AJS 500 V4 Review Motorcycle Trader New Zealand

25 Апр 2015 | Author: | Комментарии к записи AJS 500 V4 Review Motorcycle Trader New Zealand отключены

AJS 500 V4 Review

The product of this flight of fancy took a while to win a race. This was due to a desultory development path that was first interrupted by WW2, then disappointingly terminated by the postwar ban on forced induction. In due course however, it did lead to the creation of the bike which won the first-ever 500cc World Championship.

It was 1949 and the manufacturer was AMC — its AJS marque’s E90 Porcupine remains the only twin ever to have won the 500cc World title. The same company’s prewar GP contender, the supercharged 50-degree AJS V4 (using a Zoller compressor) was the first bike to lap a classic road race circuit at over 100 mph. The rider was Walter Rusk and it took place at the 1939 Ulster GP, just 15 days before the outbreak of WW2.

Fortunately the only surviving examples of both the pre-war four and post-war twin, are in the hands of someone who regularly puts them through their paces in public. Sammy Miller, their owner, is the fortunate man.

The story of the reconstruction of one of the crown jewels at the Sammy Miller Museum, the sole survivor of the two AJS 500 V4s ever made, is a typical Sammy Miller saga that has a personal link. Walter Rusk’s mother lived half a mile from our family’s home in Belfast, recalls Sammy, so he was a local hero even if I was too young to see him race the V4 — though I knew all about the bike and how fast it was.

After the war, when I rode my pushbike to the Clady circuit I saw and heard the Porcupines in action, which more than anything else is what switched me on to bikes and I dreamed of one day being able to ride one myself. The idea I’d ever be able to track down the two of them was a dream come true.

The key to doing so was the late Jock West, who via his job as AMC sales director not only obtained one of the title-winning E90 Porcupines, but also the supercharged V4 engine of the ex-Rusk bike he’d raced postwar. In the mid-’70s Miller acquired both the complete Porcupine and the V4 motor. The sohc V4 engine had seized a big-end in its last race, necessitating manufacture of a complete new crankshaft assembly, with the original pistons refreshened with rings from a C90 Honda parts bin.

Sammy and his team carefully rebuilt the engine, and coupled it, in the absence of the Burman original, to a postwar AJS 7R four-speed gearbox. New petrol and oil tanks were made to the correct shape and the newly restored V4 made its born-again debut in the 1980 TT Lap of Honour. It seized at Crosby owing to oil starvation, but not before Sammy had had time to discover the handling was distinctly lively.

Since its rebuild the supercharged AJS has spent quarter of a century as a rolling reminder of Mr. Miller’s resourcefulness and has publicised his superb museum via ongoing displays including, thanks to Sammy’s generosity, one in my honoured hands at the annual Goodwood Festival of Speed.

Lord March’s annual feast of automotive exotica proved an appropriate venue to sample this multi-cylinder mechanical jewel. Starting it is an acquired skill, especially in a crowded paddock. You must first prime the supercharger to get it to fire, so starting from cold requires a long-distance push, with the throttle held wide open, making sure you’ve flooded the low-set remote float bowl in front of your left foot.

Eventually the engine bubbles reluctantly, before suddenly catching with a high-pitched rumble from the four delicate megaphones. These replace the original less horny-looking straight pipes. Once firing on all four the supercharged engine does chime in very suddenly. You then need to blip the throttle furiously to keep the plugs clean, all the time to the muted whine of the Zoller compressor.

There’s no temperature gauge, so while in those push-start days with the difficulty of starting from cold you’d want to make sure the bike came to the line hot to trot, it would also be important to cool the fanless radiator so as not to risk what was evidently a perennial problem — blowing a head gasket through running it too long before the flag. Walter Rusk was a big man and he’d have needed to be to get the AJS off the line if the blower were less than ideally primed.

The four-cylinder bike as a whole appears less massive when you’re seated on it than when viewed from the side, and the engine is surprisingly compact in reality. It’s quite slim and thanks to the narrow-angle 50-degree format, has a rational 55-inch wheelbase resulting in a relatively close-coupled riding position.

Notch bottom gear on the AJS gearbox, with its slow but positive one-up right-foot shift action, and you’ll discover the dry clutch has a nice take-up. This lets you paddle up gently to the startline, all the time blipping the throttle so as not to let the plugs foul. The supercharged motor has a lusty pull from under 2000rpm to my appointed 6000 rpm rev-limit and peak power of 55 bhp.

Dry weight is a meaty 405 lb. The real surprise is how modern and sophisticated this prewar engine feels. It truly belies its age.

In spite of the lack of a counterbalancer there’s no undue vibration, and no vintage-style rattles and whirrs or extraneous mechanical noises. No wonder Honda copied the V4 engine format with a 180-degree crank more than 40 years later. In addition to the benefits of improved torque, and more compact build it also offers improved steering thanks to the engine’s compacted mass.

You do feel that in tighter turns the AJS swings more readily through the bend than bulkier in-line fours like the ’50s Gilera and MV Agusta 500s. It’s not as agile as a single, but no heavier-handling than a twin.

But that’s in slower turns. Elsewhere, the V4 AJS is a real handful, even, and especially, in a straight line. No wonder Sammy had suggested I give that big black steering damper knob a good twist just before the start. Taught always to do what I was told by my elders and betters, I duly cranked it up about three-quarters tight as I came to the line.

After a hint of waywardness rounding the second right-hander, which I put down to not having the tyres warmed up properly, the AJS started to buck and weave not altogether gracefully in a straight line. The bumpy surface threatened a genuine tank-slapper by asking the plunger rear end and girder forks to cope with high-speed road rash and the V4 required Rusk Style muscling into submission on the approach to the first left-hander.

It must have looked good to the champagne-quaffing dignitaries in the Sponsors’ Enclosure, but to me it underlined what a hero Walter Rusk must have been. To manhandle such a self-willed missile for three-and-a-half hours around seven laps of the TT Course, or for more than 70 miles in the lead of the Ulster GP is quite some achievement.

The V4 AJS was my first ride on a period supercharged 500 since I tested a BMW Kompressor, but comparisons are difficult as that was 17years ago. You must re-learn your riding technique. Basically, there’s no such thing as part-throttle. The throttle must either be wide open or switched right off, and I was vividly apprised of this exiting the slow left in front of Goodwood House.

I’d been trying to maintain some momentum with a whisker of throttle, after using the reasonably effective twin leading-shoe front brake and SLS rear companion to stop. The AJS didn’t appreciate this one bit, spluttering and coughing till I’d made the turn and twisted the throttle wide open again, clearing its throat and resuming normal service, until I had to slow again for the Flintwall flick. By now I’d learnt my lesson.

Squeezing the front brake lever hard, and stomping on the rear pedal, I closed the throttle tight shut, negotiated the turn, then wound it wide open again as soon as I’d hit the apex. Brake, point and squirt, that’s the secret to supercharged success. On — or off.

Though the 54 bhp eventually produced by the unblown post-war Porcupine was the same as the output of its 30 lb. heavier supercharged predecessor, I can’t help thinking after riding it that dumping the watercooled V4 engine of their prewar AJS GP racer in the wake of the postwar ban on supercharging, represented a truly missed opportunity by AMC management. This was arguably the first truly modern British motorcycle engine, which even shorn of a supercharger could have provided the basis for a road-bike that was years ahead of its time, especially in 650cc or even 750cc format.

Indeed a pity, but full marks to Sammy Miller for ensuring that such a significant step in BritBike history is preserved for us all to admire and enjoy seeing in action. Make sure you catch his next organ recital!

Photo credit: Kyoichi Nakamura

AJS 500 V4 — Specification

Engine: Supercharged watercooled sohc 50-degree V4 dry-sump four-stroke, with 180-degree crankshaft, two valves per cylinder, chain camshaft drive and chain-driven Zoller volumetric compressor

Dimensions: 50 x 63 mm

Capacity: 495 cc

Power torque: 55 bhp at 7,200 rpm

Compression ratio: 7.9:1

Carburation: 1 x 1 1/16 in./27 mm Amal TT with remote float chamber

AJS Model 20 500
AJS Model 20 500
AJS Model 20 500
AJS Model 20 500
AJS Model 20 500


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