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[stinkwheel]

This is a copy of a build blog post I made on another forum. The language is probably a tad "younger" than many are used to on here. I'm not saying everything I did is correct but people might find the pictures handy if nothing else.

Ok. Stripping an albion 4-speed gearbox. These gearboxes are a 1940's design and weren't regarded as particularly pleasant to use even then. What they lack in finesse, they don't really make up for in functionality. I'd say they are the second worst gearbox I have ever used, the worst being the one fitted to an Estonian home market Ural.

One thing you can do however is piss about with them. i'm going in to change out two of the gears which will radically alter the gearing for trials use.

Standard ratios: 1st = 2.78:1, 2nd = 1.84:1, 3rd = 1.36:1, 4th = 1:1.

New ratios: 1st = 3.19:1, 2nd = 1.97:1, 3rd = 1.46:1, 4th = 1:1.

You'll notice 4th remains the same because it's straight through. So I'll land up with three super low gears then an enormous gap to 4th which will be road speed, because it's geared down 2 teeth on the front, it should pull 4th in most road conditions and sit at 50-ish. if it won't, I'll be stuck doing 30mph until the hill flattens out.

The other thing I want to do is fit a bronze bush on the layshaft because the cast iron one is picking up when I give it some wells and swinging the kickstart down (I'll explain this when i get to it).

Lots of detail because someone requested it.

First remove the kickstart, gear lever and neutral finder lever. It helps to put it in gear first for reasons which will become clear later.



Undo the slotted screws, remembering that the top "keyhole cover" screw also holds the gearbox cover on.


Unhook the clutch cable and lift the cover off.




Undo the two half nuts holding the stop-plate on and remove it. This will expose the ratchet assembly.


The whole ratchet assembly lifts off. As does the foot control lever.




The gear operator selector assembly locknut (hex nut at the top right) needs to be removed.


The bottom bolt on the ball bearing cap also retains the kickstart return spring, once undone the spring can be removed. Try to support this bolt in position when undoing using a socket. As it nears being undone, the spring can rock the last coule of threads out, damaging the alloy.


The two pins holding the adjuster plate on have two flats on which can be undone and the plate lifted off with its springs in-situ.


The final bearing cap nut can be removed and the bearing cap tapped loose. You can also pull the clutch pushrod out which runs through the centre of the hollow mainshaft. There may be a ball bearing stuck to the end, don't lose it!

This exposes the mainshaft nut which has a tabbed washer. THIS NUT IS A REVERSE THREAD. This is why you put the bike in gear before. You can hold the back wheel with one hand and undo this nut with the other. If it's in neutral, the shaft will just spin. If you need to put the bike in gear now, you can rotate the square shaft with a spanner as you are turning the engine and you should get a gear.


The bearing is not sealed. This is why these gearboxes are grease and not oil filled. Now undo the 5 slot head screws (there are two under all that nasty yak at the bottom).

Do not remove the hex-bolt at the 10 o' clock position to the kickstart shaft like I did here. It holds a crescent-shaped detent for the kickstart pawl in place and it is a real fiddle to get in the proper position.


The whole outer cover should now lift off, taking the kickstart shaft with it. This is the inside view.


And the inside of the gearbox is now in sight.


One more thing that can be done from this side is to remove the gear operator pin bush. It's on the back of the gearbox, facing the rear wheel. It's a total sod to remove because while it's slotted, it has the end of the shaft protruding out of the middle. Idealy you'd need a huge flat screwdriver with a notch in the middle. I may well make a tool for this before reassembly. It's also really hard to reach.

Once the bush is undone, the pin can be removed which frees up the selector forks inside the gearbox.

On reassembly, it became apparent that it was not necessary to remove this pin! Once the mainshaft has been removed and the layshaft pulled back out of the left hand bushing, there is enough play to lift the gear operator off the forks and slide the gear clusters out. It is a fiddle but do-able.





Further dissasembly requires removal of the primary chaincase. A job for tomorrow I think because I spent most of the rest of the day getting the old layshaft bushing out.

[stinkwheel]

]This is the kickstart shaft. The layshaft runs in the end of it in a cast iron bushing.

If you make a smart getaway, instead of the layshaft rotating in the bushing, it can pick up the kickstart shaft and rotate the kickstart backwards. On this bike, it hits me in the shin. The solution is relatively straightforwards, you simply replace the cast iron bushing with a bronze one.



The less straightforward bit is the cast iron bush is fitted in a blind hole in a steel casting. It's been in there for 15 years/90k miles...

I had a cunning plan to use an M10 rowlbolt as a puller (the old bearing was just being used as a spacer, it was knackered anyway).




This did not work, it wouldn't budge, not even with heat. I'm not convinced a blind bearing puller (the correct tool for the job) would have got sufficient hold either.

So plan B. This bush IS cast iron, not steel so it is soft and brittle. It's 22mm OD so I first ran a 20mm blacksmiths drill up the middle to leave me with a much thinnner "shell" of bushing.




I was then able to break the shell in by abusing an old screwdriver.






The above took a long time!

I then tapped in the new bushing having heated up the shaft.



Only to find it would no longer fit over the layshaft, despite having checked it did before fitting. The shrinking of the steel must have also contracted the bronze. This is fairly usual and the normal thing to do is to run a reamer tool down it in a mill or lathe. I have none of those so my solution was to very slowly and gently ream it out a bit at a time using wet and dry paper taped a bit of steel bar a bit like using a fire drill until it was a good fit.



Quite a successful day so I'm leaving it there for now.

[stinkwheel]

Continued. There is a nut on both ends of the gearbox mainshaft. The other one is a bit of a bugger to get to because it's in the middle of the clutch.

So primary chaincase off with drain tub underneath (there is no drain screw, you just have to crack the cover and let it run out). You'll need to remove the footpeg on a normal bullet to do this.




Here's where I cocked up a bit. I didn't really need to remove the alternator as it happens, I had it in my head the whole primary chaincase would need to come off, and this would have been the case if I needed to fully strip the gearbox because the nut holding the final drive sprocket to the mainshaft sleeve is behind the chaincase.

However to change out the gearing here, I just needed the remove the clutch plates and centre nut. Too late was the cry, alternator came off too. three nuts and the stator lifts off.



Remove the primary chain tensioner because the next step would put a fair bit of force on it.


Then lock the primary chain with a piece of folded denim and undo the crank centre nut (normal direction thread).


Altermnator rotor slips off and put the Woodroffe key somewhere safe.


Undo the three screws on the clutch pressure plate and the pressure plate and clutch plate stack can be lifted out, exposing the centre nut.



Centre nut is easily undone with an impact wrench, or with a great degree of buggering about with special tools without an impact wrench.

Remember to remove the "top hat" from the end of the clutch pushrod. Also remember there is still a section of pushrod and possibly a ball bearing inside the hollow mainshaft.


Once the clutch centre nut is off, the mainshaft can be pulled out fromt he gearbox end.

NB. There is an oil seal in the inner chaincase behind the clutch. Dragging the clutch splines through it could well damage the seal. It would be a good idea to wrap the splines in a bit of plastic bag for this bit, or be prepared to replace the seal (this can be done once the clutch basket is removed).



Don't forget to remove the gear operator selector.


Once the mainshaft is out, it creates slack inside the gearbox. We already removed the gear operator pivot pin. The gear operator itself can now be lifted up off the two pins on the gear operator fork. Then the whole gear assembly can be lifted out of the gearbox (leaving the mainshaft sleeve and low gear attached to the bike in the back of the gearbox).



You can see the ends of the gear operator that you lift up and disengage from the selector fork more easily when the gears are out. This picture also shows the mainshaft sleeve and low gear still in-situ and below it, the bushing that receives the far end of the layshaft (which is already bronze on this gearbox).


I now have the bits I want. I'm replacing two 15 tooth gears with two 14 tooth gears. That's it. One is pressed onto the left end of the layshaft, inboard of a bushing which is also pressed onto the splines. This took a lot of force on my puller AND quite a bit of heat to remove.





Two new gears:


The other is on the end of the mainshaft, there is an oil flinger outboard of it and a dog inboard of it. The dog can stay where it is.



Two leg puller wasn't man enough. The three leg needed winding until it creaked, again a lot of heat. Goggles on, this much force on case-hardened gearing is a recipe for sharapnel if something lets go!



Fitting the new ones was pretty straightforwards. Shaft int he freezer, gear in the oven and that got them halfway down, i then used the old sprocket as a drift to tap it on the rest of the way... One day I'll have a fly press

Only one casualty so far which was the gear operator selector which is a sprung detent. I over tightened it and mullered the end. New one on the same order as the grease, they are only £6 and so it's not worth fixing.



Just needs putting back together now. Breaking that detent was mu cue to stop for the day.

A note to anyone doing this. I have heard of cases where the old sprockets will simply not come off the main/layshafts. I suspect there was insufficient determination/persistance with the puller and a reluctance to roast the hell out of it until the grease is smoking out of the joint. I alternately wound the puller up, applied heat, tapped the end, gained another 1/8 turn on the puller, applied more heat, tapped the end and so-on. I was waiting to be hit in the face by a red hot gear but it actually came off in a fairly civilised manner in the end.

I hate re-fitting alternator stators on these bikes, they need shimming and it's a pain in the balls. I wish I'd thought about it a bit more, it could have been left in place.

[stinkwheel]

"Re-assembly is the reverse of the above."

One of the most oft-repeated lies in workshop manuals.

It's also become apparent there were a couple of steps i did before that were unecessary and slowed the job down. I'll go back and edit these.

Here's the new gear operator selector. It seems to stick out further than the old one ever did which makes me wonder if the old one was defective from the get-go.



So first step is to get the gears back in. You need to insert the layshaft along with the selector forks and two central gears from the mainshaft as a group.


Once the mainshaft gears are located on the splines of the outer shaft, you can let the layshaft drop down slightly and engage the selector forks with the notches of the gear operator. Then the layshaft can be advanced all the way in and engaged with the bushing at the back (left side) of the gearbox. At this point, the mainshaft can be re-inserted.

It is worth noting that it is perfectly possible to insert the gears with the mainshaft cluster on backwards so make sure the small one is to the outside (right side)... Don't ask! Also check both gears are still captive in the selector fork after you engage the gear operator.



This bike will be ridden through floods and there is nothing preventing water getting into the outer compartment of the gear casing. You can see the corrosion that has occurred from trapped water on previous pictures. it also caused some corrosion and friction between the kickstart shaft of the gear selector shaft which has the odd side effect of occasionally engaging first gear when you kick the kickstart. I can't stop water getting in, but I can make sure it can get back out with a high-tech modification!




A visual inspection of the kickstarter pawl shows it to be in pretty good order. if it's worn, now is a good time to replace it. Here's the whole mechanism reassembled.








Here's one of the places I made a mistake. See the bolt at the 10 o' clock position to the kickstart shaft in the picture below? Don't remove that. It holds a little crescent-shaped steel detent that acts as both a stop for the kickstart and disengages the pawl from the layshaft. It's a bit of a fanny to get in exactly the right position so it retracts the pawl properly but doesn't foul the shaft itself. I spent a long time fiddling to get it put back!



The gear operator shaft is on the inside of the outer gear case. When reassembling it needs to be rotated so it engages with the end of the gear operator. You can also see the crescent-shaped kickstart detent near the bottom of this picture.


The selector engages on the end of the piece of flat steel in the centre of this picture.


It seems best to have the kickstart shaft inserted into the gearbox cover with it rotated into the fully "up" position (so the pawl is retracted) for reassembly.

The selector shaft needs to be rotated into position as you advance the cover, engaging the kickstart shaft with the end of the layshaft and gently moving the end of the mainshaft into position in its bearing with a finger of your third hand. At the same time try not to dislodge the new gasket.



The gear operator selector should be screwed in ensuring the slot is paralell to the ground (and therefore the pawl is aligned in its slots). It doesn't go all the way in. If you put a spanner on the end of the gear selector shaft, you should be able to feel how much resistance you are causing, you want enough to hold it in position but not so much as it's stiff.





Install thye mainshaft oil flinger, tab-washer and nut. Remember the nut has a reverse thread!


Mainshaft cover on witrh the top bolt.



Engage the kickstart spring with the hole in the kickstart shaft at the 9 o' clock position. Then rotate it clockwise and hold it in position with trhe bottom mainshaft cover bolt.


Loosely attach the adjuster plate assembly using the studs. This has slotted holes which will need the position adjusting.



Slide the foot control lever on ensuring it engages with the sprung tabs on the adjuster plate.



Similarly engage the ratchet assembly into the sprung tab at the top and foot control lever at the bottom and loosely screw the stop-plate to the outside with its two half nuts to hold it in place.



Now adjust the position of the adjuster plate so the "resting" position is roughly in the middle of the stop plate stops. If it is too far one way or the other, it will hit the stop plate before the selector ratchet engages and rotates the shaft. Lock it down by tightening the studs, then tighten the half nuts. This can take a few attempts to get right. The ratchet is also prone to wear and may need replacing if it's not engaging properly.



Slide the clutch pushrod (and ball bearing) back in, re-engage the clutch cable, screw the outer cover on and you're done. Check it gets all the gears and that the kickstart works (you'll need to reassemble the primary drive to do this).

I'll admit, I had to take the whole lot apart again becauase I wasn't getting any gears and I'd put the mainshaft gears in the wrong way round! Surprisingly quick to strip and re-assemble second time round though.