| The Villiers Starmaker
engine and transmission unit was introduced early in 1963. The intent was to
make available to motorcycle manufacturers an engine and transmission
producing the performance level needed to compete in the motorcycle sport
known at the time as Scrambling, at International Level. The engine had
capacity of 250cc having a specific power output of 100 bhp per litre.
The engine and transmission
unit that carried the name Starmaker represented a departure
from the traditional method of product identification used by
the company. For many years the company had resisted using names
for company products since the early days, when the bicycle
known as the "Sunbeam Cub" was produced by the company.
When Villiers began to
manufacture internal combustion engines in 1912 a code system of
a combination of numbers and letters had begun to be used to
describe the type of engine and engine capacity, and this had
become the traditional method of product identification. In 1963 this new engine and
transmission initially was intended for use in the type of
motorcycle racing known as Scrambling, although other
applications were being considered.
Very soon after the Starmaker
was made available, the controlling body of the sport decided
that the name Scrambling did not translate easily into other
languages. To overcome this difficulty and to adopt a name that
reflected the increasing interest in the specialized motorcycle
racing throughout the world, soon after the Starmaker was
introduced, the more modern and more universal name Moto-Cross
was adopted. The unit replaced similar
engine power units made by the company, namely the 34A and 37A
which in turn had evolved from the venerable 9E.
The units the Starmaker
replaced had reached the limit of power development and
performance, and it was considered that only a redesigned
replacement would be able to meet the forecasts of the needs of
the market in the future of moto-cross racing that rapidly was
becoming an international motorcycling sport. The responsibility for
the design of the Starmaker was given to two designers employed by the
company; Bernard Hooper, a two stroke engine design specialist and John
Favill (the author) who had developed a design specialization in gears and
transmissions.
Motorcycle companies
that purchased the Starmaker included DMW (a Sedgley company), Greeves,
Cotton, James, and DOT.
After the introduction
of the engine and transmission assembly to the motorcycling world, one of
the developments soon after the introduction to the Moto-Cross application,
was the use for road racing. The engine and transmission unit enabled race
competitive road racing motorcycles to be made available at a relatively low
cost. The 4 speed gearbox was provided with close ratios but in addition, a
specially designed six speed gearbox was made available. This road racing
version of the unit was provided with a tachometer drive, plus an attachment
to the timing side of the crankshaft that carried the ignition points in a
separate bearing support that provided for better spark control for the
ignition system at the higher engine speeds used for road racing. The
developed power output was increased to 32 BHP at 7500 rpm. (128 BHP per
litre). Motorcycles powered by
the road racing version of the engine and transmission did very well on the
racing circuits in the UK both for Moto-Cross and Road Racing, but the most
outstanding year occurred in 1966. A Villiers built road racing motorcycle
was ridden by Peter Inchley, (an experienced rider employed by the company
for motorcycle development) to 3rd place in the Isle Of Man TT race for
250cc machines. This was the first time for 16 years that a British machine
had finished in the first three and the first time a single cylinder machine
had lapped the TT course at an average speed of over 90 mph. ( 91.43 mph)
The only machines to beat the Starmaker were special multi-cylinder works
machines made by Honda.
The third application for the Starmaker engine was for what was
known as Trials, represented by such competitions as the famous
Scottish Six Days international event. Torque output of the
engine was critical for this application coupled with reliable
and instant engine response. A wide ratio gearbox was made
available for this application, with the maximum power output of
the engine set at 14 bhp at 5500 rpm.
The other application,
although a relatively small quantity of engine were used, was for four wheel
Formula IV car racing where the road racing version of the engine was used.
Technical Specification of the
Starmaker engine and transmission
All versions of the Starmaker
engine had a cast-in austenitic spun cast iron cylinder liner,
the ports of which were machined and used to locate the shell
moulded sand-cores of the cylinder, ensuring accuracy of casting
at all times and consistency of engine performance.
On each model the piston had
narrow rings and a large diameter piston pin. The crankshaft
assembly had a thin section forged-steel connecting-rod running
on a caged needle-roller big-end bearing. The road-racing and
moto-cross engines had full circle cranks to help provide the
high crankcase pressure required for these engines. The
crankshaft was supported on two steel roller bearings, plus a
needle-roller bearing on the drive side. At the time the caged
needle roller bearing used in the big-end represented the limit
of the technical know-how on this type of caged bearing
application. The engine performance
levels, particularly in the road racing application, provided valuable
research information in the development of technical design know-how for
big-end cage design that has now become common practice.
The clutch was the first
application of the use of a diaphragm spring in a clutch to be used on a
motorcycle. Diaphragm spring clutches have now become universally used on
both motorcycles and cars. The clutch had two sintered bronze friction
plates with one steel intermediate plate, pressure being applied by a
diaphragm spring. Although the clutch had a very high spring pressure the
natural mechanical advantage allowed by the diaphragm spring plus the scroll
type release mechanism ensured light finger pressure at the handlebar lever.
The extremely robust
gearbox had shafts and gears of nickel chrome steel
(B.S. En36B
Specification). All splines were of involute form and the shafts and
rotating gears were carried on needle roller bearings.
The magneto was of the
energy-transfer type with energizing coils carried in the stator plate, and
transferring current to a separate encapsulated coil, which could be mounted
on the motorcycle frame. Trials engines had a 6 volt direct current lighting
system.
Drawings of recommended
exhaust systems for each engine application were available, together with
information on their effect on power and torque curves. Road racing units
were provided with a tachometer mounting and an independent bearing support
and self contained drive system that carried the points for the ignition
system.
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