CLASSICS
WORDS AND PHOTOS:
Rhys Jones
SIX OF THE BEST
Last 250-350-six 1969
F
ifty-six years ago, a twenty-four year
old engineer called Soichiro Irimajiri
presented a set of drawings to Honda’s
massive Research and Development
department. The drawings were the
beginning of the remarkable six-cylinder
RC166 250cc, and RC174 297cc 350 racing
engines. Irimajari, one of Japan’s finest
young engineering graduates, had already
played a leading role in the development of
the remarkable 50cc eight-valve twin.
The six-cylinder motor was Honda’s
response to the growing two-stroke
competition. In order to compensate for
having half the number of firing strokes, the
four-strokes needed better breathing and
to spin faster. This meant multiple, small,
short stroke cylinders. The motor had 24
valves, six carburettors, and seven gears.
Peak power was 60bhp at 17,000rpm.
78 KIWI RIDER
These machines were considered to be
the most complex and technologically
advanced motorcycles to emerge from the
mid-60s Golden era of road racing. Judging
by the specs it is very difficult to imagine a
rush to produce road-going motorcycles of
this complexity, and cost to manufacture.
Racing, however, was different. What
was learnt from the race track did often
translate into competitive machinery for the
road, and at this stage Honda seemed to
understand that winning races was excellent
for the company’s profile. Honda in fact
needed a tonic to beat the competition
on the race track, increase prestige in the
showroom and, of course, sell more Hondas
as a consequence.
Honda’s response to the domination at race
meetings by 250cc two-stroke Yamahas,