is that you adjust the screw on the pressure plate and the clutch cable adjusters so that although you have a bit of slack (either 1 or 1/2 turns back on the pressure-plate adjuster: advice varies) to allow for thermal variation, and the clutch lever has a nice pressure on the clutch.  Bearing in mind that the push-rod lever needs to be "over-center" and not fouling the inspection cover.

However... to get any where near that state, I had to screw the adjuster screw in so far, that the lock-nut wasn't going to work: even this wasn't engaging the push-rod.


Obviously, with a pressure plate that's about 1/4" deeper than I had before... I need more length in the rod (ooer), or some other way of taking up that gap in the mechanism.

At least enough to give the locknut a fighting chance... It should look like this.


Obviously it took me a few minutes to puzzle that out though, I thought I'd gone mad.

The last thing I did was pull the push-rod out again... and it's covered in oil.


Which confuses the hell out of me - I'm sure I put it back in clean, and the oil is fresh clean stuff, (obviously, since I changed the oil) so - given that the layshaft tube is much higher than the oil-level in the gearbox and the mods I've done are supposed to stop this... the only conclusion is that my mods didn't work. BAH!

I may look at fitting a larger diameter breather , or possibly just drilling out the jet that's fitted (off the gearbox, obvs).  but the sheer amount of oil on the layshaft is really confusing to me.  The way the oil supposedly gets in there is a "oil-mist" when the box is hot and the internal pressure pushes the air/oil mist in there out of whatever exits it can find: the clutch cable is one exit, the push-rod-tube is another, and the blow-hole on the original inspection cover is a third. The idea of fitting the extra breather is to increase the number of exits and so reduce the propensity of the oil-mist to  get where it shouldn't (down the push-rod-tube!).

These clutches do normally, ie, by design, run in an oil bath (the original primary cases on Nortons contain an amount of oil (Not sure huow much, and it seems ATF is preferred, makes sense), mainly to lube the primary chain, so any gearbox oil lost down the push-rod-tube probably isn't really noticeable.  But I'm running this clutch dry (although I think it's got plates that "should" be ok runing wet), so the oil seepage is a lot more noticable, and I was thinking that it may have been what caused the slipping - although I'm beginning to wonder if the oil seepage was just incidental and not the main cause of the slippage.


So, steps in the right direction, and yet more choices to make.

Regarding the push-rod, I'm thinking that tbh, the easiest way to fix this is going to be a longer pressure-plate adjuster screw, so I'll be taking measurements and seeing what I need to find to achieve that.   
Oddly - ther appears to be 2 options for this, but I've only found this reference in one place (so far).
Quote
040360: Adjuster, in press. plate. All. Short (5/8”).
061179: Adjuster, in press. plate. Long (7/8”) Norvil, Dom, Comm
So - I'll look into that.

Some advice I've read is to put a 1/4" ball-bearing down the tube as a "spacer/extender", and I may look into that if I can find one in all the junk I've got.  There's already a ball-bearing as part of the push-rod-lever :


Again - an option.

So, plenty to keep me busy....
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on September 03, 2026, 05:57:54 PM »
The new clutch hub turned up today so I went and did some fiddling!


With the clutch you perves!


New hub looks the part:


Slots into the stack nicely


This should be fun....


C-spanner, gearbox in first, brake locked on....


All in with remarkably little swearing! Many thanks to iansoady suggested the C-spanner method.


Then I did some tinkering and playing about with fitting things - I bolted up the back plate and the race-plate so that I could be sure the central spider was in place fully. (sorry, no pics).

I've discovered that 2 of the studs are bent, so I'm getting new ones while the clutch is in pieces and I can fit them quickly.  But the old ones sufficed for a reassembly test.

Then I turned my attention to the spring cups.  I think with the deeper pressure plate they're not going to be bottoming out, but they could do with a clean up and I figured out a way to do it.

Behold... scrap.


And yet... assembled in the right order... this spring cup is ready for a spiffing.


Who needs a lathe?


Take it easy, and nothing will be damaged...


Bit of P600 to smooth it off.


Pre-spiffed, spiffed, and desperatly needing a spiff


Good enough for me.



Probably not going to make one iota of performance difference, but it was satisfying to do. :)



and I just nearly caused myself a panic attack by thinking that I'd got the rubbers in the wrong way around... but comparing this view of the BACK(inside) of the clutch body:


With this view of the FRONT(outside) of the body:


You can see that the rubbers are in opposing positions.... as you would expect!

Phew!
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British Bikes / Re: After the rides done, wheres the best place to find someone whos just as keen on classic bikesan
« Last post by Rex on September 02, 2026, 09:30:13 AM »
There's the local Spam enthusiasts club; you might find that interesting.
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British Bikes / Re: Troubleshooting a JAP Special
« Last post by Rockburner on September 01, 2026, 06:23:04 PM »
Still waiting for the new clutch hub to arrive, but some other bits turned up.

New pressure plate is 0.915" "high" so a good 0.2" higher than the old one, should be good.


new rubbers - they're "shorter" than the originals, by about 5mm~ish but I can't really see a problem there, they should still do the job, they're captured on both "ends" of the clutch body so it should be fine.


I also got some new stud nuts so spent an hour or so just spinning a die up and down the stud threads to clean them up.  If you can spin a die down a thread just using your fingers then you're not going to be damaging the thread (unless it's utterly kaput):


Also did the spring nuts, again, if you can spin it down with your fingers, then the thread is correct and you're not cutting it anew.


Then I went looking for a 1/2" bolt or stud for the new pressure plate.... because it's a got smaller hole for the adjuster grub-screw!!


Annoyingly I could find anything at all (well, there's a couple of old bits of knackered stud... but: ) and also not sure what the thread is: so - will likely just order something that is guaranteed to fit from the same supplier.

hey ho....
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British Bikes / After the rides done, wheres the best place to find someone whos just as keen on classic bikesand ma
« Last post by expatriot on September 01, 2026, 12:47:42 AM »
Ive been riding all weekend but my garages getting lonelyanyone know a good spot to meet fellow enthusiasts who arent just into the bikes?
 
 
 
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