clutch AND gearbox now !

Sounds like the earlier clutch  which  I am not familiar with. The inner case may be not secured in the right position or the  hub spider internal stop may not be doing its job  allowing the clutch drum to sit too close to the innercase.

There’s a bearing at either end of the mainshaft, but unusual for it to be tight unless something is out of line like a bent shaft. I don’t understand how the chain can hit the back of the clutch because the chain case should be between them! (I assume this was with the chaincase removed!  But if it is that close, like Robert, I’d suspect that the clutch spider is worn and the clutch is sliding too far down the mainshaft. There should be a stop that lets it sit against the end of the shaft. It is possible that the clutch body is also touching the end of the sleeve gear which will tighten everything up - was the clutch loose when you tried it without the plates?

The number of plates shouldn’t be causing the mainshaft to be stiff? But yes there are two types of clutches one has the friction material on the basket and one doesn’t. I can never remember which is which! One has the bonded plates with the tangs outwards and the other has the tangs inwards. They cannot be mixed for obvious reasons! 

Dan 

Some thoughts. If your spider has started to  'climb' onto the gearbox mainshaft, I cant see it being easy to 'shim' it as it is a splined fit and inside the spider and there isn't much (any?) room there. Could be time to remortgage and get a new centre!

Don't forget that on some(maybe all? an expert will surely know and give his/her wisdom on this) of the clutch types, one of the friction plates is a 'one sided' plate, ie. there is friction material on one side and plain on the other. This goes next to the pressure plate. This may be only on the clutches with a plain basket though. Familiar with those as that is what my bike has.

Also check the gearbox sprocket tightness isn't due to the oil seal binding on the sprocket or the spacer being too tight within the seal. 

Good Luck,

George.

RGM sell a new spider that has a proper (full circle ) register that solves the problem  of migration up the shaft.   Its the only answer . Your orriginal is scrap . Once this problem starts the clutch will sometimes jam up on the shaft and need a decent puller to get it off. Fitting the spider is fun, need a ground flush socket to get a grip on the very shallow nuts  to seperate the race plate. (which is shown back to front in some manuals !  Then I would recommend  checking the roller/race clearance  with a feeler and if more than  3 thou get a set of 1 thou oversize rollers which will  reduce clutch wobble and transform your clutch /gearchange. Have fun fitting your new clutch rubbers too.  Forget asking any Norton suppliers  for the rollers , and no,  a new race plate will only be worse than the old. They dont make things like they used to !!.

Hi Terry,

I can only symphathise with your 'can of worms'!

Preload on mainshaft - has 'instant gasket' been used between inner cover and gearbox case instead of the proper gasket? That would take up a lot of the clearance.

Regarding the sliding seal holders, it sounds like they have been incorrectly fitted. The two halves should be installed facing away from each other such that there is a gap of around 3/16" (from memory - could be bigger) between them at the shaft hole. It is into this recess that the felt goes. It can only be put in with the case off. Even with the felt in place, excess oil can stop your left silencer rusting if the crank seal goes/ doesn't do its job, so I can only imagine it would be bad without a felt.

From the RGM website here is a picture of a Commando case with the discs fitted correctly. 

Regards,

George

Personally if the clutch is migrating up the main shaft, I’d buy an RGM or Andover spider, Fun to fit but not impossible! Machining the boss won’t stop the back of the clutch rubbing on the chain case it they will in due course. The primary chain will also move out of line. 

Ive just fitted the sliding seals to my chain case and confirm that the seal fits between them. 

I have both a Norton and AMC clutch in the garage, I’ll try and have a look at which is which. Although I’m sure the manual or parts book will explain! 

Your bigger problem is in the gearbox, the clutch is relatively easy to solve. Have you got one of the gearbox DVDs? 

As far as the clutch plates go the earlier (Pre 57) Norton clutch had cork inserts in the basket while the later AMC clutch had the friction material in the basket.

When counting the plates: Do you have the double sided plate on the end? Next to the pressure plate?

And remember, later clutch baskets were longer to hold the extra plate in.

As for the sprocket being hard to turn: sounds like a bearing job.

Some owners tighten the clutch nut  very hard  to stop it coming loose . The orriginal spiders have   a very small   segmented register  that is weak.  This buckles and partly rides up on the box shaft allowing the clutch to move into contact with the sleeve gear end. Grinding 20/30 thou off the back of the clutch  seems a solution ,but is not. as it just accelerates the issue .  Tried this ! . It just made the clutch impossible to get off without brute force .After repair I limit the nut torque to about 35 ft lbs   and use a very close fitting washer under the nut to provide support and a little drop of nutlock. The axial load that this issue puts on the box bearing is probably  very bad for it. The RGM spider I bought is about a third of the cost of the Andover part and was  ok with a full circle register (that cannot be seen on the photos). 

I found the Mick Hemmings video a great help, the gearboxes are very straightforward. It’s possible that your mainshaft hasn’t seated properly, but they have been known to bend! 

Regarding the clutch I’ve copied this from an other thread - I searched on “Clutch Types”if you click on this blue text it should take you there. So Mikael - let me start…

So Mikael - let me start with the AMC versions of clutches that came in with the 1957 Models. All of them share common parts but some parts are peculiar to specific models.  So the Model 50 has seven plates, the ES2 , 88 and 99 have nine plates whilst the 650, 88SS, 99SS, Atlas and Mercury  have eleven plates.  Because they all share the same drum and centre they have different thicknesses of pressure plates to suit with the heftiest on the Model 50 and the thinest on the 650 etc.  The 650 and SS models also share thinner bonded plates, a stronger shock absorber centre, longer spring studs and stronger springs.  The Model 50, ES2, 88 and 99 use the same parts except for there being two plates less and a different pressure plate on the Model 50.  All these clutches have plain steel plates with location tags on the outer rims and bonded plates with tags at the inner rim.  They all appear to have been attacked by a nail gun during the manufacturing process.  The sprocket/drums for all these clutches have a ground surface both sides.  The mainshafts in all these models gearboxes are the same length so clutch adjustment is determined from the pressure plate, spring tension and adjustment screw whilst the clutch position is fixed by the mainshaft and clutch centre machining.  The AMC Manx clutch does not share many items with the road bikes so I mention it only for completeness.

Prior to 1957 all the post-war models used the Norton Burman gearbox and clutch.  These clutches have friction plates with tags at the outer rim and steel plates with tags on the inner. The clutch back-plate is plain so the sprocket/drum also has friction material. Many of the dimensions of these components are the same or very close to the AMC types so there are many opportunities to use odd combinations of parts.  There are many different mainshafts and clutch centres for the various models to fix the  position of the clutch. Some of the early plates used separate pieces of friction material and in the drum whilst many had bonded on material. Also many workshops modified the parts to fit or improve accordingly.  The pressure plates had a fixed centre but many people fitted an adjustment screw. 

So you can see why there are many pitfalls possible with Norton clutches, Pre-Commando of course.  It's a nightmare if you don't buy an assembled item.  Caveat emptor !!  cheers, Howard

Dan    

If the clutch drum is sporting a large circlip then it is either off a Commando or very, very early Dominator.

.. has a circlip (although I have discarded it). It appears in the parts list as part number A2/398 described as "clutch plate retaining ring".

.. before anyone is misled it's the clutch centre that has the circlip (or plate retaining ring) on my 1952 model.

I used small pop rivets to join my Sealing plates, there is room, but you also need to make sure the slot in the chain case is the right size for it to slide in. 

Sounds exciting,  why don't i have this much fun?,  have to find a basket case.

Hi

I've followed this interesting thread for a while as I encountered similar problems (some years ago) fitting a belt drive conversion to a 1956 Dominator with an AMC gearbox. The Commando clutch was catching on the back of the chain case. I took the clutch and an old shaft to my local sheet metal works. They had a CNC machine and using measurements from the shaft and the back of the clutch they were able to make me some spilned shims to fit to the shaft therby 'pushing' the clutch outboard in the chaincase. It cost me £20.

This was mainly spent on setting up the machine to do the cutting from a piece of scrap 1mm sheet. The piece of scrap was large enough to make 6 such shims so I had 6 made. Two I used myself to aid fitting belt drives to my two Nortons. The rest I gave away to friends encountering similar problems.

Hi Terry,     You are not alone in having bought a "PUP"   My last 3 bikes were the same  Beatifull looking lash ups ! .  Much better to buy a cheaper scruffy well used bike.   With respect to any shims , Things will still work with the box sleeve gear under an axial load from the clutch ,but it will not work as well as it should.

Good . It takes a very close look into the spider  to spot the problem.  In fact every part of the clutch needs close scrutiny  if you are not to be doing the job  again later. Guess how I know this !! . After years of tinkering  I can now sit at traffic lights with the clutch held in. Select neutral at a standstill and get first gear without a crunch. I can also pull the clutch in with one finger .  Its only been 25 wasted years  struggling  to get there.

For a time RGM were selling slightly wonky spiders at a very discounted price, I think they still worked ok. I have looked around for some OS rollers ,can't remember where I got them but they are not easy to find. I have a spare set .but am intending to fit to the Atlas clutch which I also intend to modify to incorporate the Kegler  servo/slipper  action  as son who rides it  has a weak grip. Just can't resist tinkering.

You need enough clearance to get the rollers in ,so 1 thou remaining  is good.  I had 31/2--4 thou so  loosing 2 thou was great.  This is a mod from the old Norton race bikes where if you had a draggy clutch your chances of a fast bump start and first off the line were gone.With less wobble you will also find that the outer edge of your plates no longer leave marks in the drum ! .

If the layshaft is a bit tight and is causing the box to be stiff, Mick Hemmings recommends tapping the end of the kickstart shaft to get it to seat correctly.

dan 

Brilliant, I love a simple fix, but the credit is due to Mick! 

Now all you have to do is get the chain case and clutch sorted!  If you fit a new spider it helps to use an old mainshaft to hold it and make a clutch holding tool out of an old clutch plate so you can fit the rubbers (get new ones) I made sure everything was clean and used some silicone gel to help get them in. It was still a bit of a fight! 

Dan