AJS 500cc V-4: From myth to metal

Bike Profile

Dan Smith's AJS 500cc V4.

From our Old Bike Archives – Issue 75 – first published in 2018.

The remarkable story of one man’s dream to recreate what could have been one of the world’s most desirable motorcycles.

Story and photos Jim Scaysbrook

When AJS threw back the wraps on their star exhibit at the Earl’s Court Motor Cycle Show in November, 1935, the collective intake of breath almost sucked the carpets off the floor. Here, in solid metal, was perhaps the most mouth-watering, evocative and quite delicious powered two-wheeler ever offered to the public; a 50-degree vee with four cylinders, each with a single overhead camshaft driven by a central timing chain. It even carried a price tag – 89 guineas (when the average UK wage for a farm worker was about 100 Pounds per annum), suggesting that the order book was open for business.  The design was the work of Bert Collier, of the original Matchless family who acquired AJS in 1931. 

The only photograph released by AJS prior to the 1935 Earl’s Court Show.

Alas, the V-4 not only failed to proceed to production, the sole example disappeared immediately forever, although the basic concept lived on as a racer, which was initially air-cooled and later water-cooled. The racing version appeared in the 1936 Isle of Man TT, with London butcher Harold Daniell and long-serving AJS rider George Rowley forming the team. Neither finished and the V-4 project went silent for two years, reappearing with a supercharger. In 1939, the blown V-4, now with water-cooling, was entered for the prestigious North West 200 in Ireland, where Bob Foster overcame a bad start to hit the front before a head gasket failed. At the TT, Foster and Walter Rusk made numerous pit stops for fuel and water, but at least finished – in thirteenth and eleventh respectively. In August 1939, Rusk recorded the first-ever 100 mph lap at the Ulster Grand Prix, and impressed by leading the race until a broken front fork link sidelined him. 

Walter Rusk with the V-4 AJS at its last TT appearance in 1939.

The post-war ban on supercharging put paid to any further development, although the V-4 did manage a victory in June 1946 at Chimay in Belgium, ridden by Jock West. One week later at Albi in France, West was again at the head of the field when the engine seized, and a few months later came the ban on supercharging. The remnants of the sole remaining water-cooled V4 (still seized) initially went to the Beaulieu Museum before being acquired by Sammy Miller for his museum in the same district of southern England. The restored Miller example has appeared at several events, including the Isle of Man in 1984 and at the NZ Classic Festival at Pukekohe.

Sammy Miller’s 1939 AJS V4 at the 1980 Isle of Man TT.

Back to 1935

The motorcycle displayed at Earl’s Court was in essence four 125cc single cylinder top ends, with dimensions of 50mm x 63mm, giving 495cc, on a common crankcase. Both heads and barrels were in cast iron, with wide-angle valves and a hemispherical combustion chamber, giving a compression ratio of 7.9:1. Each cylinder head carried its own camshaft driven by a single chain running between each pair of cylinders. A half-time pinion drove the chain which ran up and over the front camshaft sprocket, down under a ‘Weller’ jockey pulley, up over the rear camshaft sprocket and back to the driving sprocket. The engine was in effect four overhead camshaft singles mounted on a common crankcase; the barrels, heads and cam boxes being separate castings. Hairpin valve springs, with duralumin rockers operated the valves via short tappets. Each cam box was secured to the cylinder head by four bolts.  Forked con-rods were used, with five ball and roller bearings supporting the crankshaft. Two Amal carburettors supplied the mixture, one on each side of the engine, mounted on induction pipes between the two cylinder banks. A bevel gear taken from the off-side of the crankshaft drove a short vertical shaft which in turn drove twin BTH magnetos, while the lower end of the bevel shaft drove the inlet and scavenging oil pumps. A Burman four-speed gearbox was fitted. The forks, brakes and wheels were identical to the catalogued AJS 500 single. At the front of the engine sat a dynamo, but AMC’s spruikers at the show ‘suggested’ that a supercharger could occupy this space without too much trouble. Its failure to reach production deprived the world of a sensational, ground-breaking motorcycle which would surely have become one of the most iconic designs of all time. Clearly, thought Dan Smith, this was a situation that needed to be rectified, albeit seventy years on.

Down in The Basement

I had come to Dan and Eileen’s home in Vancouver primarily to see a trio of motorcycles that Dan had constructed virtually from scratch, little realising there was much more to this amazing man – a devoted motorcyclist and a virtuoso of the workshop. That workshop is what Dan calls “The Basement”, located underneath the family home and a visual overload from the moment you set foot inside – an organised clutter of machinery, machine tools, patterns, castings, hand tools and gadgets, books and memorabilia. From within these somewhat cramped confines have (so far) come three motorcycles which Dan feels epitomise British motorcycle engineering from the golden era between the wars – originally from AJS, Velocette and Vincent. His business career as a skilled machinist certainly helped make the transition from dream to reality. “I realised very early on that if I learned how to be a machinist, I could make my own motorcycle parts.” 

Dan’s cramped by completely functional workshop is decidedly old-school, in that it contains no modern computer-controlled or assisted machinery. It’s decidedly slide-rule stuff; practical and precise. Everything starts with the drawing board and progresses from there. That’s all fine, except that reference consisted of a solitary, grainy photograph of the motorcycle itself, and an exploded drawing of the engine. Scaling up the internal components from the extant material was in itself a Herculean task as the engine drawing had been done in perspective, with up to six “diminishing points”, meaning accurate measurement was almost impossible. Even the sole-existing supercharged and water-cooled V-4 racer owned by Sammy Miller wasn’t much help, as the engine layout had been completely redesigned by Matt Wright in 1939 in a bid to make it competitive. 

Heart of the matter. The V-4 engine, built entirely by Dan.

Dan had some V-4 experience, having rescued a Matchless Silver Hawk from the scrap heap a few years previously, a task that involved recreating many of the internal components. But this was a comparative breeze compared to the AJS.  While he worked on the engine patterns, Dan set about accumulating cycle parts, which at least were something of a known quantity. “I looked at using a frame from a 1000cc V-twin AJS”, says Dan, “but it was too big and heavy. Instead, I managed to get one of the frames that Bert Denly used at Brooklands, with a 500cc single cylinder engine, and I made a full-sized wooden mock up of the V-4 engine. When this was mated to the Burman gearbox, it fitted into the frame – just. These frames are much the same as the standard AJS single frame of the time except for the rear end which has an extra latitudinal tube running to the rear axle mount.” 

Burman 4-speed gearbox. Rear magneto was found in Canada.

“I went to UK to look at Sammy Miller’s bike, but I soon realised that the water-cooled engine and the original air-cooled one were completely different. The water-cooled one was more compact, with shorter conrods, so the overall dimensions were all dissimilar. The cutaway drawing I had was not accurate either. It had been done so as to look right on paper, so the angles shown are not consistent. It was impossible to scale, so I had to resort to what I thought would be correct. I knew the bore size and the angle between the cylinders and after I worked out the length of the rods I was able to calculate the “deck heights” for the barrels on the crankcase. I spaced the magnetos at 60 degrees to make room for the bevel driving gears, and the pair of reduction gears to achieve the half-time drive.” 

Completing the patterns for the crankcase was a milestone, enabling the first castings to be made prior to commencing work on the crankshaft itself. “I used five main bearings instead of the original six. They (AJS) had two main bearings on the drive side but I figured with a power output of about 40 hp and running at 6,000 rpm that was unnecessary. I used two bearings in the centre, two outside the flywheels and one in the timing chest to control end-float. I didn’t see the sense in re-engineering every single component, so I used things like Vincent valves, re-machined, because I had plenty of them. Why make what you don’t have to?”

Handsome primary chain case was the last major item to be made.

Similarly, Dan used pistons from a DR100 Suzuki, and copied the Suzuki combustion chamber design and cam profiles. “I used vernier pin plates on the cams, like a Manx Norton,” he says, “with eccentric adjustment for the rockers.” Like the original, he used alloy rockers, and made small scavenge pumps for each of the cam boxes to return the oil. Suzuki also provided the extra-long cam chain – two chains from a DR400 that have been joined together. Hairpin valve springs originally from a 250cc NSU Max fitted nicely. Twin BTH magnetos supply the spark; one found locally in Canada and the other coming from Tasmania after Dan discovered it on eBay. He made the gear cutters for the magneto bevel gears, as well as the gears themselves. A BSA 10 was the donor for the oil pump. Unlike the original AJS design which used a single float chamber for each of the Amal carburettors, Dan used twin float bowls for each. The original AJS used cast iron heads and barrels, but Dan opted for cast alloy components in the name of efficiency and expedition. 

Engine and rolling chassis were united in early 2006, after which Dan was able to design the remaining major component, the primary chain case. Again, it was a case of careful measurement and drawing before producing a pattern and casting. With the machine basically complete, it was then time to pull it all apart for plating and painting. Now with the wind in his sails, Dan had the bike back together later in the year and after considerable hard graft to arrive at ignition timing, clearances and carburettor settings, it was time to give it a kick. Whether the 1935 Show bike was ever started, or in fact whether it had the engine internals to allow it to run, Dan’s certainly does. It wasn’t able to be started during my visit, but Dan says the exhaust note is unlike what you’d expect from a V-4, and more like a Laverda triple. 

Left: Fuel tank came from a ‘thirties AJS 600 single. Right: Apart from the mufflers, the rear gives little away.

The stunning machine has since clocked up over 10,000 miles, and has even been dropped, albeit at slow speeds, by a visitor. Dan himself has given the V-4 a good workout on occasions. “I’ve had it to 95 (mph). I replicated the handling too. I got this frame off a 600, and all that is a second member going back to the back wheel that stiffens up the back end a bit, but it’s the front end that’s flimsy. It goes fine, but I had an Australian chap here who rode it and he must have loosened off the steering damper, and then the following week a chap from NZ, Frank Platt was visiting and we went out, (I was on my Ariel Square Four), and I said ‘Go ahead, roll it on’, but he shut off the throttle real quick and it went and spat him right off. He bailed off and hit the road running; he was a guy my age and he never really went down but the bike hit hard. We were scheduled to go to Colorado to an invitation car and bikes show, so a couple of things had to be plated and doctored up but it wasn’t too bad, it could have been much worse.” 

A committed couple

When Dan Smith retired in 1998, he and his wife Eileen decided to take a little trip. He’d worked hard and built a successful engineering business, and along the way had collected some desirable motorcycles, notably Vincents. And so his Rapide, suitably but subtly modified for the task with a big fuel tank and luggage carrying equipment, was readied for a journey that would take the couple from their modest home in Vancouver, B.C. where they had lived (and still do) for 52 years, to as far south as roads would take them – to Tierra del Fuego on the tip of South America. 

Dan and Eileen in the garage of their Vancouver home, with the much-travelled Rapide. Note the HRD’s front mudflap, a vital piece of equipment says Dan.

“It’s a nice bike to ride. The mud flap on the front fender is a great thing for keeping foreign objects off the back tyre. I went to South America and back and never had anything puncture my tyre in 30,000 miles. Eileen and I were nine months on the road, 15 thousand miles down to Tierra Del Fuego on my Rapide. I made the big tank and put the rack on it and set it up so it was OK for touring. That was ‘98 shortly after I retired. We couldn’t ride all the way back – it was the year of the big El Nino and the hurricanes were coming through Central America and the northern part of South America and the roads got washed out. We got to within 7 degrees of the equator coming home and we had to go back into Lima and fly it (the Rapide) from there. The trip was over but when we got back we went up to the midnight sun in Alaska. We didn’t camp, we stayed in a hotel every night. I never had anything physically go wrong with it. If you’re on your new BMW and something breaks you gotta wait until the parts come out. I had a wet ignition system, and we went through three hurricanes. I broke the rear frame from bumping it back onto the rear stand; that was in Mexico so I had that welded up and it’s still the same, but nothing mechanically went wrong all the way down and back. It’s put together more or less like a stock Shadow with inch and an eighth carbs, has a 4 speed whereas my Shadow has a 5 speed. 

The Shadow is short rodded – the rods are 5/8 inch shorter – the pushrods just clear each side, you take a fin off the top and one off the bottom of the muff. It has a titanium oil tank and aluminium fastenings, on 10.6:1 it goes like stink. That was made from nothing, I acquired a set of cases and I got carried away making a hot rod out of it. It will do 140 if you’re drunk enough. Jetting the carbs I was doing 125 and still coming on, shifting into top gear. It has a Surtees 5 speed gearbox, his first one. I was drawing up a five-speed when I got wind that John Surtees was doing it so I got on the phone and said I’d take one. It was 3 years later when I got it and it was a close ratio box – no good for the street – so I had to change low and second which was easier than making a whole gearbox.”

Dan Smith – man and machine.

But wait, there’s more

From reading this far you will have gathered that Dan Smith has legendary status in the Canadian motorcycling scene. His enthusiasm is infectious, his engineering skills truly inspirational, and the products of his little workshop almost beyond belief. In future OBA issues you will read of two more of Dan’s creations – his Velocette Roarer and the first of his Vincent HRD Series A replicas (the second was still under construction at the time of my visit). However he admits that the years of hard work are taking their toll. “I still spend eight hours a day in the basement,” he says. “I still enjoy it but it’s not getting any easier. I’ll be eighty soon. That’s why I have decided to sell the V-4 AJS and the Roarer. I am not in any hurry because whoever buys them will need to have deep pockets. I’ll keep the Series A because I ride that one often.” Whether it’s a museum or an individual who ends up with the bikes, these machines represent an incredible achievement in engineering terms and in sheer determination. In the case of the AJS, it also means a prototype that scarcely saw the light of day now exists in a form where it can be marvelled at by current generations, more than seventy years after it was conceived. 

OBA Issue 75
This article first appeared in Old Bike Australasia Issue 75. You can still purchase this back issue by clicking the cover for more info.