AJS Stormer 250cc. 1969.

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26. AJS Stormer 250cc / 1969

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Malcolm Davis / AJS Stormer 250cc / 1969

When you unbolt the stable door on the new 250cc AJS Scrambler, 27 horses come galloping out at a terrific pace!

There is no hesitation – they kick you straight in the pants and you spend the next few seconds trying to tame the unleashed power and bring the bounding bucking machine under control.

Drop into second gear and open the throttle and still the front rears upwards almost as though the machine wants to unsaddle you.

There’s no doubt that AJS have produced a thoroughbred and in just two short years of development have swept the scrambles board in Britain clean, to take the British 250 Motocross Championship by a clear 13-point margin.

Works rider Malcolm Davis has had his fill of disappointment over the past two seasons but by perseverance, any problems with the early frame, suspension, engine, carburation and electrics have been overcome.

High-speed film cameras and slow-motion film were used to study suspension of every type of scrambles machine in action and from 18 months of tough, racing development, AJS now have the champion 250cc two-stroke scrambler.

Identical models to the works machines are now in production and it was one of these machines that we were invited to test at the new AJS works near Andover.

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Fluff Brown the heart of the Team / Thruxton / 1969

Not being a works rider or expert scrambler, it is very difficult for me to cast an expert opinion as to how the new AJS Y4 compares with other makes in the class.

But after spending some time lapping the small test circuit, I can at least give you my impressions regarding the performance, handling and power output that this machine provides.

As I’ve already mentioned, the power from this seemingly conventional two-stroke is terrific. At a mere 6,400 rpm it produces 27 bhp and the actual power band is spread so wide that even with the engine running almost down to stalling point, it will still pick up and accelerate quickly to its maximum.

This means, of course, that whether you’re in sticky mud or sand, the tractability of the motor will pull you through.

Also, the weight factor of the machine is very important as with a total of 220 lb. for 27 bhp, the Y4 has the very impressive figure of 135 bhp-per-ton equal to the very best.

The motor has standard piston controlled two-stroke porting but, obviously, the actual positioning and size of the ports play a major role in the power extracted from the engine.


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The compression ratio is a tough 12.3: 1 and the bore and stroke are square at 68mm. Carburation, is affected by a modified Amal Concentric 932 model carburetor.

Starting the bike was no problem, when warm the second kick brought results and when cold, it was simply a matter of flooding the carburetor slightly, and when the motor fired, keeping it revving until it was warm and clean on carburation.

Response to the throttle was instant on any occasion and there appeared to be no signs of the motor going “ off the mega “ – a common complaint with tuned motors when the revs drop. A great deal of work has gone into the design of the upswept expansion exhaust system to obtain the “correct” scrambles motor characteristics.

An all-metal diaphragm-type clutch is used to transmit the power of this poky little motor to the four-speed gearbox. It is very light to use and very robust. In fact, the gearbox is a delight and using this clutch, only the lightest of pressures is required, to swap cogs in the gearbox.

The company virtually makes everything; the engine/gearbox; the exhaust system; the front forks and the frame, on this new AJS scrambler.

Only proprietary items such as the carburetor, tyres and wheel rims are made elsewhere.

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Considerable thought has gone into every detail on the Y4. For example, the brakes, which have to work under grim conditions from wet muddy water to dry dusty circuits, have a special sealing ring to keep all damp and dirt out.

It is the careful thought, which has gone into these seamingly minor items that has produced the AJS Stormers reliability.

The same thorough approach to design in order to keep water out of the works has also been made, with the electrics and carburetor intake.

Reliability is the keyword and it has been proved that the AJS has, after a short 18 months of development, made the grade by winning the British Motocross Championship.

What’s it like riding the machine? Well after completing three cautious laps of the test circuit, I begin to get used to the bumping, bouncing and shaking, and then I really started to enjoy myself.

The light weight of the bike made it perfectly controllable – most of the time – and if one did get into a spot of trouble it was simply a matter of opening the throttle a bit more and showing the bike who was really in charge.

Only once did it pitch me off – just to prove that you couldn’t win all the time. However this was no fault of the bike, just my nervous approach to a bend during which I happened to touch the front brake too hard. Golden rule number one broken – don’t touch front brake on slippery surface on bend.

The handling of the machine was perhaps the most surprising feature apart from the sheer power, it was perfect.


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Malcolm Davis / AJS Stormer 250cc Y4 / 1969

The confidence one achieved while belting along over bumpy, slippery surfaces was really something and could all be put down to the unique frame design.

A really robust spine tube is the heart and strength of the unit and the remainder is made up of lightweight, triangular sections for rigidity.

The result is a complete motorcycle with minimum of whip over the most tortuous terrain. The AJS designed and made front forks coupled with matched Girling rear units complete the frame parts and with a front fork travel of seven inches and rear travel of just over three inches, the mount keeps the wheels firmly planted on bumpy surfaces.

That is of course when the bike isn’t leaping the brows of hills as sure footed as a spring lamb. Future plans for the AJS marque are constant development; to improve this already fine machine and both Malcolm Davis and Andy Roberton will be taking on the World Champions next year.

As works team riders they are confident that they will be in with a chance against the all-powerful Continentals.

When the AJS name died at Woolwich, who could have believed that it would be reborn so successfully.

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Peter Inchley / California / 1969

It’s obviously a winner put in the right hands!

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