1935 AJS V4 Replica
Engine: 495cc air-cooled SOHC 50-degree V4, 50mm x 63mm bore and stroke, 10:1 compression ratio, 40hp @ 6,000rpm (est.)
Carburetion: Two Amal with dual remote floats
Transmission: 4-speed, chain final drive
Electrics: 6v, DC generator, dual twin-spark magneto ignition
Frame/wheelbase: AJS “Denly” single downtube steel frame/55in (1,397mm)
Suspension: Girder fork front, rigid rear
Brakes: SLS drum front and rear
Tires: 100/90 x 19in front, 100/90 x 18in rear
Weight: 450lb (205kg)
Seat height: 29in (737mm)
Fuel capacity/MPG: 5gal (19ltr)/NA

The word “unique” has a simple meaning: it means there’s only one of a kind. Things can’t be “quite unique” or “almost unique.” Either they are or they aren’t. Take Dan Smith’s AJS V4. It’s unique. There’s only one. And that’s because Dan built it himself.

Many of us can turn a wrench to do basic bike maintenance. Some of us are capable of restoring a rusty barn find to its original state, perhaps even making parts where the originals no longer exist. But very few of us can build a complete motorcycle engine from bare metal.

With the aid of drawings, a capable machinist could probably shape the parts from billet using CAD and a CNC mill. But what if there were no drawings, or even a model to work from? That didn’t stop Dan, who designed, cast, machined and assembled his V4 from a black-and-white period photograph and a cutaway sketch of the 1936 prototype. Oh, and if you didn’t know AJS built an air-cooled V-4, you’re not alone!

A little AJS V4 background
The Wolverhampton firm of A.J. Stevens earned a solid sporting reputation during the 1920s with their racing “Big Port” 350cc singles, while also building sturdy side-valve V-twins for sidecar use.

Unfortunately, the financial collapse of 1929 scuttled AJS, and the rival Collier Brothers of Plumstead, London, makers of Matchless motorcycles, snapped them up. Though they had a sporting reputation of their own (a Matchless won the single-cylinder class in the first Isle of Man TT race in 1907), the Colliers intended to exploit AJS’s racing heritage, hence the motorcycle that was the sensation of the 1935 Earls Court show in London: a Bert Collier designed air-cooled overhead cam V4 dressed in AJS livery. It was displayed with lights and generator as a fast road model, but exposed “hairpin” valve springs and space for a supercharger suggested it might be raced too.

The four cylinders were arranged in a 50-degree V with a single camshaft on each head. A central crankshaft sprocket drove a single timing chain, tensioned by an idler between the cylinders. Two carburetors, one on either side, fed the four cylinders (one front and one rear cylinder for each carb), with the exhaust exiting through four separate pipes. Two bevel-drive magnetos hung on the right side of the engine providing the sparks, while a front-mounted DC generator — sitting where, some speculated, a supercharger might fit — fed the battery.