Monday, 30 August 2021

The Final Build of the AJS V-Twin: Part 1

At this point, the bike was in a thousand pieces and scattered around various boxes in the workshop; it was time to apply whatever form of metal finishing was to be used on each part. First, an inventory was prepared for the bits and pieces to be outsourced for powder coating and plating – I always provide a list of the bits that are delivered as it’s much easier to check later that everything has been returned …or went missing!

Every bike that I have restored in recent years has been pre-1930 and for which nickel plating is appropriate. However, this bike is on the cusp of the nickel-to-chrome transition and I had decided that chrome plating would be more appropriate. Anyone that has read my previous blogs will be aware that I send the large items out to plating specialists (because they don’t fit in a 10l bucket of electrolyte) and plate all of the smaller components myself.

The petrol tank, exhaust pipes, handlebars and a couple of other bits were driven up to Castle ChromePlating in Dudley. I have used Castle Chrome in the past for nickel plating some of the parts on the Ariel V-Twin that I restored some years ago and the quality of the work was superb. At the time of writing this particular blog the parts are still with them ….so I’ll report progress in due course.

However, for the smaller parts that I intended to plate myself, I have only ever done nickel plating at home …so how to do chrome plating? It turns out that chrome plating in the home workshop in the same way that professional platers use is not an option because the chemicals used are pretty toxic. However, alternative processes have been developed that approximate chrome plating and are less dangerous for the amateur plater.

I chose to use Bright Zinc Plating which involves depositing zinc on the surface electrolytically followed by a passivation stage. Passivation is a chromate conversion process that involves dipping the zinc plated component into a liquid that converts the zinc into a mixture of zinc chromates, chromic oxides and zinc oxides and provides both a harder surface and, when polished, gives a reasonable resemblance to chrome plating. I had bought a Bright Zinc Plating kit from Frosts some years ago that I had not used up to now; I’m pretty sure that this is the equivalent kit that is now on sale and using what is referred to as the blue passivate.

But, first to experiment with the zinc plating process itself. I set up the plating bath in the same way that I have used for nickel plating and with an aquarium heater and air supply (to disperse bubbles that are formed on the surface of the item being plated) and put in a ~4’’ long section of copper tube. After a few hours I removed the tube from the plating bath to check on progress; one side of the tube had plated fairly uniformly

but the other side had a very thick and cratered deposit

Not a good start. And this was using the lowest voltage setting.

As the thick deposit was mainly on one side I checked that both the zinc anodes were connected properly, which they were. After a bit of research, I decided that for the next attempt I would remove the aquarium heater to reduce the temperature of the electrolyte. That made a huge difference and after a bit more experimentation I started plating the 17 lengths of copper pipe and the numerous brass fittings for the lubrication system. 

This proved to be quite a long and tedious job as each part has to be polished and then thoroughly scoured with abrasive paste using a toothbrush prior to plating and then carefully polished after the passivation stage. Although a packet of abrasive powder comes with the kit it is nowhere near sufficient and I use VIM, usually associated with cleaning baths and sinks in days gone by; it works extremely well and is a cheap alternative.  Polishing has to be done very carefully to avoid bending these small bore copper pipes out of shape.

As with nickel plating, I found that plating copper and steel parts to be straightforward but the plating on brass ends up thinner and it is too easy to polish through the passivated zinc layer and expose the brass below. It seems that the professional way of plating brass, which is an alloy of copper and zinc and not so easily plated, is to use a cyanide-based process but this is not an option for the amateur plater in a home workshop.

It took about 3 weeks to plate and polish all the pipes and fittings but eventually I had a box full of shiny silver-looking bits rather than copper and brass bits.

In the meantime, the powder coated parts had been finished and it was time to start reassembling the bike. I always like to get a rolling chassis built up as soon as possible as all the other bits effectively “hang off” of that. In addition to the new fork spindles and the repair to the steering head stem I also had new friction disks cut for the forks and steering damper – one on each side for the forks and one at the base of the bottom yoke for the steering damper. As I use the same company (Saftek) for all my friction materials, including clutch and brakes, I had the rear brake shoes relined at the same time. The front had already been done.

The front forks could now be reassembled and attached to the frame. I always use new ball bearings when reassembling steering heads (or any other ball race with lose balls); for the small amount of money that they cost it’s really not worth reusing the old ones. Mixing old and new balls is a definite NO as there is likely to be a slight difference in size as the older balls will have worn slightly.

The rear frame section was loosely attached at the same time and the engine plates put in place. The next job will be to put the "bottom-end" in the engine plates. The engine will be built in-situ in the frame rather than as a single entity and then “inserted” into the frame. Why? Well, there are 2 reasons: firstly, apart from 2 studs at the bottom of the crankcases, the remaining 6 (3 at the front and 3 at the rear) are sandwiched between engine plates and to ensure that the crankcases-to-crankcase seal is not broken after assembly it is better to assemble and seal the crankcases and to immediately put them into the frame and bolt up securely; secondly, the entire engine is pretty heavy and I don’t fancy trying to put it into the frame in one lump without injuring myself.

Up to this point, the crankshaft has not yet been put into the crankcases and I have relied on measurements that it will fit correctly. Before putting the assembled and sealed bottom-end into the frame various checks need to be made to ensure that everything - the crankshaft, crankcases, pistons + cylinders - actually fit together as intended.


Monday, 16 August 2021

The Last Jobs before Rebuilding

Up to this point in the project I had not made a list of jobs to be done ….simply because there was always so much to do that the list would fill a book. However, at this stage, where all that could be done with the bike in one piece at the end of the dry build and immediately before stripping it into a thousand separate parts, I made a list of outstanding jobs. Many of these are quite small but there are still a few mini projects that need attending to.

But first, the bike needs stripping. It took me 2 years to build it and 2 days to strip it and put it into boxes!



I divide the parts up into 4 boxes:

1)    Parts that need no further attention

 2)    Parts for powder coating

 3)    Parts for outsourced plating

 4)    Parts that need some further attention of some kind ….whatever that may be

I also put small pieces into plastic bags and label those that could be confused with some other part during the final build. This is particularly important for things like nuts and bolts – it may be obvious what it is at the time of dismantling but may not be so apparent when it’s time to reassemble a few weeks later.

This was the first opportunity to check the front forks in detail. The forks were only loosely assembled on the bike and the forks blades themselves appeared to be in excellent condition – no signs of damage and no rust. I expected to have to replace the spindles, because of wear, as a matter of course but one thing that I did not expect to find was this:

The main fork stem on the bottom yoke had been crudely welded in the middle and by poking around through the stem with a screwdriver and shining a light through the centre it was apparent that it had been welded all the way around and all the way through. The top section with the thread hadn’t even been attached on-centre! It is not so easy to see by eye but the stem was actually banana-shaped. The only reason that I can think of why someone would do this is because the top thread was stripped and so a top section from another set of forks was welded on to replace the original. I can’t think of any kind of accident that would do this but not also do irreparable damage to the fork girders and the frame.

…..and so to the repair.

The fork stem is 1.125” OD and a length of EN24T of this size was acquired, the thread was screwcut on the lathe and finished with a thread chaser to fit the original (and in good condition) top nut, and the bottom section was shouldered to fit inside the existing stem with a 1.5” insertion length. The centre of the new top section is bored to give an ID = 9/16” at the lower part and ID = 13/16” at the upper part. After cutting off the welded-on top section, the remaining part of the existing stem was faced off and reamed to give a uniform hole and the new top section was pressed in with a 0.0015’’ interference fit.

 After pressing in, the joint was silver soldered and 2x 3/16” pins were inserted and also silver soldered in place. You can just see the join line of silver solder and the outline of one of the pins below it.

I really don’t understand why people that do these repairs don’t make some attempt do it properly in the first place. The original stem is 1/8” wall thickness and the ID = 7/8”. Even if someone isn’t prepared to go to the trouble that I have to repair this, why not insert a 2” length of 7/8” OD tube through the middle of both sections before welding? Simple enough. At least both parts of the stem would have been in alignment.

Anyway, job done and now on to the spindles.

Not surprisingly, there was enough wear of the spindles in the girder to warrant replacement. The original spindles that I removed had already been plated (and the plating was peeling off!) and were sufficiently undersize at 0.430” (should be 7/16” = 0.4375”) to give more than enough undesirable play. The spindles that I removed were the original AJS parts fitted 90 years ago. How do I know? Well, AJS actually went to the trouble of putting their name on the bolt heads! In the picture below you can make out the AJS insignia on the flat of the hexagon.

I have also discovered in the past that these are not, in fact, bolts but spindles with a hexagon attached to make them look like bolts. On a little AJS 350 that I restored some years ago I found that the head of the “bolt” can be easily detached by inadvertently screwing it off the spindle if the spindle is seized in the girders. This is clearly a bit of production engineering economy that AJS used to avoid a lot of machining.

I have replaced girder fork spindles on many bikes in the past using EN16T round bar of the appropriate size and then put nuts and/or milled a square on the end to substitute for a hexagon bolt.

However, I haven’t replaced any spindles for a couple of years as I have been engaged in this project. In the past, I had found only one supplier, Mallard Metals, for 7/16” diameter round bar in EN16T steel, my preferred high tensile alloy steel for these parts. I also found that I had nowhere near sufficient in my “store” to make 4 new spindles and would need to buy some more. The Mallard Metals husband (Bob) and wife team would be at every autojumble in the UK and I got to know them quite well over the years. Sadly, I found that Bob died in March 2020 and Mallard Metals is no longer trading.

I then spent many fruitless hours searching for this steel but eventually stumbled across one supplier that actually stocked it. Unfortunately they are an industrial supplier (and steel manufacturer) and this meant that I had to order it in an industrial size, namely 3m lengths. The price dropped considerably for 2 lengths and so, in due course, 2x 3m lengths of 7/16” diameter EN16T arrived.

This will last me until the end of my days and should be more than sufficient to re-spindle every one of my yet-to-be-restored projects.

Unfortunately, something else came my way at the same time. If you do a Covid-19 test at home this is not what you want to see!


Having spent the last year and a half studiously avoiding this bloody disease it has eventually caught up with me. And I thought the waking-up fuzzy head was due to a little over-indulgence on the red wine the night before.

I had already had 2 AZ inoculations many months ago and it would seem that these really do work in ameliorating the symptoms. One week later and my symptoms are similar to a mild cold or very mild dose of flu. I can still manage 6 hours a day in the workshop without a problem ….so back to girder forks.

I made 4 new spindles, shown below, and these will be fitted with a pair of half-nuts as locknuts on the bolt-head end.

This is tough steel to machine and to get a good and well-fitting thread I use 2 dies; I first run a slightly worn HSS die down the thread length to remove most of the metal followed by a nearly new die to finish the thread. Trefolex cutting paste is used to lubricate the threading.

Apart from making a couple of keys – one for the crankshaft pinion for the camshaft drive and another for the clutch the metal cutting for the project is now essentially complete.