End float spacer for main gearbox shaft C15

[DAVE BRADY]

Hi,

I have just done this and because of the excessive end float that was there the splines were slightly worn so I needed quite a lot more and ended up with two shims.
As there is nothing holding the shaft to one side or the other they also seem to as thrust washers. Also the clutch is on the one end and it will move in and out by the amount of end float available so barely feelable is what I went for.
I would think that washer/spacers that can be filed may be a bit soft. I found some proper gearbox shims in my box of bits and spent many hours reducing it on emery paper laid on the base of a pillar drill to keep it as flat a possible. I did not use a gasket.

Dave.

To avoid removing my fingerprints and to keep the spacer flat I used a round flat magnet from an old tank bag. This reduced the need for too much pressure from fingers.  Some WD40 also helps to get it moving.

Dave.

[Derek996]

I would try to get a method of grinding the Spacing Shim to the correct thickness.  One method which springs to mind, would be to put a round peg into a Vice and use it to hold the Spacer.  Then lightly touch an angle grinder onto the Spacer and it should rotate around the peg, on top of the flat jaws of the Vice. The angle which the grinder touches the spacer will determine how fast it spins... Be prepared to have to find it if it flies off across the garage..!

When grinding Ducati valve shims I lay a sheet of wet & dry onto a sheet of plate glass (I saved it many years go from the front of a 1950's TV). Then, with a squirt of oil on the wet & dry, rub the face of the shim on the wet & dry using a figure eight motion, this helps grind the shim evenly. A 120 grade wet and dry works fine. I check the thickness of the shim after about every minute of grinding, it can take a while if you need to take of more than a couple of thou. I'm sure this method could used to grind your gear box shim safely without it flying off into space.

[Stubaker58]

My plate glass is an old fridge shelf!
Same technique otherwise.

[Barnsey]

Okay,  right now the innermost gear (sleeve gear?)  is still in place being attached to the sprocket, so I will once more gird my loins and remove this in order to check that it is correctly fitted. 

  (I am ending up with a pile of parts... I do hope that they will all go back together!)

   Assuming I don't find anything wrong I will try fitting the 0.070" shim washer which I ordered to replace the 0.074" washer, and see if this makes the difference.

   If it doesn't give the required play I will take a look around for a piece of plate glass and start grinding. 

  The idea of attaching the washer to a magnet is a good one.  I have a hefty rare earth magnet, but it is super important to use this with a glass plate, not a steel datum table for obvious reasons (Whack!  Ouch!) 

  Expect an update next weekend. 

   BR, 

   Ian

[Barnsey]

As an update,   I trial fitted the 0.070" spacer, but the shaft was still locked up.  Hence I have ordered a deep socket to remove the 1.5" nut which holds the sprocket and the sleeve gear in.  If I had thought ahead I could have ordered this a week ago!  DOH! 
 Under the nut is a big washer with the edge folded up to lock the nut.  Does anyone know if these are available?  I guess I need to replace it with new.   

[scifi]

Hi Guys, let's just see what the purpose of the thrust washer really is...

When the gearbox is in gear, as the gears are straight cut, there should be no axial thrust on the washer.  The only time it takes up slack is when the clutch lever is pulled and the clutch plates are under tension. This tends to pull the mainshaft out towards the clutch assembly.  The amount of clearance, say 10 thou, is subtracted from the amount of movement of the clutch friction plates.

If the clearance is more than this, you could run into gear selection problems, as each gear only moves about 3/8 inch, from one gear ratio to another.

Am I right in saying the far end of the mainshaft is located in a phosphour bronze bush..?  Maybe this needs   some adjustment, as well.

[Barnsey]

Yes there is a bronze bush. As per previous discussions the depth of the flange on the bronze bush looks to be correct.  I could rub off a few thou, but it might be tricky what with the bush being pressed into the side cover. 

[DAVE BRADY]

Hi,

From recently doing the same job the best way is to get the shim right.
Taking the sleeve gear out will not make any difference.
It does not take much fore then shaft to be tight. Without the gasket try turning the shaft. Does it turn at all? If it can be turned then a few thou could make all the difference. Just perceptible clearance is what I aimed for.
Consider that as the clutch moves outwards the4 primary goes out of line by the same amount.

Dave.

[Barnsey]

The clutch isn't fitted right now.  Just to reiterate, it had a 74 thou spacer fitted, which should have been more like 90 thou.  With the new side cover fitted, and the hex bolts tightened, the main shaft was locked solid. Fitting the gasket gave enough clearance to free it up.  I think the gasket was about 13 thou.  Fitting a 71 thou spacer, without the gasket resulted in the shaft being locked up again. 

 SO, I could just fit the gasket, or I could file down the shim and the bronze bearing, but, whichever way you look at it something is plain wrong. 

  The side cover is a replacement for the two previous ones which were cracked, probably due to the main shaft being bound. 

[Barnsey]

It's been a couple of weeks, as I have been away on holiday, but I am back to looking at the bike.

Removing the sleeve gear revealed nothing obvious.  I am wondering if the ball race may be non-standard and slightly wider than the original. Hence I am reassembling. 

 Question:  What is the best way to do up the sprocket nut to the required 100 ft lbs?  I'd swear it wasn't done up any where near that tight before, as it came off easily.  When I start to tighten it up I just spin the back wheel, even with chocks.  I was just using a pile of planks, so I might have to make up a proper chock with wood screws. 

  I could screw the chock to the floor of my cabin, but I will save  that as a last ditch option.  I don't really want screw holes in the floor. 

  BR,  Ian

[Barnsey]

 I managed it!  I chocked up the wheel and stood on the brake pedal (conveniently on the left on a brit bike!)  , and did up the nut with my torque wrench. I just about managed the whole operation single handed without having to shout for help! 

[Barnsey]

The saga continues:

    I refitted the clutch and checked the alignment against the crank sprocket.  They were both nicely aligned until I refitted the engine cover on the nearside and it pushed the clutch sprocket out of alignment by maybe 2mm.   

  I have ordered a new shim kit and oil seal for the primary sprocket, but I am wondering if the main gearbox shaft is just too long.  Is that possible? 

    BR,  Ian

[DAVE BRADY]

Hi,

2mm is a huge amount.  When you say nearside engine cover, do you mean the primary cover or the timing side? The primary cover does not touch the clutch and if it did it would push it inwards.
With the timing side inner fitted there should only be the end float that you have already achieved by fitting a 0.071 spacer and the gasket with a resulting end float of - .  Fitting the clutch should not make any difference with the end float remaining the same.
I see from your first posts re 'wiring loom' that the bike was running so it is very unlikely that the shaft is too long.

Dave.

[Barnsey]

Actually there are some marks where the engine sprocket and chain have been catching on the casing,  so I think that maybe a previous owner made a mistake in setting up the alignment.  Maybe they shimmed it with the timing side cover removed. 

[DAVE BRADY]

Hi,

Can you post some pictures of the primary side to show the marks. The engine sprocket should not be able to touch casing whereas a very loose chain could.  Is there a primary chain tensioner fitted?

Forgive me for asking a stupid question but just trying to visualise what you are describing.  Did you fit the spacer on the end of the shaft that goes through to the clutch rather than at the other end?

Dave.