| The
1975 version of the TZ500 with the monoshock rear suspension.
Note the Finnish flag on the fairing. It signified the bike
as that used by Giacomo Agostini's Finnish team-mate - Teuvo
Lansivouri. |
Among
the Japanese motorcycle companies, it was always Honda which managed
to get into the act when it came to Grand Prix racing. Honda was
the dominant force in GP racing in the 1960s and when it unleashed
its 500cc four cylinder bikes in the hands of the late Mike Hailwood
and Jim Redman, they came oh so close to bringing the 500cc rider's
world championship to Honda. But it wasn't to be.
Honda retired from top flight world championship GP racing at the
end of the 1967 season and they didn't return until the early 1980s
with Mick Grant on the oval-piston four stroke NR500 which was an
unmitigated disaster. However the world no. 1 bike maker finally
did what was unthinkable - build a two-stroke 500cc machine on which
Freddie Spencer finally won Honda's first 500cc rider's crown. To
Yamaha however went the honour of not only bagging the first ever
500cc rider's world championship title - the first Japanese bike
maker to achieve this, but also being the first in the history of
the sport to do it on a two-stroke machine! The seeds for Yamaha's
move into the premier blue riband class of bike sport were sown
when engineers decided to couple two of the firm's liquid-cooled,
twin-cylinder TZ250 motors to come up with a 500cc four. This engine
was a simple (if at all it could be referred as such then!) piston-ported
design with a single petal reed valve. The first 500 engine was
run in July 1972, and the machine, model number OW20, was tested
in December by old Yamaha hand Moto Hashi. Designed by chief designers
Naito and Matsui, the two-stroke four produced 80bhp at 10,000rpm
and could reach 165mph.
This wasn't Yamaha's first four-cylinder two-stroke though. In 1968
it had raced a 250cc vee-four which was an incredible piece of engineering,
dishing out 73bhp at a shade over 14,000rpm, sported an 8-speed
gearbox, twin ignition systems and an autolube system. A 500 was
on the cards but at the end of the 1968 season the FIM played spoilsport
and banned four-cylinder machines from the 250cc class in order
to keep the costs of racing low. Yamaha pulled out of World Championship
Grand Prix racing as a works team but crucially continued to supply
bikes like the TD1s and TD2s plus their liquid-cooled successors
the TZ250s to privateers. However the competition department had
kept its hand in and thus was born the Yamaha 500cc challenger.
In early tests, the reed valve inhibited maximum flow into the crankcases
and for a while the reed valves were junked for tuned inlet tract
length intakes. By designing the engine with the correct distance
from the crankcase to the bell mouth of the carb, the shock wave
that travels backwards and forwards along the tract could be employed
as a valve that would ensure little gas could escape from the engine.
However, the reed valved engine was used in the TZ500's first race
and the men entrusted with the job of spearheading Yamaha's foray
into the premier class were Finn Jarno Saarinen and veteran Japanese
rider Hideo Kanaya.
The race was the French GP in April 1973 and Saarinen was brilliant
on the machine which featured twin rear shocks, twin discs up front
and a single disc at the rear. He just ran away from the pack beating
Phil Read on the MV Agusta quite comfortably. To make it a notable
debut for the maker and its machine, Kanaya came home third. In
the next GP, the Austrian, atrociously wet weather prevented Saarinen
from repeating his performance from France but Kanaya was second.
Jarno was leading the German GP when he had to retire and just a
week later while competing in the 250cc Italian GP at Monza, Saarinen
crashed and the favourite for the 1973 500 title was killed. Yamaha
withdrew then and went back to improve the bike and seek another
rider. They got one in the form of 14 times World Champion Giacomo
Agostini. Ago took two wins in 1974 on the redesigned bike, now
with Yamaha patented 'monoshock' rear suspension and in 1975 the
Italian finally gave a Japanese bike maker its first 500cc rider's
crown.
|
