Thursday, 23 March 2023

WELCOME to my blog about restoring (mainly) vintage overhead camshaft AJS motorcycles


I have just completed restoration of a 1933 AJS 33/7 Trophy Model (see here for the complete story) and waiting for some better weather before road testing.

However, I have no more OHC AJSs to restore and so I'm about to embark on the restoration of 2 early Velocette KTTs - specifically KTT 55 and KTT 305; this is the brochure picture of a Mk 1 KTT.

Acknowledgement for the above picture as stated

Further details of the actual bikes that I'm about to start work on can be found here

During the last couple of years I have posted quite a lot of information and to aid navigation the "Labels" section on the right side of this page lists the various projects.

The labels marked "INDEX" give a link to a page that provides a complete list and links to all of the separate sub-projects related to that main project.

Alternatively, scroll down this page and see what's here...

When I started this blog I already owned (and still own) a 500cc AJS R10

that I've been riding for many years and wanted an early 350cc bike. I bought one at a Bonhams auction; this is what I brought home....

....a bit of work was needed to bring it to back to life 

Full details of the restoration can be found here.

During the restoration of the K7 I figured that I could put an early overhead camshaft Velocette cylinder, cylinder head and cambox onto the crankcases of an AJS 350cc engine from 1931, convert it to chain-driven OHC and make an engine that looks like a K7 but has a Velocette top-end. I had a 1928 350cc AJS sidevalve that I had bought on eBay and used that to create the AJcette credit to both manufacturers.

It looks pretty similar to the K7 and to demonstrate that there really are 2 bikes, here they are both together.

Details of the AJcette project can be found here.

I have quite a lot of early Mk1 OHC Velocette parts and after completing the AJcette I decided to use some of these to make a replica of a one-off bike that AJS built in 1929/1930 for an attempt on the world speed record. The original is a huge V-Twin beast that started out with a naturally-aspirated engine but, having failed to gain the record, was supercharged ...and again failed. The bike ended up in Tasmania for many years and, after being repatriated to the UK and restored, it is now in the National Motorcycle Museum.

This is what the original looked like:

and this is my recreation.



Like the AJcette, the V-Twin uses Mk 1 OHC Velocette cylinder components. The full story of how this bike was built can be found in the links here.

There is also a 14 minute edited Youtube summary of how these bikes came about here and a longer unedited version here.

In January 2022 I started the restoration of a 1933 AJS Trophy Model

and I have just completed (March 2023) this bike:


The Index Page for this project can be found here.

I also reported on a couple of my other projects ....vintage OHV Nortons

 and putting a Marshall supercharger onto my 1934 MG PA


I hope you find something of interest.

Velocette KTT 55 and KTT 305: INDEX Page

This is the INDEX page for the restoration of 2 Velocette Motorcycles, KTT 55 and KTT 305

Velocette KTTs 55 and 305

Velocette KTTs 55 and 305

Now, I know that since it's inception when covid kicked off and I started documenting my projects this has been a blog (mainly) about early OHC AJSs and that the URL is but I’m now going to start on a couple of Velocette projects. Why? …you may ask. Well, quite simply, I have run out of OHC AJSs to restore and, whilst I have a couple of early AJS Big Ports that I acquired in bits and need reinvigorating, I have some early OHC Velocette projects that need attention and so, my apologies to anyone that has landed on this page expecting to see AJSs as I will be undertaking and reporting on 2 Velocette KTT restorations during the coming year.

During the last couple of decades of my working life I acquired 5 early OHC Velocette projects (people say that one should prepare for retirement) – 2x very early flat tank Model Ks, 2x KTTs (55 and 305) and another collection of bits that includes a KTP (a commercially and technically unsuccessful model that was produced to satisfy the fashion for twin-port engines although the twin-port cylinder head from this bike came in useful for the V-Twin  - see here) plus a couple of spare engines. With only one exception (KTT 305) all of these projects arrived as boxes of bits (I am not the type of enthusiast that buys complete bikes and takes them apart to populate shelves filled with rows of magnetos, carburettors, crankcases etc – a completely pointless exercise in my opinion ...but there are plenty that do!).

Anyway, I have decided to restore both KTTs simultaneously.

For reference, this is a 1930 brochure picture of a Velocette KTT.

Acknowledgement for the above picture as stated

I have been a member of the Velocette Owners Club for many years and in my opinion the Velo Club is one of the best clubs around with many enthusiastic and knowledgeable members and an excellent magazine (Fishtail) and spares scheme. GroveClassic Motorcycles also provides a range of spares for Velos, including various bits for the early OHC models.

There is probably more detailed history and technical information written about Velocettes than any other marque and I would recommend any/all of the following books to anyone that has an interest in their history.

First, a bit of background on the 2 KTTs that I plan to restore:

KTT 305

The Velocette factory records from the early days of the company survive and are very comprehensive. These show that KTT 305 was sent directly from the factory to the Isle of Man on 29th May 1931 for a rider by the name of Dave Brewster to compete in the 1931 Junior TT. I have checked the records myself

and also have confirmation from Ivan Rhodes (Ivan is THE Velocette guru). The bike still carries its original registration number OV 1023 as stated in the records.

I have 2 photos from that era; the first is with Dave Brewster pictured on the bike at the 1931 TT:

Picture courtesy of Dennis Quinlan

and the second at Parliament Square in Ramsay during the race:

Acknowledgement to whoever owns the copyright to this picture

Dave Brewster came a very creditable 18th in the Junior TT with an average speed of over 66 mph. Not bad considering the exalted company against which he was racing.

Dave was a top GP rider in Australia during the 1920s and won the Australian GP in 1924 on an Indian Chief

I have no idea what happened to KTT 305 for the 40-year period after its TT debut but it was raced competitively in the 1970/80s in Vintage Club events by a rider Barry Blythe. This is a picture of KTT 305 as I bought it (and as it is today in my garage) having been raced hard by Barry!


There are a few features of the bike as it is today that are period-incorrect, for example, the oil tank which should have the filler on the other side. Luckily, I acquired a correct KTT oil tank some years ago as I would like to restore the bike to how it left the factory.

KTT 55

I acquired KTT 55 in 2009 as a completely dismantled box of bits. The factory records show that KTT 55 was shipped to a dealer Martin Walter Ltd in Folkestone on 22nd March 1929 and subsequently sold to a C S Hutchins on the 26th March.

However, when I checked the frame number that came with the bike against the factory records, instead of being 2781 it was 3772.

The factory records show that this fits in with a series of KTT frames from1930

….but does not actually appear in the records. Ivan Rhodes suggested that it is probably a replacement frame, possibly following an accident, which would explain why it does not feature in the Velocette records.

There is another anomaly with the bits and pieces: whilst the crankcases, thick-flange cylinder barrel etc are all correct (and in excellent condition) the cylinder head, which on an early KTT should have been a cast iron item, is a later bronze head which would have been fitted to a Mk IV KTT and been produced in the period 1932 - 1934. The head is brand new – it has been machined but has never been used.

As all this occurred around 90 years ago one can only guess at what happened. My best guess would be that another frame was purchased from the factory following damage from an accident (as Ivan suggested) and, before the bike was repaired, the Mk IV came on the scene and the owner decided to update the bike with the latest cylinder head ….but the rebuild never actually happened and the collection of bits has somehow managed to stay together since that time.

I have already carried out some work on the engine of KTT 55 that I shall report on in due course. But, in the meantime, it is time to make a first and more detailed assessment and a top-down plan for each project.

Thursday, 16 March 2023

The AJS 33/7 Trophy Model Restoration: Final Assembly and First Start

It’s interesting how 10% of the time on the final assembly goes into putting 90% of the bike back together whilst 90% of the time seems to go into the remaining 10%.

The bike is now completed

and running, although road testing has not yet started.

There were a few details to attend to before the bike was completed, in particular: the toolbox, wiring and the tank graphics. 

The brochure picture of the bike clearly shows a toolbox sandwiched between the frame tubes:

Luckily, Mark Barker, who attends major autojumbles such as Kempton Park and Shepton Mallet here in the UK, makes beautifully crafted period leather toolboxes housed in metal and will make these to order if a bespoke size/shape is needed. With just a simple cardboard template (to ensure the angle was correct between the frame tubes) Mark made this for the 33/7:

The craftmanship is simply outstanding. Mark doesn’t have a web site but if you want anything similar then please let me know and I’ll put you in contact with him.

I haven’t said much, if anything, about the electrical system so far. I don’t intend and I doubt if any future owner would plan to undertake any extensive night-time travel on this bike. I have fitted lights and a horn (required by UK law) with a large capacity 12V lead-acid gel battery contained in a dummy rubber battery case. There is no charging system but I have used low power (but very bright!) LED bulbs and, as such, the lighting system is more than adequate for a few hours running if required.

The wiring loom is relatively simple – lights, horn and dipswitch and after making the basic loom

I sent this away to MES in Warwick to bind my collection of wires and connectors into a proper wiring loom.

Last, but by no means least, the petrol tank needed completing – painting and the “AJS” insignia. Although the depiction of the bike in the brochure gives some idea of the layout of the petrol tank graphics a picture of original paintwork is by far the best if one can be found. I believe that this picture

Picture courtesy of Bonhams

that can be found on this bike sold by Bonhams in 2008 is original unmolested paintwork.  OK, it is a 1935 500cc model but I believe that this is almost certainly identical to the 1933 350cc model.

The tank was masked appropriately

before spraying with 2k etch primer, gloss black and gold leaf lining plus a waterslide “AJS” insignia.

This is a picture of the completed bike.

After nearly 15 months of work, filling the oil tank/gearbox/primary chaincase with oil and a few final checks the bike was now ready to be taken off the stand and wheeled into the garden for a first attempt at starting.


…..and then the moment of truth!

I was amazed – the bike started at the first attempt and apart from some oil leakage from the primary chaincase (these pressed steel cases are notoriously difficult to seal) it ran perfectly; clearly, this needs to be fixed before the first road test.

The first road run will have to wait a while – it is the middle of March and although the daffodils are out in the garden the weather is neither warm nor particularly dry at the moment (I don’t do cold and wet motorcycling these days). Nevertheless, I’m confident that this will be a lovely bike to ride and I’ll report on further progress and the first road run in the coming weeks.

In the meantime, it’s time to start thinking about the next project….

Monday, 13 February 2023

The AJS 33/7 Trophy Model Restoration: Start of the Reassembly ...and Motorcycling in Kenya

The powder coating and chrome plating came back from their respective suppliers towards the end of January and work started on reassembly. However, I didn’t get far before my wife and I set off on a trip to Kenya that had been planned way back in 2022.

The trip involved safaris in 3 different national parks (Masai Mara, Lake Nakura and Amboseli, adjacent to Mt Kilimanjaro) and we spent quite a bit of time travelling by road between these. It is always interesting to observe motorcycling in different countries around the world; in most of Europe, the US and the Antipodes motorcycling is predominantly for pleasure and more often on large capacity bikes whereas, for example, in India or Kenya motorcycles are mostly smaller capacity “workhorses” and are used for transporting the family or goods around. Any visitor travelling on Indian roads will regularly come across a family of 5 astride a small TVS motorcycle.

I came across 3 interesting uses of motorcycle workhorses in Kenya. The first had a very substantial sheet metal folder strapped across the back seat, the second boasted a large 3-seater sofa across the back (I’m not sure whether the sofa was being transported or this was an up-market taxi service) and the third, and by the far the most impressive, was this one.

It is not so easy to see the bike under the Makuti thatching – the dried leaves of the coconut. As we drew alongside the rider is visible

and who just about manages a smile although the guy perched precariously on top doesn’t seem too happy

Looking through a few old pictures recently I also stumbled across this one from a trip to Vietnam.

 Before setting off for Kenya, I had managed to start reassembly of the bike.

The engine bottom-end was assembled and, together with the gearbox, was inserted into the frame.

The stem for the girder forks has also been attached with new 3/16” balls in the bearing cups.

The inner timing case is fixed and 3x 3/16” studs have been screwed into 3 of the 3/16” BSW threaded holes that support the cassette/bearing housing for the camshaft and magneto drive. The inner part of the cassette is a tight fit in the timing case housing and rather than trying to twist it into position later (and the same with the outer part of the cassette) it is much easier to use these studs to position it correctly on first assembly.

The bottom pivot for the cam chain blade tensioner has zero space on which to get a spanner or a socket and I tighten this using a machine chuck that is usually found in the lathe tailstock.

It is not possible to screw in the tension blade pivot and then insert the inner part of the cassette because part of the thread for the blade pivot is contained in the cassette itself.

Before completing this part of the assembly, the 20-tooth crankshaft pinion was mounted onto the keyed crankshaft.


The outer part of the cassette could now be assembled.

and all screws lock-wired.

It was now time to set up the valve timing. The 1933 OHC manual gives the following diagram for valve and ignition timing:

From this, I would discern the following:





Ignition: 500 BTDC fully advanced

Although both the inlet and exhaust periods are relatively short by modern standards, they are not unreasonable and in any case, I only have one camshaft and the only aspect that I can change is the phasing of the entire cam events.

I set a 0.010” tappet clearance and set crankshaft and camshaft at EVO (crankshaft with a degree marker disc and camshaft vernier adjuster position determined when clearance went to zero) to see what the other timing events would be. This gave measurements of:





These are remarkable close to those given in the manual and I decided to stay with this setting.

However, 500 BTDC for ignition timing is far too advanced by modern standards. One has to be careful in interpreting certain information given in manuals of the period and this applies to ignition timing. Why? Well, because fuels used in the 1920s and 1930s had quite different characteristics compared to fuels of today and the optimum engine settings were selected for the fuel that was available at the time.

The following graph gives a lot of insight into the evolution of fuels from the 1920s.

ref: A Historical Analysis of the Co-evolution of Gasoline Octane Number and Spark-Ignition Engines, Splitter,D., Pawloski, A. and Wagner, R. Front. Mech. Eng., 06 January 2016 Sec. Engine and Automotive Engineering

Although this graph is based on data from the US, the trends in Europe would have been similar. There are a number of points of interest that can be gleaned from this graph. Firstly, the red line shows that the fuel AKI (Anti Knock Index) or octane number increases steadily from a value of around 62 in the late 1920s to 90 in 1970 with a particularly steep increase in the 1930s and 1940s. This is extremely important in determining the maximum useable compression ratio and which, in turn, correspondingly increases from 4.5 to 9 over a 30-year period. (note: the US uses AKI = (RON + MON)/2 – the average of two different methods of measuring the octane number whereas Europe uses RON. RON is higher than MON. Nevertheless, the conclusions would be the same).

The purpose of this brief excursion into the evolution of fuel characteristics is to illustrate how this contributed to rapid engine development that occurred during the early days of the internal combustion engine …..and why 500 BTDC for ignition timing would have been OK in 1933 but not today.

I decided to set the timing at 380 BTDC fully advanced. With a compression ratio of 9:1 the engine may knock under low speed, high load conditions but with 30 degrees of manual retard available a good setting will be found and adjustments made if required.

2 new stand springs (I only had one) were made by Alberta Springs


and it took just a couple of days to get something that looked like a reassembled motorcycle.

The oil tank was rubbed down by hand and sprayed with 2k etch primer and 2 coats of gloss black. As I’ve probably mentioned before, I never send oil tanks out to be powder coated because of the risk of grit remaining in crevices inside the tank in spite of ones best efforts to mask every entry point prior to grit blasting and flush out every grit molecule when finished.

There are obviously a few more bits to bolt on and there is still a bit of work needed to finish the petrol tank – painting, gold leaf lining and the “AJS” insignia but the bike is now nearing completion.