Speedway Jap
speedway JAP
TONY HOGG
ALTHOUGH ENGLAND is commonly thought of as the home of motorcycle road racing, a very big spectator attraction is the night speedway racing which thrills the crowds at 1/4 and 1/5 mile tracks in many of the major cities. Due to its very specialized nature, this racing has produced a machine that bears little resemblance to the motorcycle as we know it although, in the hands of a skilled rider, it will circle a quarter mile track in an unbelievably spectacular and rapid manner. The machine is usually referred to as the "Speedway JAP" because it is always powered by a J.A.P. engine, although a variety of frames are used.
Started some thirty years ago, speedway racing has never been n amateur sport, but has been conducted in much the same way as the American baseball clubs, hav ing professional riders signed up to teams under contract, and the teams riding against each other in a series of heat races with points being awarded for position. There has always been a strong interna tional flavor to the sport, with contingents from Australia, New Zealand, South Africa and Sweden, and, before the last war, several Americans, such as the Milne brothers, Jack and Cordy, and the late, hard-riding Wilbur Lamoreaux, were al ways popular with the crowds.
Unlike other forms of European racing, a definite circus atmosphere has always prevailed at the speedways and, as in the circus, the star performers are paid well. In fact, many of the top riders over the last three decades have made considerable fortunes, which is not surprising to anyone who has seen Wembley Stadium in Lon don filled to its capacity of 90,000. Al though rewarding, it is also an extremely hazardous and demanding profession, which calls for great precision and skill, and also a lot of courage.
England has always been the center of the sport, and consequently where the money lies, but a number of tracks used to operate in California in the thirties, and a revival was attempted in the im mediate post-war period, although without much success. However, Larry Pricer of Sacramento, California, feels that the sport is still a good spectator attraction, and is planning to promote a series of events in that area with a group of some twenty or thirty riders and machines which he has gathered together. Among the enthusiasts in Sacramento is Jack Gormley, who owns an almost perfect example of the Speed way JAP he has ridden in several events.
Gormley's machine was probably con structed in 1949, and can therefore be described as "up to the minute" because
few changes have been made to the de sign in the last two decades. The basis of the machine is the JAP engine, which appears at first sight to be an aged and rather crude piece of machinery. How ever, it is remarkably effective and puts out some 45 bhp from its 500cc, and has a torque curve which is exactly tailored to the tracks on which it performs.
Both the head and barrel are iron, and the finning is reduced to an absolute min imum on each, which is most unusual in a racing engine. However, it must be remembered that the unit was designed to run on alcohol in very short events, and of course the cooling properties of alcohol are well known. In the early fifties, some of these engines were adapted for use in small race cars, which did produce a cool ing problem; however, this was solved by the use of a special alloy barrel, although the normal head was retained.
The valve operation is by push rods, and the bore and stroke are 80 x 99 mm, making it a very long stroke engine by today's standards. However, when con sidering the length of the stroke, it must be remembered that standard compres sion ratio is 15 to 1, and it is easier to obtain an effective combustion chamber shape with this kind of ratio if the stroke is long. At the same time, when this long stroke is combined with the comparatively conservative valve timing of the JAP, excellent low speed torque results, which is an impressive feature of the engine.
Actually, the machine will accelerate like a shot from a gun from 1,000 rpm to its peak at 6,000 rpm with a smooth surge of power, and without any of the fuss normally associated with a racing engine. This characteristic is essential on the track because the rather sensational technique used by the riders depends to a great extent on an extremely accurate and responsive throttle.
The carburetor is a twin-float, track Amal, which is designed specifically to ensure an adequate flow of fuel under all the conditions peculiar to speedway racing. Ignition is by a BTH magneto which, once again, is specifically designed for the job, and another unusual feature of the engine is the lubrication system by a Pilgrim pump which works on the constant loss principle. This pump is driven from the timing side of the engine, and is supplied by gravity from a one-pint oil tank under the seat. There is no return to the tank at all, and the oil drips down into a chamber on top of the pump which has a window in it, and the oil flow can be adjusted by looking into the window and timing the number of drops per minute. Two adjusting screws are provided, which take care of the flow to the bottom end and the flow to the rockers, and any surplus oil is discharged onto the track through a pressure relief valve in the crankcase. In this way, the engine is supplied constantly with fresh oil, although it works under extremely dirty conditions. Castor oil is its normal diet, and Jack Gormley uses a medicinal quality which he obtains from a friendly drug store.
If the engine is peculiar, the cycle parts are more so. Frames for these machines are constructed by several different companies such as Victor Martin, Rudge or Excelsior, but the basic design is much the same in each case and, as can be seen from the illustrations, nuts and bolts are used in preference to welding at several points. An interesting feature of the design is that a degree of flexibility is built into the frame, which necessitates the engine sprocket being mounted on a spline with a movement of about % of an inch so that the primary chain is self-aligning.
When assessing the performance of a motorcycle for CYCLE WORLD, it is always a problem to know what to say about brakes. However, in the case of the Speedway JAP, this problem doesn’t arise, because the machine just doesn’t come with brakes, and has to be brought to a standstill by the time-honored method of dragging your feet along the ground. For those who might consider down-shifting as an alternative, it must be pointed out that the machine doesn’t come with a gearbox either, and this unit is replaced by a simple countershaft with a clutch on the end of it, and it is necessary to withdraw the clutch to wheel the bike around.
Among other items that are considered unnecessary are all instruments and all controls other than a clutch and a throttle. A minimal rear fender is fitted, which is designed to prevent the rear wheel from throwing the surface of the track into the engine, and the footrest on the left side is eliminated. The frame is rigid with no rear suspension, and the total movement of the front forks is in the region of IV2 inches. The tires are distinctly agricultural in appearance, and Jack Gormley’s machine is equipped with a pair of Avon Special Speedways which are 23/s x 22 in front and 2.75 x 22 in the rear.
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cont.
In attempting to describe the ride, it is necessary to take into account the fact that the machine is worn like a glove rather than ridden in the accepted manner. The seat is unsprung although padded, and the single footrest is far back and is used in conjunction with a padded knee rest which holds the right leg firmly to the machine. The handlebars are wide and curved and the machine is ridden in an upright position, which is no particular disadvantage because the maximum speed on most tracks rarely exceeds 70 mph.
At most of the English tracks, the starting area is concrete and, to ensure that nobody jumps the gun, a gate is employed which is similar to the type used in horse racing. The track is composed of cinders which provides a loose but very consistent surface, although a surprising amount of maintenance is required to keep it in good condition.
All races are run over four laps from a standing start and are contested by four riders, two from each of the opposing teams so that a considerable amount of track craft is involved. The aim is obviously to get both riders from a team in front where they can ride very closely together with one outside the other in the turns so that the opposition can’t get a wheel in anywhere. However, this is not as easy as it sounds because it has to be done at maximum speed, and many a tangle has resulted. An additional advantage of getting in front at the start is that the machines throw a jet of cinders from the rear wheel, which is most disconcerting to the following riders.
As far as the technique is concerned, a fast smooth start is essential which requires considerable practice if excessive wheel spin is to be avoided, and if the front wheel is to kept on the ground. Due to the nature of the track, the machine is never quite free of wheel spin, although the rear wheel will bite deeply when the bike is accelerating on the straights, and the speed through the turns is quite alarming because this is where the Speedway JAP comes into its own.
The bike is geared to reach its peak of 6,000 rpm at the shut-off point and, as soon as it has slowed and is under control, the rider cracks the throttle and, by throttle control, holds it in a long slide in which it’s all crossed up. As soon as the next straight appears, he can open it up fully, although this is always a critical point, because an excess of zeal coming out of the turns can easily put the whole lot through the fence.
By its nature, the attraction at speedway racing has always been the men rather than the machines, but this does not mean that the machines are uninteresting. Actually, the Speedway JAP is one of the most functional and vicious motorcycles ever produced, and its performance is quite startling. Some people may feel that it is nothing more than the tool of a trade, which is to some extent true, however it is still a most interesting and effective tool of a hazardous and exciting trade.
