Offered from the estate of the late Clifford Jones, the ex-Steve Machin, Roger Marshall
1973 SCITSU-Yamaha 475cc Racing Motorcycle
Engine no. 521-001240
Although the most famous three-cylinder Yamaha racer is that built by the Dutch importer and used by Takazumi Katayama to win the World 350cc Championship in 1977, it was not the first such machine to grace the racetrack. American tuner Doug Schwerma is credited with being the first to add a third cylinder to a Yamaha twin (a 350cc TR2) to make a 525cc triple, while in the UK one of the first to try the idea was Sheffield-based engineer Tony Dawson, creator of the Astralite wheel, who built the original SCITSU triple in 1973. (For those not already aware, SCITSU stands for 'Selfish Conduct Injures True Sportsmanship and Unity'). Among others who went down the same route were Ted Broad, Dennis Trollope and Arnold Fletcher of Len Manchester Motorcycles.
Depending on which Yamaha engine was used - 250cc TD or 350cc TR - and the size of the additional cylinder, a range of different capacities could be arrived at. Thus combining a 350 twin with a 250 cylinder resulted in a 475cc unit, ideal for the 500cc class, while if the additional cylinder was from a 350, the capacity would be 525cc making the machine eligible for the 750cc or unlimited classes. It should be remembered that this, before the arrival of the Yamaha TZ750 and Suzuki RG500, made it possible for privateers to buy purpose-built racing machinery for these two classes.
Tony Dawson's first SCITSU triple, based on a Yamaha TR3 engine and displacing 525cc, debuted in 1973. The machine offered here, it had been produced at the behest of Lincolnshire-born racer and three-time British 250cc Champion Steve Machin, who had heard of Ted Broad's plans for a similar 'special'. The Machin/Dawson association had begun when Tony supplied Steve with a gear set for his Yamaha AS3 racer, a successful upgrade that was later sold through the garage run by Steve and his business partner, Dave Saunders, at West Barkwith in Lincolnshire.
Tony Dawson has recalled that the original SCITSU three-engine started out using YDS7 cranks that have six splines, making the construction of a 120-degree crankshaft relatively easy. However, the cranks kept breaking so he decided to make his own. Tony worked at the British Iron & Steel Research Association (BISRA) so could get forgings and other parts manufactured, and he used BISRA facilities to machine the crankcases. Having had the forgings made, Tony then decided on a different approach and opted to make a '500' (actually 475cc) using Yamaha TZ cranks. Unfortunately, the latter have a less than ideal 11 splines. Using a 125cc TD3 additional cylinder to achieve the desired capacity, Tony phased the crankshaft throws at intervals of four, four and three splines (130, 130, and 100 degrees approximately) with the TD3 cylinder on the 'short' phase. Surprisingly, in this configuration the engine ran smoother than it had using the 120-degree crankshaft!
In its first, 525cc configuration, the SCITSU was ridden by Roger Marshall on its track debut at the 'Cadwell Conqueror' event in the summer of 1973, having been tested by Roger and Mick Grant the previous Thursday. Roger made a good start in the second 1,000cc heat, only for the SCITSU be forced out with a broken gear selector, a fault that had not manifested itself during 70 faultless laps of testing.
With Steve Machin aboard, the Maxton-framed SCITSU scored its first victory at the Snetterton Combine meeting, defeating the formidable combination of Barry Ditchburn and Ted Broad's 521cc Yamaha-based triple in the unlimited race. The SCITSU proved itself to be significantly faster than the Broad bike, and Steve set the day's fastest lap at 97.56mph. Sadly, 1973 would turn out to be Steve Machin's final full season of racing; an immensely likeable and highly respected competitor, he died following an accident at Cadwell Park in July 1974.
The SCITSU was subsequently owned by Brian Spooner, followed by Steve Carthy. However, little else of its post-1974 history is known and further research would surely prove rewarding for the fortunate new owner of this historic machine. Apart from Steve Machin, everyone else involved in the original SCITSU triple project is still alive and Bonhams would like to thank Tony Dawson, Dave Saunders and Roger Marshall for their assistance.
Without the ambition of Steve Machin and the engineering skill of Tony Dawson, this unique SCITSU would never have existed. It belongs to a 'golden era' of motorcycle racing in Britain, when the world's top Grand Prix stars would regularly compete on mainland circuits against this country's best home-based riders.
It is only fitting that Tony Dawson should have the last word: 'We would all like to have something to remind us of a unique period in our racing lives and so hope we could one day point at something that is representative of what we did as a glorious team under the stewardship of Steve, surely the nicest guy ever to throw a leg over a race bike. What he did for others still has influence today and for me most especially so.'
- This lot is withdrawn from the sale. It will be re-offered on the 20th October at Classic Motorcycle Mechanics Show, Stafford.