Honda CB 750F Turbo Modified

Turbocharging is what the world is coming to. More horsepower-efficiency is the goal, and turbos offer a more elegant and direct means to that end than multiplying valves, changing combustion-chamber shapes and grinding radical cam profiles. What's more, the gain in performance is almost free, since a turbocharged engine uses its own exhaust gases to drive a compressor that force-feeds the motor its fuel-air mixture, producing more punch per power pulse.

That's why you should think of turbocharging as artificial respiration for a generation of engines suffocating in mechanical complexity.
With that vision of the future in mind, the staff of cycle guide bolted together its own version of today's ideal street turbo, using a combination of R.C. Engineering's new real-world turbo technology and Honda's good-handling CB750F. The result is not revolutionary, but it represents a major step along the path to a turbocharged tomorrow.

Because this is not a futuristic race bike, even though the Porsche-red paint pumps the adrenaline and the turbo script on the sidecovers stirs emotion within everyone from punks on RD400s to bankers in Mercedes-Benz Turbo Diesels. No, this bike is more than just another rabid refugee from the drag-strip; it's a manageable street bike, and that's a first for turbocharged motorcycles.

Make Model : Honda CB 750F Turbo
Year : 1980
Engine : Air cooled, four stroke, transverse four cylinder, DOHC, 4 valve per cylinder, Turbo churched
Capacity : 748
Bore x Stroke :: 62 x 62 mm
Compression Ratio 9.0:1
Induction : 4x 38mm R.C. Engineering butterfly-type,
Ignition  /  Starting : CDI  /  electric
Clutch Wet. multi-plate
Max Power : 72 hp @ 9000 rpm
Max Torque : 67 Nm @ 7000 rpm
Transmission  /  Drive : 5 Speed  /  chain
Gear Ratio 1 253 15.41 4.9  /  II 1.79 10.88 6.9  /  III 1 39 846 8.9  /  IV 1.16 7.06 10.7  /  V 096 5.86 128
Front Suspension : Adjustable telehydraulic fork.
Rear Suspension : Swinging arm fork with adjustable shocks absorbers.
Front Brakes ; 2x 300mm discs
Rear Brakes : Single 328mm disc
Front Tyre : 3.50 H19
Rear Tyre : 4.50 H17
Seat Height 28.5 in.  /  724mm
Wet-Weight : 523 lbs  /  237kg
Fuel Capacity  : 20 Litres  /  5.3 gal
Consumption  average : 27 to 39 mph  /  11.5 to 16.6 km/I
Standing ¼ Mile  : 11.99 sec  / 113.8 mph 183 kph

COMPARATIVE TEST DATA:
Make Quarter-Mile, sec mph Top Speed, mph Weight, lb* Stopping Distance From 60mph, ft.
Turbo Honda CB750F 11.99/113.8 NA 523 135
Honda CB750F 12.41/106.8 128 524 134
Kawasaki KZ750 12.50/107.8 127 471 ' 134
Suzuki GS1000ET 11.98/113.9 136 528 137
Suzuki GS1100ET 11.43/118.3 140 544 116
Yamaha XS1100SG 11.94/112.6 135 572 129

With a couple twists of the throttle to let the accelerator pump prime the engine, the Turbo Super Sport fires up readily, and after a few minutes it settles into the fluctuating idle peculiar to turbo bikes.

The unruly growl from the exhaust pipe and the heat cascading from the cylinder head might tempt you to think such a bike should be lit off only on special occasions; but you can snick this motorcycle into gear and embark upon an expedition into city traffic without fearing that it will load up and die at the first stoplight and melt into an expensive heap of slag by the third. The huge carburetor requires that you do not grab a handful of throttle frivolously, but on the whole you can treat this bike like a motorcycle instead of a beast and live to tell about it.

And yet the turbocharger boosts the F-model into a new dimension of hyper-speed. Crank the throttle on and the turbo comes up on boost at 3500 rpm, feeding the 16-valve 750 with enough potential energy to enable the Honda to keep pace with lit-erbikes, even with just six psi of boost. Power arrives with a predictable sustained rush that makes the blood surge to the back of your cranium and yet proves perfectly controllable. As powerful as the Turbo Super Sport is, you never feel disoriented, as if the turbo had triggered a reactor melt-down beneath you. As a result, you can put your turbo-power to use on winding roads as well as on Burnout Boulevard.

The F-model still glides through left-right-left transitions with an effortlessness that makes you feel invulnerable, and it's sensitive and willing at every turn—but now at a higher speed. The simple 750cc street bike beneath you suddenly has acquired new muscle.
It's the combination of low-speed docility and high-speed potency that makes turbocharging the topic of discussion among motorcycle engineers. Because a turbo ideally should provide an engine with flexibility unattainable by conventional means, as if its power curve had suddenly been boosted upward along its entire length. At cycle guide, we're fascinated by turbocharging for the same reason. Yet we also know that previous turbocharged motorcycles have compromised flexibility. Warm-up times were long, frequent plug changes were necessary, boost didn't arrive until the tach had swept two-thirds of its way across the dial—and once it did, the front wheel inexorably rose skyward. We weren't satisfied with turbo bikes calibrated for the racetrack. We wanted to create a turbo street bike.