12. Cotton Starmaker Range
When it comes to versatility, the current crop of high-performance 250cc two-stroke singles really hits the jackpot. For sportsman in nearly all fields this is a great time. It means that a basic engine design can be served up to suit the road racer, the scrambler, the trials addict and the rider who merely wants a peppy roadster.
You can in short, have poke, punch, plonk or purr to order.
Cotton’s are the first to list machines of all four types with a common engine – the Villiers Starmaker.
Since performance requirements vary widely in the four fields, how is the switch made?
Basically by ringing the changes on those aspects of design that exert a crucial influence on power characteristics – the resonant exhaust system, cylinder porting, primary and secondary compression ratios, and carburation. When the Starmaker made its debut two years ago it was purely a scrambles engine – with an out-of-phase twin-carburetor induction layout that later gave way to a conventional single port with an Amal Monobloc carburetor.
DMW Hornet Starmaker 250cc 1964 / Bill Smith, in the saddle, Peter Inchley left.
Success of the subsequent racing version with an Amal GP carb and independently supported contact-breaker cam, is shown by Derek Minter’s 250cc ACU Road Racing Star win this year on his Cotton Telstar and Bill Smith’s Isle of Man Southern 100 victory on his DMW Hornet.
Cotton Starmaker Trials / Colin Dommett / 1964
Modifications of the engine, for Cotton’s Conquest, have yet to be finalised for the 1964 Earls Court Show, but it was shown with a Monobloc carburetor and air filter, but the trials version is well in its stride. This has a Villiers S25 carb, wide spaced gear ratios and greatly reduced compression ratios. The drop in primary compression is achieved by using part, not full, flywheel discs. An ordinary part spherical combustion roof, instead of the unusual toroidal shape, cuts the secondary ratio from 12.5 to, 8 to 1.
To appreciate the pace of competition in the racing field you have only to think of Villiers building a complete machine for themselves, the Starmaker Special. This is virtually a Bultaco, powered by a six-speed Villiers Starmaker racing engine. The scheme is for Peter Inchley, who is employed by Villiers on Starmaker development, to race it and shorten the communication time between track and test house as much as possible, it only awaits sufficient orders to go into production.