Charlie's Shed - Cables & Cable Making

Updated - first published February 2014

This is the section where we deal with those cables that you oil regularly, that operate your clutch and your front brake. They are an important part of your biking experience, not only for your safety but also to make the experience a pleasant one – there something rather magical about you & your bike cruising smoothly along a sunny lane, with everything operating as it should. One of your main connections to your bike is through those control cables:

Cables & Uses

Since the dawn of the bicycling era we have had the Bowden flexible cable. Your typical old motorcycle will have several – for the front brake, the clutch, the throttle – and maybe for the back brake, an air slide, a decompressor and the magneto as well.

You may have noticed that these cables are not identical – in fact there is a whole variety of components used in control cables throughout the biking world. Like many other facets of life, cables have their own jargon. Here are the keywords:

You might recognise this as something like a Bantam clutch cable – though Bantams have the adjuster mid-way along the length of cable, not at one end.

Cables are manufactured from multiple strands of high-tensile steel wire, formed into a cable (i.e. twisted together in contra-rotating layers) provided with a compression resistant outer casing formed as a spiral of rectangular section wire, covered in a PVC or cloth sheath. The outer is finished with a pair of ferrules at each end, to protect the ends, and the inner is fitted with a pair of nipples, usually brass, to allow the handlebar lever or twist grip to pass the load into the cable, and the cable to transmit that force into the clutch, brake, or throttle slide.

Talking about loads, of course we realise that the load passed into a throttle slide is far less than the load that is required to bring a heavy bike to a stop with the front brake. So, we need several different cable sizes to cope with these loads – we don’t want to operate the tiny throttle of a BSA Bantam with a cable suitable for the rear brake of heavy bike like a BSA A10, because it would be way too stiff and the friction alone would probably stop the throttle closing.

So there are several cable sizes in use:

It’s useful to note, when you are buying cable components that several of those inner wire diameters are similar – 0.062” is not so very different from 0.075”, so be careful when measuring!

When you have bought your inner wire, store it carefully. One of the key elements of successful soldering is cleanliness - solder will not 'take' to greasy wire or to wire that has been out in the weather for a while. The inner cable should be free of grease and the plated wires should be shiny - dull corroded wires may not solder at all.

Outer Casings, Nipples, ferrules, inners etc.

So, to help you decide which components you need, here are some tables identifying the various parts:

Inner Cables & Ferrules

Here are the dimensions for the corresponding casings & ferrules for those cables listed above:

Nipples  

Occasionally you'll find a nipple application that you can't buy, in which case those of you with a lathe and some brass bar can make them yourselves. Here's how I do it, in the post 'Free the Nipple'.

Sometimes, nipples are fitted with plastic sleeves to reduce friction. These can get mangled but you can make a sleeve (here's how I do it) to replace them:

Buying Parts

There are a few suppliers offering cable making parts shown on another page. Shop around though, since nipple prices seem particularly variable. It is probably wise to buy your inner cable and outer casing from the same vendor.

Making up a cable

You’ll need to determine some details of the installation before you start on making up your cable. First of all, check out the cable size using the tables. Determine the length, during ‘Routing & Laying Out’. Look at the sizes of the appropriate ferrules – you must make sure that the ferrules fit inside the adjusters on the handlebar levers, brake plates or wherever or inside the levers themselves.

Then, take a look at your nipples – use the tables to determine what you might need, and then look at the handlebar levers, the brake arms or the clutch arm – whatever parts you are trying to control, to determine what nipples you need.

Note that some nipples will only fit certain sizes of inner cable, and that the handlebar levers you have may be damaged – bent levers result in poorly fitting nipples or ferrules.

Routing & Laying Out

Now it is research time. Try and get a look at some other machines, or pictures, to get an idea of how the cable was originally laid. Think about whether the cable routed behind the headlamp, in front of the yokes, down behind the fork leg or in front of the fork leg, which side of the fuel tank it went; under the engine, over the engine etc.

Keep it away from hot parts like the exhaust or cylinder head; make sure that there is enough length for the bends to be long and sweeping – with a large ‘bend radius’, and check that out with the steering in the straight ahead, full lock left and full lock right positions. Sweeping bends and good routing are the secret to smooth acting, long lasting cables.

Try and determine how the cable was tied to the frame and whether any guides or clips were originally used. Once you have this figured out, run a length of your chosen outer casing along the route and have a think about it. When you are happy, you can cut the outer casing.

Cut the Outer Casing

The outer casing is made from a rectangular section steel wire, hardened to provide a strong, flexible and incompressible outer casing. It’s covered with PVC to provide weather protection, retain lubricant and to make it look pretty (these are available in a variety of colours for all you Ariel Arrow sports riders).

All this makes them a little tricky to cut. Good side cutters or a sharp chisel are usable, but cannot provide a square end; not strictly necessary, but if you want it, and a square end allows the ferrule to fit over more of the casing and to be retained more reliably, you can use a cutting disc in a Dremel or similar tool. This results in a neat square end, and the PVC, which will have melted somewhat can be cleaned up with a sharp knife.

Ferrules

The ferrules are often nickel plated brass or steel. They vary somewhat from supplier to supplier and may be brass and hard; or steel and soft. They should be a sliding fit over the end of the outer casing but if slightly tight their fitting can be aided with a little detergent or something more readily available (I usually use a bit of saliva! Good lubricant for rubber, saliva) they should not push the PVC out of shape when they are fitted.

If they are tight, you might choose to leave them as they are; you can tap them in one place with a dot punch; you can crimp them with pliers. After I had made a few cables, and never been very satisfied with any of these methods, I made a simple swaging tool from two pieces of ½” square bar. The bar has a variety of holes, sized to suit the OD of the ferrules, less 0.5 mm. Therefore I have a series of stepped holes – the ferrule OD, and the ferrule OD less 0.5mm.

You will notice from the picture that this swaging tool, made from two bars, has the holes drilled such that they can be split. The modus operandi is to place the ferrule over the casing, and then place the ferrule in the tool such that the bottom 1/16” or so of the ferrule is gripped by the smaller of the two diameters in the hole.

The bars are then squeezed in the vice, and the ferrule is swaged such that it grips the cable outer casing. This works with all ferrule materials, but the harder brass ferrules are inclined to split when swaged. The steel ones work beautifully though.

First Nipple

Which nipple you fit first depends a bit on the installation. The trickiest part of making a cable is cutting the inner to the right length, at the second end. If you mess it up, the inner might be too short – in which case you have to start again; if you make it too long you just have to re-solder. So, I like to fit the most accessible nipple last. Usually this will be the handlebar end, but in this example I am making a front brake cable, which is very accessible both ends.

Fit the first nipple over the cable end, with the belled-out side away from the inner case ferrule. It should be a nice sliding fit on the inner cable.

The next step is to prepare the inner cable for soldering. It goes without saying that these control cables are vital for your safety and proper preparation of the cable, proper soldering (including selection of the solder) is vitally important!

There are two types of soldering technique to consider – hard soldering and soft soldering. Hard soldering involves the use of a solder containing a high proportion of silver, and temperatures up to 750°C. This involves the use of a hot gas flame and incurs the risk of annealing the cable (since most hard solders melt at a temperature higher than the tempering of the wire in the cable), leading to the possibility of the material yielding and the cable stretching - or, if you were foolish enough to quench it, the wire will harden and break potentially with catastrophic results.

Soft soldering on the other hand involves the use of solder containing various proportions of tin and lead, and temperatures of below 400°C, which will not risk annealing the steel wire. Soft solder can be heated using an electric soldering iron or a solder pot, and the temperature will be easily controlled avoiding the risk of oxidisation or weakening the wire.

Soft solder is made in a variety of ‘recipes’ for various uses:

You will note that the solders listed vary in their strength according to the constituent components. A Lead free Tin/silver alloy is the strongest and therefore the most suitable for our purpose these solders melt at 250-300°C, suitable for a conventional soldering iron.

Solder is available in bars and wires, both with flux cores and without. I use non-cored wire solder, since I like to be able to control what flux I use.

So, you will need some flux. Metals at higher temperatures are even more prone to oxidisation than usual – so we need something to prevent oxidisation during soldering, otherwise the solder joint will be weak and will fail.

The impurities can be removed by mechanical cleaning or by chemical means, but the elevated temperatures required to melt the filler metal (the solder) encourages the work piece (and the solder) to re-oxidize. This effect is accelerated as the soldering temperatures increase and can completely prevent the solder from joining to the work piece. I like to use the liquid, Zinc Chloride based ‘Baker’s Fluid no.3’ for making cables, since it flows into the joint before any heat is applied and seems to be able to keep the join clean enough to ensure a successful joint every time. It's acidic, so you don't want to drop it on anything important (like a chrome wheel rim) and you will need to clean it off afterwards.

Now, onto soldering the first nipple. Again, we use our swaging jig which has a number of holes drilled through it of such a size as to grip the inner cable, without crushing it. In the top of each of these holes is a small well of larger diameter, used to form a ball, or birds nest, on the end of the inner cable. We start with the inner cable in the swaging jig, with a length equivalent to about four diameters of the cable sticking out above the well, the jig is clamped in the vice, and the inner cable is not going anywhere.

Using a punch, we tap down on the end of the inner cable, in order to divide the strands:

Having divided the strands down into the well, we take a pair of long-nose pliers which, together with a small hammer, we use to bend the ends of the strands back toward the centre, forming a ball:

This is where the strength of the cable assembly comes from. The ball prevents the inner cable pulling through the nipple, and the separated strands provide a hugely increased surface area for the solder to grip the wire, such that the tensile load in the cable is pulling on a ball of solder and wire which cannot pull through the nipple.

So, now we can remove the swaging jig and see that the wire nest fits nicely inside the nipple. We are ready for soldering. Hold the inner cable in the vice, gently, such that the nipple is pointing downwards. We want the solder to flow into the nipple and to stay out of the inner cable; otherwise the inner cable will become stiff and your lever action will be affected.

Lead rich solders are more reluctant to flow than tin rich solders. You may find it more effective to leave the ‘cup’ in the nipple upward using lead rich solder.

Dip the end of the cable and the nipple in the flux, and apply your soldering iron. It will take a while to heat the nipple up, but occasionally touch the wire with solder to see if it is hot enough. Remember that the work has to melt the solder – the soldering iron is used to heat the work, not the solder. If the solder will melt when it comes into contact with the nipple, then the nipple is hot enough. Proceed right away, since overheating will produce more oxidisation and will ruin the joint. Allow the solder to wick down the cable, filling up the birds nest in the nipple. Let it flow until it is about to drop out of the nipple, and you’re done. Leave it to cool - do not quench it and do not move the end, or you will lose the pool of solder within the nipple.

You'll find it much easier to solder the nipples if you have a solder pot, like this one:

The solder temperature is thermostatically controlled, so there is no danger of overheating the wire and the solder will flood the joint easily. Overheating will ruin the heat treatment of the wire - in the picture, I'm showing a clutch cable that has been rendered brittle by overheating the nipple. The cable fractured just behind the nipple, leading to a ride home changing gear very carefully and hoping for light traffic - the same breakage in a brake cable could have been very different. 

Once cool, clean all the flux off with water. Flux is highly corrosive and you don’t want damage arising from yet more oxidisation. File any excess solder away, and don’t worry if you file off the ends of some strands that are poking out.

Second Nipple

Once we have soldered the first end, we can fit the cable back on the bike. Make sure that all the adjusters are in their shortest position, and wind them out two turns. We are going to make the cable as short as possible but in the event that we are a little over-enthusiastic and we make it too short, we want to be able to loosen the adjusters more if it proves necessary.

Make sure you fit the cable in its proper routing and that the second nipple is properly located in the brake lever, carburettor slide or whatever. Now, you will need to have the parts in their operating position to get the inner cable length right – throttle twist grip rolled shut, throttle slide down; brake handlebar lever fully ‘off’, brake plate arm moved such that the brakes are almost on, but not biting. You want the brake, clutch or throttle in a position where a small amount of cable movement will have it operating with the adjusters wound ‘in’ otherwise the cable will be over length.

Mark the inner cable with a small piece of masking tape in the location you want it cut – but don’t cut it yet. It’s helpful when cutting cables if they are ‘tinned’, that is, if the strands are bound together with ½” or so of solder. Fit the second nipple and keep it out of the way with a piece of masking tape. Dip the end in flux, apply your soldering iron and when it is hot enough, touch the cable with solder and allow the solder to wick up the strands. Now it won’t unravel when you try and cut it. Use a sharp pair of side cutters or the Dremel cut-off wheel for this job.

Next, you can put the second end in the swaging jig and prepare the birds nest. Solder up the second end as before

Try it back on the bike, and use the adjusters to take up any spare length. If you have to unwind them considerably to get the brake, clutch, throttle or whatever workings correctly, consider releasing the second nipple and making the inner cable a little shorter.

Lubrication

Decent lubrication is vitally important to the operation and life of a cable, and to the pleasure of riding the bike. I use one of these clamp on cable oilers with WD40:

Cable Management

Several methods of cable (and we are talking both control cables and electrical cables here) management were used in the 1950’s & ‘60’s, some more obvious than others, some more effective than others.

We are all familiar with the modern nylon cable tie, but whilst this is available in a wide variety of shapes, sizes & colours it is not in keeping with a 1950’s machine. That said, I have several on my Bantam and very effective they are.

You will find pictures of these black rubber ties in the BSA parts book for the Bantam. Originally made from Butyl rubber, they perish very quickly and fall off; modern versions are made from silicone rubber and will survive oil, petrol and sunshine very effectively

They can be used in a variety of ways giving the opportunity to strap cables of various diameters to handlebars, frame tubes or mudguard stays, and are used by passing the ‘T’ end through the hole in the opposite end, trapping the cable against the frame or passing the T through the middle hole, around the cable, and then again around the frame and into the end hole, holding the cable away from the frame. This looks rather neat I think.

Ariel made use of some rather neat steel sprung cable clips. Here are two three-cable originals on my W/NG, retaining the rear brake switch wiring - there are further ones under the tank retaining the clutch, throttle & air cables. These clips are available in stainless steel for one, two or three cables:

Spend a night in the box...

Paul Newman

Updated: First published May 2013

No man shall have worn mainshaft bearings. Any man found with worn mainshaft bearings spends a night in the box!

No man shall be missing his kickstart stop. Any man found missing his kickstart stop spends a night in the box!

No man shall forget his lubricant. Any man found forgetting his lubricant spends a night in the box!

One of my favourite films, Cool Hand Luke.

Talking of spending a night in the box, the engine is going to be ready next week and I need to have the gearbox out & cleaned because if I know myself at all I'm not going to want to tear Amelia apart anytime soon, when the bottom end is back in.

So, I've been looking at Mr. Waller's book and I need to record what I'm doing with the gearbox. There doesn't appear to be a manual for the BA, so perhaps we can write one.

Many machines used Burman gearboxes, going back to pre-war years including Ariel, AJS & Matchless, Panther & Vincent. Many of these manufacturers used the GB gearbox with the enclosed clutch arm, and there is some material out there on these boxes. This text is predominantly about the earlier BA box fitted to my Square Four, which shares much of it's internals with the GB, and indeed the GB was derived from it.The gearbox which is the subject of this article is a 1951 BA from a Mk1 Ariel Square Four.

There's an excellent video, by Alan Moore of the AOMCC, showing how the gearbox works:

Getting Access - Removing the Gearbox

Remove the clutch cable by loosening the adjuster and disconnecting the cable nipple from the clutch operating arm on the gearbox outer cover. If you have the rubber boot fitted over the arm, draw this back over the arm to expose the nipple.

Just imagine how that would have been handled in a Carry-On film. You can almost hear Sid laugh. 

Speedo Cable Screw - don't lose it!

The speedo cable is removed from the end of the gearbox by removing the screw on the outer casing beneath the cable. Put it back in once the cable is removed so you don't lose it.

Loosen the bolts securing the kick start lever and the gear lever. I leave the levers in place since it gives you something to hold when you remove the gearbox.

Remove the clutch cover, slacken and remove the spring screws and remove the plates. You now have access to the clutch centre tab washer which you can knock back, followed by the nut and the clutch centre. Next, drain the primary case and take out all the screws. Split the primary chain and put it in a bag to keep it clean. Now you can knock back the tab washer (in six places) securing the clutch basket screws. Remove the screws. When you lift the clutch basket away, arrange a plastic ping meal container underneath to catch the needle rollers within the centre bearing. Hopefully they won't all fall out. There are 12 of them.

On a Square Four, take off the oil tank and battery carrier to give greater accessibility to the top and bottom clamping and swivel bolts. On my W/NG you can get to the top bolts without removing the oil tank, but it's still easier if the tank is not there.

Lastly, remove the two rear chain guards and the rear half of the primary case. You can now see, and hopefully you will clean the gearbox.

Complete, vice mounted Burman BA

The gearbox is now ready to be removed from the frame. Loosen all rear engine plate bolts and the gearbox adjuster and allow the plates sufficient slackness to enable the gearbox to be lifted out towards the offside. Have a rest. I know your pride & joy looks like a basket case again doesn't it!

Clamp the gearbox in a vice by way of the bottom swivel lug and remove the nuts securing the outer end-cover, which can then be pulled away complete with the kickstarter and foot-change mechanism. This is what you will see:

CP Gearbox Kickstart & Selector Mechanism

We'll look at these bits later, or you can skip to the bottom of the text and look at them now, which is what I did!

An exploded gearbox. I hope his book is out of copyright.
The gearbox is of course upside down...

Dismantling the Gearbox Internal Mechanism

The kickstart pinion ratchet & pinion

This  operation can begin by unscrewing the hexagon nut on the end of the mainshaft and taking off the kick-starter driving ratchet, ratchet pinion, distance sleeve and short coil spring.

These parts require checking for wear, together with the kick-starter quadrant which was removed with the outer end-cover. You need to make sure that the teeth on the ratchet nut (item 41) and the driving ratchet (item 42) are nice and sharp, and not worn. You'll see them in a picture somewhere hereabouts, looking nicely unworn.

The mainshaft nut is a bit mangled though, looks like it has been in a scrap with Mr. Chisel & Mr. Hammer.

The, um, Key to Fig 33. Sorry Mr. Waller.

If the first few teeth of the quadrant are "burred," these should be ground down to give a clean engaging action with the ratchet, but a new part is, of course, advisable. Note that the first 'tooth' is typically ground off, which enables engagement with the pinion in the first few degrees of movement.

Kickstart quadrant. Perfect condition.

Remove the inner half gear-cover from the main casing, taking note of the twelve hardened rollers which form the bearing for the gearbox camshaft. Those of you with W/NGs will note that this roller-race has been replaced with a plain bush. Next remove the slotted screwed plug at the base of the main casing and pull out the pawl spring.

Pull out the mainshaft from the clutch side and then remove the layshaft with gears and operating forks as a complete assembly. This is not difficult, but to make it easier you can remove the mainshaft & layshaft third gears before you take the whole cluster out (items 15 and 45 in the exploded view). You can put them back separately too. Saves you dropping them on the floor and spending the rest of the evening in tears.

Inspecting Internals for Wear

The pinions and operating forks should be carefully examined, as should the layshaft and mainshaft. Check for wear on the fork operating faces and renew if at all grooved. Note the order of assembly on the camshaft and that the longer of the two forks is for operating the sliding gear clutch on the layshaft. Remove the split pins retaining the dowel in each fork and remove the dowel. Inspect the dowel for wear, which will appear as flats worn on the sides. Replace the dowel using new split pins, cutting them short & bending the legs outward. Grease the pins and the slots before you reassemble the camshaft.

Forks. Beautiful. Clean. Square. Lucky boy.

Burman gear pinions are not case-hardened, but being made from oil-toughened nickel-chrome steel, are hard enough to give strength and wearing quality without the risk of frequent fracture, which is more relative to gears which have been case-hardened and treated. Gear pinions very seldom call for replacement, unless through some reason a fractured tooth has occurred.

Of course, we are looking at gears that may have been in service for many more years than perhaps Mr. Waller might have imagined, so we might look more closely at our teeth. Always pays to take care of your teeth.

So what are we looking for? ISO 10825 lists a number of failure modes for gear teeth:

• surface disturbances such as wear, corrosion or overheating
• scuffing, which is the transfer of material from one surface to another, under load
• permanent deformation - bending, rippling, indentation
• surface fatigue, such as pitting, spalling or flaking
• fissures & cracks
• tooth breakage

Fortunately, examination of the gears revealed no damage and very little wear. Machining marks were evident in some areas. 

George had poor teeth...

If the gearbox has been long in service it is advisable to check both the layshaft and mainshaft spindles between lathe centres and using a clock-dial gauge.

If either shaft shows bending to have taken place and this to exceed 0.005 in., a renewal is advised. Test the shafts in their respective bearings or bushes and note that a clearance wear of 0.005 in. - 0.007 in. is permissible before renewal. The driving gear and sprocket, having been left in position in the gearbox shell, should be tested for clearance, both internally and externally, and if the centre bushes show a clearance exceeding 0.006 in. - 0.007 in. when tested with the mainshaft inserted, fit new ones.

Driving-Gear Bushes

Two are fitted with a centre space for grease deposit between the two and are a tight press fit and require reaming after fitting to give a shaft clearance of at least 0.0015 in - 0.002 in.

The contents of my box

To remove the driving gear from the casing the sprocket large locknut must be unscrewed. Some models have a special lock-washer securing the nut, whilst others incorporate the system of punching the inner edge of the nut into one or more of the splines of the driving-gear shank. Knock out, pry out or drill out the elements of the lock washer that are retaining the nut, and proceed with removing the sprocket.

To remove the sprocket, Mr. Waller says:

To hold the gear and sprocket from turning, a very useful tool can be made up and used as follows. Obtain a scrap mainshaft and grind two flats on the thick end which carries the clutch race . Fix this shaft in the vice by gripping the flats. Take the mainshaft sliding gear and place on the splined shaft with the large pinion uppermost. Next invert the gearbox case over the shaft and engage the sliding-gear pinion with the driving gear.

That method is all well & good when there are a plentiful supply of old mainshafts knocking around, but I don't think today I or anyone else will be destroying precious spares in this cavalier fashion. My alternative starts with removing the mainshaft, and inverting the whole box so that the sprocket nut can be gripped in the jaws of your vice. Then, take a large Stilson wrench/Monkey wrench/pipe wrench, and open it up as wide as you can. Use the Stilson to grip opposing teeth on opposite sides of the sprocket and turn the whole sprocket, which the vice grips the nut. You might need a tube or something to increase leverage - it will be tight. It's a normal RH thread, so when it won't come undone don't think you are tightening it!

Shh don't tell anyone, but this is a Bantam clutch puller!

Undo it using this method until it is free to turn, but don't forget that the box is supported on that nut. As soon as the nut is undone the box will fall on the floor if you don't watch it! Take it out of the vice and finish removing the nut with the box safe on the bench. The driving gear can pushed into the case for removal, when you strip the internals out.

The sprocket can be stiff too. A puller will fix that easily.

Gearbox Sleeve Gear Oil Seal

Seals in situ

During the 1948 season, Burman introduced a self-adjusting oil-seal to be fitted next to the main driving-gear ball bearing. The idea was to convert the gearbox to "all oil" lubrication from the grease or grease/oil mix used previously; although the seal was effective in preventing leakage at the bearing end of the box, there was considerable "weepage" elsewhere.


With a seal fitted it is advisable to use a fifty-fifty mixture of oil and grease as a lubricant and "top up"  with a grease gun filled with such a mixture.

The oil seal can be obtained and incorporated on any Burman four-speed gearbox, Type "BA" and Type "CP ". The seal fits with a thin steel gland washer on either side, immediately behind but after fitting the driving-gear bearing (see Part No. 25, Fig. 33). The seal components are shown in picture nearby.

Check the Main Ball Bearing and Bushes

The driving-gear ball bearing is easily pressed out of the housing after removal of the circlip and dust-cover, and the oil seal if it is fitted.

Wash out the bearing and check inner and outer races for pitting and wear. While you are at it, wash out the mainshaft ball bearing from the kickstart end and inspect that too

If bearing shows any signs of wear and "shake" renewal is advised. A worn bearing will cause gears jumping out as well as undue noise. Mine were both loose & showed a fair bit of play once clean - unwashed, they were just gritty & hard to move.

The layshaft spindle bush and camshaft bush fitted into the gearbox case should be examined. These bushes have a flanged-face fitting and are pressed into position.

BA Gearbox Sleeve Gear Seal Components

All the tolerances, plus the actual dimensions of the bushes and shafts from my box are on the Engine & Gearbox Tolerances page within this blog. You'll notice that my bushes are all on the upper end of acceptable wear, but considering that this machine will doubtless be used for leisure pursuits we will not replace the bushes this time.

If the camshaft bush flange is worn the shaft can take up a floating action due to excessive end-play, and as the operating forks are located on the shaft this float will readily cause the forks to over-travel with the sliding gears and disengage them whilst under load. A temporary repair can be effected by placing a hardened shim or washer on the end of the camshaft to compensate for the worn flange, taking care to leave at least 0.001 in. - 0.002 in. end-play.



The coil springs and their housing

After ensuring that all gear pinions and shafts are in good condition for further service, preparation should be made for reassembling the main gearbox. We will however review & inspect the gearchange & kickstart mechanisms first.

The Gearchange Mechanism

The foot gear-change mechanism is of the positive type and allows only one gear at a time to be engaged by one movement only of the pedal either way. Apart from accidental damage, the only parts requiring replacement due to wear and tear over a long period are the two main coil springs and the two pawl coil springs positioned in the alloy spring-box, and the ratchet and quadrant pawl.

Pawl and his teeth. Actually very good

The ratchet and pawl should be closely examined for any sign of wear at the engaging points and, although a temporary repair can be made by "stoning" up, these parts should be replaced if they appear to be unduly worn.

Check the tightness of the three rivets securing the ratchet and quadrant to the sector. Any slackness of this assembly will cause trouble in gear engagement and, resultant jumping out of mesh will occur. You'll see the three rivets in the adjacent picture - two round rivet heads on the arc with the gear teeth - the third is just visible as a circular mark on the pawl ratchet. This rivet is countersunk this side.

Note that in the same shot you can see the timing mark on the arc with the gear teeth - the small punched 'O'.

Three rivets & a ratchet

The Kick-starter

Hopefully you remembered to inspect the kickstarter quadrant when you took it out - if not, clean it and do it now. When you have it clean, pay close attention to the splines for the kickstart lever. If these look worn (i.e. they are not distinct sharp splines with parallel sides) go and find a new shaft. The shaft can be pressed out of the quadrant if need be.

The quadrant and ratchet having been examined or replaced, attention should be given to the kick-starter lever return spring. Ensure that the spring is strong enough to return the lever and pedal to the vertical position after being depressed. A weak spring can have its tension increased by rewinding a further one or two turns, or you could seek out a new one, or, if you fancy playing with your Rothenberger Superfire 2 you could reharden & temper the old one. No guarantees though, this is tricky work!

Kickstart Quadrant Stop (top left)

When refitting, do not wind the spring up solid, but only sufficient to throw the lever and pedal sharply to the normal vertical position. The inner end of the spring fits into one of the slots on the kick-starter shaft immediately behind the quadrant, and the outer end to a peg provided in the gearbox cover. The correct way for fitting the spring is for it to be located on the shaft with the coils running clockwise from the centre. If fitted the reverse way, the pedal will be thrown to the lowest position instead of to the top of the stroke.

The gearbox is fitted with a stop for the kickstart quadrant, which is akin to a Metalastik bush (a steel ring with a rubber centre) fitted over a peg, which is in turn a press fit in the middle casing. AOMCC wisdom suggests that it's installation restricts the kickstart movement some 20-30 degrees.

Reassembling Gearbox

Assemble the cluster on the bench

This is really a reversal of the dismantling operation, said Mr Haynes. Before you start however, prepare all the parts. Make sure everything, including your bench, is really clean. Clean off all that nasty red hermetite the previous bodger smeared everywhere. Clean the oxide off the cases with a wire brush, make it nice and shiny with a dose of elbow grease and save yourself a trip to the blaster. Make any repairs you need to make to the alloy parts of the case - repair that broken clutch cable lug, replace the missing kick start stop. 

New kickstart stop peg

Actually I cheated a bit here. I have never tried aluminium welding  (though there is an excellent site at www.mig-welding.co.uk to help you), so to deal with the broken clutch cable lug I bought a new middle casing - but this one had no kickstart stop. You might remember it from this post. Now, normally these are a press fit in the middle case, but mine was missing and the hole mis-shapen. The best option I had was to recut the hole with a 1/2" tap, and the only one I had was 20TPI. I had intended to make a new stop peg from a 1/2" BSC bolt, but since I couldn't find one I had to make a new one from 1/2" round bar, 1 1/2" long, and threaded 1/2" BSC for 1" of its length. I tapped the hole on the case, and cut a slot for a screwdriver in the threaded end of the stop to wind it in. I will secure it with Loctite when I have assembled the rest of the box.

Kickstart stop peg in place

Then replace any bushes that are too tired and ream them to size, not forgetting the tiny bush for the clutch arm. These like most bushes are a press fit in the clutch arm lug on the outer case. Remove them by pushing them out wit the new bush. with the aid of a small bolt (M5 fits neatly) drawing the old bush into a small socket. Clean out the shavings. Replace any missing Welch plugs from the drive sprocket end of the case. These are really easy to make from sheet steel, formed hot with a ball pein hammer in an old socket of a suitable size and deserve a post of their own, since I am running out of space for pictures here!

Lastly, fit the new ball bearings. This is made a lot easier if you leave the bearings in the freezer while you have your dinner. Make sure the seats for the bearings are spotless - you don't want any grit or swarf preventing the bearing from going into the proper position, otherwise they will not be supported properly and you won't get the oil seals in - there is not much space in the large bearing housing for the bearing, seal and the spacer discs. Heat each case with the trusty hot air gun and drop the cold bearings in, seating them with a suitable drift - don't touch the balls or the inner race with your drift, punch or hammer! A cold bearing in a hot case won't need much force, if any. Put a few drops of a bearing retainer (I use Loctite 603) around the outer race.

Now we can begin assembling the box.

Note the correct order of the driving-gear ball bearing, retaining rings, felt washer, etc. and assemble those parts. Grease the bearing as it goes in, and the oil seal if you have one and fit the spacer into it. Insert driving gear in the new bearing, fit the sprocket, the lock washer and do up the nut. You can tighten it but don't bend the lockwasher yet, until we are sure it doesn't need to come off again. I like to leave the nut loose until the box is fully assembled & tested, since it is a pain to tighten. You don't want to do it twice.

Knackered clutch arm bush

Make up the mainshaft gears, layshaft assembly, camshaft and operating forks into a complete sub-assembly, and insert this into the gearbox case, locating the layshaft and camshaft spindles in their respective bushings. It is easier if the camshaft pawl is off whilst replacing the cluster. Insert the mainshaft from the driving-side and pass it through the mainshaft sliding gear. Wiggle it a bit to get it through the splines.

Wiggle the cluster into the case

Fit  the remaining third mainshaft gear on to the shaft end. Check the proper position of the camshaft pawl and refit it, followed by the pawl spring and plug. Leave the plug a bit loose until you have the end cover on - it makes it easier to test for each gear when you are rotating the camshaft by hand.

Fill the roller groove at the end of the camshaft with grease, and place the twelve camshaft hardened rollers (where fitted) in the groove, sticking them in the grease, and fit the gearbox inner cover. 

Use Wellseal on the cover - there is no gasket. Nip up the 1/4" BSW nuts securely. Test mainshaft for end-play which should be 1/64 in. - 1/32 in. If end-play is excessive, this can be reduced by fitting a slightly longer ratchet pinion steel bush on which the kick-starter pinion and small coil spring fit. Another method for reducing end-play is to countersink the inner face of the shaft nut to allow it to project over the shoulder on the shaft end and so push the ratchet further along the shaft.

Refit kick-starter ratchet assembly and tighten mainshaft and nut. Turn the mainshaft to make certain it is free - I have nipped the kickstart pawl spring behind it's sleeve, which isn't obvious and puts a side load on both rolling bearings.

Timing Must be Checked

Add the 3rd gear pinions

Before you go any further, make sure you can select all the gears. Turn the camshaft using the quadrant - it can be a little stiff, but turn the mainshaft to help it along. You don't want to finish assembling the box only to find something amiss. Tighten the pawl spring plug when you are done. Dave Pitt from the AOMCC says:

"Going anticlockwise the 0 on the cam gear is at about 2 o'clock in 4th, 11 o'clock in 3rd, 8 o'clock in 2nd, between 5 & 6 in detented neutral, and about 4 o'clock in 1st. You can find an undetented neutral between 2nd and 3rd, and 3rd and 4th. The 0's align in undetented neutral between 2nd and 3rd."

Note that when finally fitting the foot-change assembly the quadrant and small gear pinion on the camshaft must be correctly "timed" or meshed, otherwise incorrect positioning of gears will result. The quadrant and pinion are marked with distinctive timing dots (the stamped 'O's) and these must be intermeshed when the gears are in the neutral position before finally bolting up the outer gearbox end cover. As Dave Pitt says, note that the 'neutral' referred to here is a false neutral, not detented by the pawl, between 2nd & 3rd, and is not the true neutral. The true neutral is a detented position on the camshaft between 1st & 2nd.

CP Gearbox with stamped 'O's' aligned

Gear Indicator

Refit the end cover - use Wellseal again on the joint, there is no gasket. Whilst the gearbox is still in the vice, make sure you can get all the gears. and make sure the kickstart returns the lever smartly to the top of its stroke.

You can now tighten the sprocket nut - fit an old clutch centre, with a bar through the  studs and you will be able to tighten the sprocket nut sufficiently. When you have finished heaving this about, you can refit the two gear indicator pointers and the clutch lever and it's adjusters.

A gearbox in a frame

Install the complete gearbox back in the frame. Fit the gear lever, kick start lever, and the clutch cable. Then check the engine plate nuts once more and fill the gearbox with grease/oil mix, enjoying the unprecedented access to the filler cap. The end cover as well as, of course, the main gearbox case should be nearly filled with any of the makers' recommended brands of grease mixed 50/50 with oil, or a self-leveling grease. Quantity required is about 600 ml. Do it up and re-fit the oil tank if you removed it. 

Fit the speedo cable, noting that it goes right down in the hole and that the screw slides into the annular groove in the cable end. If you don't get it in far enough, the cable inner appears mysteriously too short, but will intermittently drive the speedo...


Now you get to go around the other side and put the clutch back together!