HONDA
NR750
The
unique Honda NR750
was a bike that only Honda, the world's largest, boldest
and arguably also most stubborn motorcycle firm, could have built.
Gloriously stylish and technically advanced but complex, heavy and
hugely expensive, it was inspired by the NR500 grand prix racer of
the late 1970s and early '80s. Like the racebike, the roadgoing NR
was most notable for its 'oval' pistons, each with two conrods, two
spark plugs and no fewer than eight tiny valves.
There
was much more to the Honda NR750 than its piston shape. The bike was
visually stunning, with a futuristic twin-headlamp full fairing and
matching tank-seat unit that was made from a blend of carbon-fibre
and fibreglass, and was rumoured to cost more than any other complete
mass-produced superbike. The paint finish was outstanding; the
titanium-coated screen alone was hugely expensive.
The
chassis was of similarly high quality, although its design was
relatively conventional. A rigid twin-spar frame of polished
aluminium held a Pro-Arm single-sided swingarm, similar to that of
the
RC30. The front end specification included 45mm diameter Showa
upside-down front forks, a 16-inch front wheel, and large twin brake
discs gripped by four-piston calipers.
But
it was the 748cc V4 engine that was in every way the NR750's main
attraction. The liquid- cooled, 32-valve motor's cylinders were set
at 90 degrees, with gear drive to the twin overhead camshafts. The
eight conrods were made of lightweight titanium. Fuel was delivered
by a sophisticated
injection system. The complex exhaust system ended in twin high-level
silencers in the tailpiece.
The reason
for the Honda NR750's existence was that Honda was keen to utilize some of
the technology that had been developed more than a decade earlier for
the NR500 racer. Back then, there had been a valid technical reason
for using oval pistons (in fact they were shaped like a running
track, with straight sides and semi-circular ends), following Honda's
decision to take on Suzuki's and Yamaha's two- strokes with a
four-stroke.
HONDA
NR750
Characteristics
of a V8
Honda's
successful grand prix bikes of the 1960s had been high-revving
four-strokes, many of them small-capacity multis with four valves per
cylinder. By 1979, 500cc GP bikes were limited to four cylinders, so
Honda developed the NR as the nearest they could get to a V8. Despite
costing billions of yen the 'Nearly Ready' was never competitive, and
it was abandoned in 1981.
There
was no comparable incentive to use oval pistons on a roadster, but
the high-revving NR was the world's most powerful 750, with a peak
output of 125bhp at 14,000rpm. Top speed was 160mph (257km/h), and
the V4 also had an outstandingly broad spread of torque. But despite
extensive use lightweight materials the NR was heavy, at 4891b
(222kg), and accelerated no harder than much cheaper 750cc rival,
HONDA NR750 |
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