In a funny twist of lingering history, the FIM book of Motorcycle Land Speed Records notes that on 6th November, 1930, Joseph S. Wright took his Temple-O.E.C. (Osborne Engineering Company) with supercharged JAP 994cc engine to 150.7 mph down the rod-straight concrete pavé at Cork, Ireland. The 1930 record was a significant advance on the Ernst Henne/BMW record of 137.58mph, achieved only weeks prior at Ingolstadt, Germany, on a supercharged 750cc ohv machine. But in this case, the history books are all wrong.
150 MILES AN HOUR ON A MOTORCYCLE!
(Click on the image above to see the film from the Record attempt)
The O.E.C. was an unusual motorcycle, using 'duplex' steering; an OEC trademark, although not all of their bikes used this system. The advantages of this arcane steering system on these early motorcycles was great stability at speed, plus the possibility of front wheel suspension which didn't alter the steering geometry when compressed by bumps, giving totally 'neutral' steering under all conditions. In practical use, the OEC chassis was reported to be very stable indeed, although resistant to steering input! So, while potholes and broken surfaces brought no front wheel deflection, neither did a hard push on the handlebars...perfect for a speed record chassis actually.
A pair of machines was present at Cork that day; the OEC which had been prepared by veteran speed tuner Claude Temple, and a 'reserve' machine in case it all went pear-shaped. The second-string machine was a supercharged Zenith-JAP, of similar engine configuration to the OEC, but in a mid-1920s Zenith '8/45' racing chassis. Zenith at that date was technically out of business, so no valuable publicity could be gained for the factory from a record run, nor bonuses paid, nor salaries for any helpful staff who built/maintained the machine. While Zenith would be rescued from the trashbin of the Depression in a few months, and carry on making motorcycles until 1948 in fact, the reorganized company, with its star-making General Manager Freddie Barnes, never sponsored another racer at Brooklands or built more of their illustrious special 'one off' singles and v-twins, which did so well at speed events around the world - from England to Argentina!
Supercharging a v-twin motorcycle is a difficult business, as the compressor blows fuel/air mix at a constant rate into a shared inlet manifold for both cylinders, but as the cylinders aren't evenly spaced physically (as they are on a BMW, for instance), one cylinder inevitably gets a much bigger 'puff' of built-up pressure. Figuring out how to accommodate a different charge for each cylinder led to all sorts of compromises, from restricting the inlet port of one cylinder, to the use of different camshafts/compression ratios/valve sizes for each cylinder, in an effort to keep one cylinder from doing all the 'work' and overheating. It was an imperfect science, as supercharging was still relatively new to motorcycles, and only a handful of blown motorcycles were truly 'sorted out' for racing or record-breaking before WW2. Typically, these had flat-twin or four-cylinder engines, with even intake pulses! (Although, of course Moto Guzzi, typical of their genius at the time, had a lovely 250cc ohc blown single-cylinder which worked a treat).
With the OEC out of action, and FIM timekeepers being paid by the day, as well as the complicated arrangements with the city of Cork to close their road (and presumably police the area), a World Speed Record was an expensive proposition, and the luxury of a 'second machine' (above) was in fact very practical...although this may be the only instance in which the second machine was of a completely different make. Imagine Ernst Henne bringing a supercharged DKW as a backup for his BMW; simply unthinkable!
But, such was the English motorcycle industry at the time; several very small factories (Brough Superior, Zenith) competed on friendly terms for national prestige the in record books, while the largest makes (BSA, Triumph, Ariel), nearly ignored top-tier speed competitions such as the Grands Prix and Land Speed Records.
In the event, Wright did indeed set a new Motorcycle Land Speed Record with his trusty Zenith (above, setting the record, quite clearly on a different machine than the OEC below) at 150.7mph, although the press photographs and film crews of the time were solely focused on the magnificent but ill-fated OEC, as Zenith was out of business and OEC paying the bills. Scandalously, all present played along with the misdirection that the OEC had been the machine burning up the timing strips, and the Zenith was quickly hidden away from history, a situation which still exists in the FIM record books!
The record-breaking Joe Wright Zenith was a rumor for decades, becoming a documented story only in the 1980s via the classic motorcycling rags, the whereabouts or existence of the Actual machine known only to very few. I've had the great pleasure of making the Zenith's acquaintance, it does still exist, and is currently undergoing restoration, to be revealed when the time is ripe.