Tuesday, 20 July 2021

The AJS V-Twin Petrol Tank ….and Petrol Tanks from India

The petrol tank is obviously an important functional part of any motorcycle but it is also a key feature of the appearance and character of the bike. If you look closely at the pictures of the original AJS V-Twin record attempt bike it has a long, wedge-shaped tank – like a slice of cheese and any recreation of this bike should at least approximate this shape.

However, I have developed a somewhat ambivalent relationship with petrol tanks over the years: I love them when they look right and don’t leak and hate them when the converse applies. As I have mentioned in previous blogs, I am not a sheet metal worker. I managed to make the oil tank but that really is the limit of my sheet metal expertise and so this necessitates someone else making a tank for this bike. Before I embark on the saga of this AJS tank and the route I have followed a bit of background is required.

Some years ago I restored an early Ariel V-Twin. I bought this from Andy Tiernan, whom I have got to know quite well over the years, and started on the restoration. The picture below shows the bike “as received”

I always like a challenge!

Unfortunately the lovely petrol tank resting in the frame tubes is not the correct tank for this bike; the correct tank is the rusty one in the foreground.  Not surprisingly, this bike was a lot of work – one picture below from the dry build.

and eventually the bike was finished – here it is in my garden



Apart from building the wheels (Steve at Wheelwise does that) and making the petrol tank the entire restoration was done in my workshop ....and took me quite a long time.

The petrol tank caused me more grief than any other part of the project! I started by having a local retired patternmaker reconstruct the tank in wood, based on the rusty remains of the tank that came with the bike, to be used as a former. I then selected a small engineering company in Biggleswade who advertised sheet metalwork and who said they could make the tank; they told me it would take 2 – 3 months. They were provided with the original rusty tank (for the fittings), the wooden former of the whole tank and a cardboard template for the underside bolting pattern.

Well, in spite of constant phone calls every month or so after the stated completion time, the promised 2 – 3 months stretched to a year. After a year and as it seemed that fabrication of the new tank hadn’t even been started I called (yet again!) and said I would take my pattern and the original tank away go elsewhere. Amazingly, 2 weeks later, I received a call saying that the tank was finished and so I drove up to pick it up. Sure enough, the tank was finished and in spite of the facts that it had taken over a year, cost me 1,100 GBP (cash!) and weighed nearly as much as the crankshaft for the AJS V-Twin I was relieved to have the tank at long last. I was told that the tank had been sealed with ethanol-proof sealant from the US and had been pressure tested.

I duly painted and lined the tank and put it on the bike. When I first started the bike – and it started straight away, probably for the first time in 50+ years, it ran very well. Here is the first run from my drive up the road.


However, all was not well in the tank! After a couple of weeks, bubbles started to appear in the paint and, in the next few weeks,  the number of locations of bubbling paint grew and it soon became obvious that petrol was seeping through joints all over the place and that the tank would have to be stripped of paint, all the leaks found, resealed and then repainted and lined. I was not a happy bunny!

The first step was to get the existing so-called sealant out of the tank. For anyone that has done this you will know that this is not a pleasant or easy process to make sure that all the sealant is removed from every crevice inside the tank, especially when there is thick sealant that has solidified in corners. It also involves nasty chemicals, such as methylene chloride.

I tried shaking nuts and bolts inside the tank to dislodge the sealant out of the corners but could see that this simply wasn’t working. Eventually, I resorted to hiring a concrete mixer for the weekend and leaving the tank in the mixer for many hours with handfuls of nuts and bolts to try and remove the residual sealant.


I don’t know if I was successful in removing all the sealant but, as soft solder had been used in large amounts to fill in the significant gaps between the separate pieces of metal that had been used to fabricate the tank, I had no option but to remake these joints carefully with soft solder – brazing or welding was not an option. I also used sealant on the inside of the tank in the hope that both palliative measures might provide a seal and then resprayed and relined the tank (again!) and sold the bike at a Bonhams auction. If the eventual buyer of this bike finds that it still leaks, in mitigation, I can only say that I have done my best.

My first foray into Indian made petrol tanks started shortly after this debacle. I was travelling to India quite frequently in the early 2000s and, as I was in the automotive business and two of my major customers were motorcycle manufacturers, Bajaj and TVS, I asked the guys at TVS in Bangalore if they knew anyone locally that could make a one-off petrol tank. They put me in touch with a Mr Sridhar and I duly visited Mr Sridhar in the back streets of Bangalore and discussed this with him.

On my next visit to Bangalore I took with me a damaged tank from a Mk 1 OHC Model K Velocette as a pattern plus all the taps and dies for cutting UK threads to make the fittings and he duly got started. BTW, never ever mention to an airline that you have a petrol tank in your checked bag; even if last saw petrol 50 years previously or had never seen petrol at all! They get really unhappy. They also get really unhappy if you try and take a chainsaw on the plane, even in a checked bag that will go in the hold …but that’s another story.

Admittedly it took Mr Sridhar a bit longer than the 2 months he originally told me and the price increased a bit but within a few months he had made me 2 beautiful petrol tanks and oil tanks including all the fittings for a very reasonable price. After that, I commissioned a number of further Velocette tanks. Here is picture of Mr Sridhar and myself in front of his workshop with 2 Velo tanks in the making.

The workmanship is outstanding and how he managed to make these with only the most basic tools is a mystery to me.

The picture below, which I took last week, shows some of these tanks in my workshop awaiting their turn to adorn various yet-to-be-restored Velocettes.

After retiring in 2015, carrying tanks to and from India to have them copied was no longer an option and for the AJS K7 restoration and the AJcette I used a guy here in the UK. He had an original to copy and made 2 pretty decent replicas of the original rusted tank although I had to make all the fittings. He has now retired so that is no longer an option.

When I restored the 1929 Norton (see Vintage Nortons) I bought my first Indian petrol tank on ebay and it cost me about 200 GBP. There was no piecrust on the bottom (although I added that to give the correct cosmetic appearance) and it was about 1” shorter than the original but it was a pretty good replica and was well made.

And so, when it came to sourcing a petrol tank for the AJS V-Twin I had essentially 3 options: 1) make one myself; 2) Find someone here in the UK that would make one or 3) Source one from India that is a close as possible to the desired shape.

1)  Was not an option – I am really not a sheet metalworker.

2)  I tried various establishments that purport to doing this kind of project here in the UK but could find nobody willing to take it on. One supposedly reputable sheet metal fabricator specialising in classic bikes and cars couldn’t even be bothered to reply.

3)  If I was going to source a tank in India it would need to be either one that is sold on ebay or, if possible, to find one that is sold on ebay and ask for modifications; I chose this route.

I had shown the picture of the original AJS V-Twin with the long wedge-shaped tank to a good friend of mine and he mentioned that the early Ariel Model G tank has a shape that is not dissimilar – he has one of these bikes in his shed. However, there are some major differences in the construction – the Model G tank has a filler cap hole that is peculiar to a large Ariel filler cap and there are holes for a speedo and an oil pressure gauge but the shape is otherwise as close as one would hope to find from tanks that are actually being made.

I messaged one of the Indian ebay sellers about making one of these without the oil pressure gauge and speedo holes but got no reply. I then tried another seller that goes under the ebay name of vintagewheeles and got an instant reply.  I then sent a concise list of written instructions and modified screen shots of the original item on ebay, as shown below


They listed the tank on ebay as a “special” and with the pictures that I had sent them, I bought it….and about 5 weeks later a tank made exactly to my specifications arrived at my house here in the UK.

This tank was well made but not exactly what I needed for the bike (but that was my fault, not theirs) – it was a bit too short and I didn’t really want the large Ariel filler cap hole and so I commissioned another tank using exactly the same method of communication that was 3” longer, used the early Norton/Velocette type of filler neck, the petrol tap union moved to the middle and no paint.

A few weeks later the second tank arrived – and this was even in the middle of the bad Covid outbreak in India. The picture below shows both tanks that I commissioned

The upper one in the picture is the first tank and the lower one is the actual tank that I will use on the bike.

And the picture below shows the tank plus a seat resting on the bike to get a first impression of how the bike will look.


This was a moment for celebration. Whilst I have no qualms about making casting patterns, machining crankcase and timing case castings, cutting and heat treating gears or even making the entire crankshaft, getting a petrol tank that is the shape and quality that I wanted was always a concern.

And so, I have ended up with an extremely well fabricated welded tank in the correct gauge steel, exactly the shape and features that I asked for and for a total cost (excluding the first tank that I had made …that will end up at an autojumble) of around 500 GBP. I would regard this as pretty good value for a quality made custom tank.

If I compare this to what I have received and paid in the past for petrol tanks I will not hesitate to get further tanks made in India.

Footnote: I have a couple of “mates” that criticize Indian-made petrol tanks. Interestingly, when asked exactly what bad experience they have had it turns out they have no direct experience of either buying or using any petrol tanks from India ….it’s something they heard …somewhere. I have given what I believe to be an objective assessment and my actual experience. Make of it what you will.

Friday, 9 July 2021

The Exhaust System

New exhaust rings had already been made in AB2 Ni Al  Bronze but the exhaust pipes themselves needed fabricating.

Pipecraft in Lancing have previously made the exhaust pipes for both the AJcette and the AJS K7 (BTW, that is Lancing on the South Coast of England – not Lancing, Mi if you happen to be reading this in the US) and did a great job. However, I anticipated that the exhaust for the V-Twin would be quite a bit more complicated and decided that I would fabricated it myself using bends provided by Pipecraft.

Why should the V-Twin be more complicated? Well, there are 2 reasons for this: firstly, on the front cylinder, there is inadequate space to have a simple single curvature pipe and the pipe would need to wrap around the side of the timing case to avoid the front mudguard; secondly, on the rear cylinder, the exhaust port is angled upwards (because of the 25 degree-from-vertical angle of orientation of the cylinder) and this would require an initial bend of high curvature to bring the pipe downwards and inwards.

Before any work could start on the pipes themselves, stubs were turned on the lathe onto which the pipes would be secured at the exhaust port. The pipes to be used are 1.75” OD and 2mm wall thickness.



As with the copper oil pipes, wire patterns were made to follow the line of each pipe. However, there are 2 differences here: the first is that formers for bending the pipes are in a number of fixed sized radii – 175mm, 133mm, 114mm and 84mm and the design must be based on these specific radii; the second difference is that, because the exhaust pipe is of much larger diameter, the wire pattern needs to follow the centreline of the pipe. With small diameter copper pipe these considerations are not important because, although a small pipe bender is used, adjustments by hand are easy.

Partial circles with these fixed radii were marked out on a large sheet of paper and the wire formers were then bent by hand to the desired exhaust pipe shape and with the constraint of using only the allowable radii.


The pieces of masking tape stuck on the wire in various places indicate each bend radius.

Pipecraft then provided a selection of bends and, of course, straight sections from which I could then cut-and-shut the exhaust in situ.


The plan was to make each exhaust pipe in 2 sections – the first part containing the bends and the second the long straight section. Each end of the straight section was therefore swaged to allow it to fit over the front section.


In the above picture, the lower pipe is “as received” and the upper is after cutting the swaged section to length.

I know that some people will find this ridiculous, but the cuts that are necessary in the swaged end to allow it to close up properly on the inside pipe when clamped have been made with a 3/64” slitting saw on the milling machine rather than just cut with a hacksaw.

Why? Well because doing it this way I can guarantee that the cuts will be perfectly parallel to the axis of the pipe, they will be the same length and they will be at 900 to each other. And it only takes a few minutes to set up on the milling machine and do it properly.

The bends were cut and set up for the front cylinder first. In the 2 pictures below there are 3 sections forming the complete bend: the first section is held firmly in place as a tight fit on the exhaust stub; the last section is held by large magnetic V-blocks and the middle section is simply sandwiched between the other two.



The next stage is to very gently tack weld the sections together with the TIG welder and then remove the pipe and complete the welds.

I’m sure a trained welder would throw up their hands in horror at my welding …but then I’m not a trained welder. After cleaning up the welds the pipe is refitted to check.


Everything seems to have ended up in the right place. The pipe has not yet been welded to the exhaust stub; that will be done when the straight section is added.

After a repeat performance on the other side of the bike for the rear cylinder (also using 3 curved sections) the straight sections are cut to length and checked for position.



Adjustments were made to ensure that the pipes were parallel to the longitudinal axis of the bike, the same height at exit and the same distance from the frame before tack welding the pipes to the exhaust stubs. Brackets were then made to support the pipes at the ends of both the front and straight sections.  A couple of bespoke copper washers for the exhaust stub/port junction were laser cut by lasermaster

to complete the installation



….and enough bits left over to make a giant French Horn


Many Thanks to Andy at Pipecraft for providing all the necessary pipework.