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 completed work on revising 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, most recently, machined all of the cylinder head and cambox retaining studs and bolts - see here.

All of these fasteners have been chemically blacked in preparation for final assembly.

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 Engine: Securing the Cylinder Head and Cambox

Having completed the eccentric studs, the next step was to check the compression ratio – up to now I have had no means of bolting down the barrel and head properly.

The crankshaft assembly and piston + rings (the old rings – I have a new set but I’ll come on to that at a later date) were reassembled into the crankcases. The valves, without springs, were then inserted into the head and the head bolted down and checked for clearance at TDC. Plenty of clearance here - there would be no chance of the valves and piston making contact during the valve overlap period so the head was reassembled,

the piston was positioned at TDC

and with the engine held on its side with the spark plug hole uppermost, the combustion chamber space was filled with oil (R 40) from a burette.

The combustion chamber volume was measured to be 30.5cc which gives a compression ratio of slightly over 9:1. My guess is that this is probably around the value of when the engine was originally built and, although fairly high, should be OK with modern 98 RON pump fuel.

The next step was to determine the dimensions of the cylinder head studs, which also provide pillars for the cambox, and the cambox securing bolts. Like the eccentric studs for the cylinder, these were made in EN24 steel for strength and took quite a few hours of machining, for example, the 2 long bolts on the drive side of the cambox

and milling multiple hexagons.

Anyway, they all worked out well and the cylinder head and cambox fitted perfectly.

At this stage, I had intentionally left excess material on the studs/pillars so that there was a gap between the valve pushers in the cambox and the valves.

The height of the studs was then reduced to give a running clearance between the pushers and the valve stems with the cambox seating properly on its 4 contact points. I have set the clearances to 0.020” on the exhaust and 0.012” on the inlet. With care, I am hoping to build this part of the engine without resorting to shimming.

The final step was to chemically black all the bolts and studs ready for final assembly.