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 ran out of OHC AJSs to restore and I'm now working on early cammy Velocettes.

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. 

Quite a lot of work has been done on these bikes over the past 20 months and the INDEX PAGE provides links in chronological order of the project so far.

I have 3 rolling chassis up together - see here - and have been working on many smaller details - saddles, tanks, steering dampers, steering locks etc. The work on the chassis is, at least for the moment, complete and I've finished rebuilding clutches, gearboxes and positive stops.

Over the recent Christmas period I have started on the engines. So far, I have been rebuilding various sub-assemblies - crankshaft shock absorbers, cylinder heads (see here) and, most recently, making a new cam.  

I have started on rebuilding the cambox for KTT 55 and the first step has been to repair an existing casting with a gaping hole

back into something that resembles the original.

Details here.

During the last 4 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 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.

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.

Rebuilding KTT 55s Cambox – Part 1: Repairing the Cambox Casting

The cambox that came with KTT 55 had been substantially modified because the bike came with a bronze head (which should be fitted to a later Mk IV) and, because a bronze head requires a different cambox casting, someone in the past had modified an earlier cambox to fit. Anyway, I had parted company with the bronze head and modified cambox to a buddy that has a Mk IV fitted with an iron head and can make better use of it. I had already rebuilt an iron head (see here) for KTT 55 and now it was time to rebuild the cambox.

There are a lot of details to pay attention to in a Velo cambox. The picture below shows the bits that need to be assembled to make a functioning cambox – but it’s not just a simple matter of bolting them together and expecting it to work, at least, not when assembling a cambox from a collection of parts.

 

Many of these early cammy Velo camboxes have structurally damaged castings, usually to either one or other of the lugs at the bottom where they bolt onto the cylinder head studs or the section between the holes where the rocker skids enter to contact the cam – the latter can be seen in the cambox in the above picture where the thin “bridge” has disappeared. The other damage that is often found is to the 2BA threads that fix the bevel drive casting or at the other bearing-end of the camshaft. The above cambox also has some damage to the corner when the exhaust rocker exits.

Anyway, I decided that I would repair another cambox that was structurally intact (regarding lugs and threads) except for a gaping and jagged hole where the rockers enter the cam chamber.

Apart from the obvious unsightliness of the damage, the question arises: why repair it – after all, it’s hidden inside the cambox? The reason, quite simply, is that oil “escapes” from the cam chamber – thrown out by the rotating cam - into (and over the top of) the gutters on both sides of the chamber ….and then to the outside world and invariably ends up covering the bike. For this reason, the gap that connects the cam chamber and the cambox through which oil can escape needs to be minimised – 2 small holes in the original design. For anyone that has read my previous blogs, I have had plenty of experience in trying to solve this problem on the AJcette and the AJS V-Twin, both of which use the same cambox.

The first step in making a repair was to machine a piece of solid Aluminium into an annulus,

clean up and remove the jagged edges from the casting and mark out, as best as possible, the shape of the hole on the new piece of aluminium (by inserting it inside),

chop off the top section of the annulus and cut out the shape to fit the hole

and with support from a piece of thin steel bent to fit inside the cam chamber

use oxy-acetylene and Lumiweld to fix the new piece in place.

This was then cleaned up on the milling machine

and finished by hand with a file and Dremel.

After vapour blasting

…..not perfect, but a reasonable repair to the damage.