Friday, 13 March 2026

WELCOME to my blog about restoring vintage overhead camshaft AJS and Velocette motorcycles

 

Apologies to anyone that has come to this page expecting to see exclusively vintage AJS motorcycles .....scroll down the page a bit and you will find plenty of them.

However, I recently sent all of my cammy AJSs to Bonhams and they were sold at the Autumn Stafford Sale

The URL of "vintageajs" for this blog is now somewhat misleading but it's too late to change it and there is still plenty to read about the AJAY projects. If you happen to be the new owner of one of the bikes that I recently sold then there is plenty here to read about its build. I still have 2 early Big Ports waiting in the wings ....but they will have to wait until I've completed the Velos. 

In 2023 I started the restoration of 2 early Velocette KTTs plus another Mk 1 OHC cammy special - a few details about each of these bikes can be found here and here

A lot of work has been done on these bikes over the past  2 ½ years and the INDEX PAGE provides links in chronological order of the project so far.

Earlier this year I acquired a DOHC 250 Velo Engine and now have a Resurrection Plan. The crankshaft has been rebuilt using MOV flywheels and "K" mainshafts, I have revised the lubrication system to mirror that of the Mk V KTT engine that is in my workshop, made eccentric studs to be able to fit the upper parts of the engine and, more recently, machined all of the cylinder head and cambox retaining studs and bolts. The cambox has been stripped, checked and reassembled and the engine build is now complete.

Links to all of the work done so far can be found on the DOHC 250 INDEX PAGE.

It's now back to the dry build of the bike and new engine plates have been made to install the engine into the frame. Details here.

During the last 5 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 owned 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 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 ....giving 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

This bike is now in the Sammy Miller Museum.

 

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

and this was completed in March 2023.

 

The Index Page for this project can be found here.

I also reported briefly 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.

The DOHC 250 Velo Project: Engine Plates

I was already aware that the engine would sit lower in the frame – see here – and having completed the engine build it was now time to install it properly. I’ve been making engine plates on-and-off for nearly 60 years – see here – and I would say it is one of those not-very-inspiring-but-necessary jobs without which a project such as this can’t progress.

The first job was to position the completed engine (minus carburettor, to avoid damaging it during installation) into the frame.

It has been positioned so that the top of the cambox is ~ ½” below the lower curved frame rail and is in pretty well the same place as when I first  tried it for size some months ago before the engine rebuild. Looking at the position of the holes in the original front engine plates that are fitted and those in the front frame lug the crankcase is about 11/16” lower than usual. The cable ties around the cambox and frame tube are to help position the top of the engine near on-centre as possible.

I have evolved a well-established routine for making engine plates, the first stage of which is to cut out a cardboard facsimile of the front engine plates,

mark the outline on a piece of 6mm thick steel plate (the steel plate used for these were left over pieces of scrap steel from making the plates for the AJS V-Twin and the 33/7 projects)

and cut it out with a plasma cutter.

The picture below shows the 2 plates before any cleanup.

After cleaning up the rough edge and finishing approximately to size using a flap disc on the angle grinder the 2 holes for the engine blots were drilled using an original engine plate to locate the centres accurately and then clamped to the frame

to locate and drill the other 2 holes. A centre drill inserted into the end of a 3/8” diameter steel rod

is used to start the holes.

The plates were then finished to size: there is one long straight edge on these plates and this was machined in the milling machine

before final profiling with a file.

The rear engine plates have been made in exactly the same way

and the engine is now firmly secured in the frame.

There will be another hole to put into the rear engine plates to secure the strengthening bar fitted to KTTs that ties together the engine plates with the rear lower frame section (part Nos. FK-167 and FK-167/2) to help avoid breakage of the lower frame lug and to mount the footrests and brake pedal but I have yet to make these parts.

One thing that I have noticed is that engines get heavier over the passage of time; I’m now 75 years old and although I don’t have any quantitative data to back this up, I'll swear that these engines weighed less 20 years ago.