Bianchi 250 1957-58
In a comparatively few years the Italian
Bianchi concern has thrust its name to the forefront of road-racing. This
post-war interest on the factory's part stems from 1956 when they built up a 203
c.c. version of their push-rod roadster "i75"j the "Tonale", and developed it as
a road-racer. This machine won several important 250 c.c. events in Italy, and
for 1957 it "grew" a chain-driven o.h.c. and then some more c.c.s and a
gear-driven camshaft. This model proved very good but, as things happen, factory
interest waned; it recurred in i960 but this model was superseded by a new twin.
Nonetheless, the single appeared fleetingly in the Isle of Man in June i960 as a
reserve practice model—and wasn't used. A pity, for all the twins packed up!
The machine was fairly conventional with a
close-ratio four-speed gearbox in unit with the motor and a deep sump to carry
the oil. A gear train to the camshaft was carried within the cylinder and head
finning in a cast-in tunnel, an unusual practice—another was a primary gear
train of three pinions, so that the motor spun the "right" way, with the clutch
on the centre pinion.
Obviously a lot of thought was put into the
design, the rockers had roller ends to reduce friction on the cam track and oil
jets squirted lubricant on to each cam. Four-rate hydraulic damping was provided
on the forks, and this was adjustable by a knurled knob on the top of each leg;
it was surprisingly effective and could be changed over in seconds. Another
practical point was the spare condenser for the coil ignition set carried
alongside the one in use on the front offside engine plate. This machine
illustrated was sold to a private owner in England in i960 and he often used it
at short-circuit meetings.
Engine: single-cylinder 250 c.c. o.h.c; light-alloy
cylinder and head; gear drive to camshaft. Ignition: coil and battery.
Transmission: gear primary drive to four-speed gearbox
in unit with engine; chain final drive. Frame: duplex cradle with pivoting-fork
suspension. Forks: telescopic with hand-controlled damping