The Honda CB750: A Technical Milestone in Motorcycle Engineering

The launch of the Honda CB750 in 1969 marked a seismic shift in motorcycle engineering. Known as the world’s first mass-produced superbike, the CB750 introduced performance, reliability, and manufacturing precision previously reserved for exotic or race-bred machines. Its impact was not only commercial but deeply technical, forcing a complete reevaluation of design standards across the motorcycle industry.

Engineering Philosophy and Development

Developed under the guidance of Soichiro Honda and project lead Eiji Kawakami, the CB750 was a response to growing demand—especially from the U.S. market—for a large-capacity, high-performance motorcycle that could rival British twins and American V-twins. Honda’s vision was rooted in precision engineering: reduce vibration, increase reliability, and integrate features that had never been available in a single production motorcycle.

Key to this was the decision to use a transversely mounted, air-cooled inline four-cylinder engine with a single overhead camshaft (SOHC) operating two valves per cylinder via rocker arms. The 736cc engine used a slightly undersquare configuration with a bore and stroke of 61.0 mm × 63.0 mm, optimizing midrange torque and mechanical balance.

The engine was mounted in a tubular steel duplex cradle frame, using four mounting points to maintain rigidity and reduce torsional flex under load. This frame design was critical in supporting the CB750’s unprecedented combination of speed and smoothness.

The Engine: Precision and Innovation

The CB750’s four-cylinder engine delivered approximately 67–68 hp at 8,000 rpm and redlined at 8,500 rpm. It featured:

• Four 28 mm Keihin round-slide carburetors

• Horizontally split crankcases to improve oil sealing

• A 180-degree crankshaft configuration for smoother power delivery

• Gear-driven primary drive with a wet multi-plate clutch and 5-speed constant mesh gearbox

  
  

The ignition system included four contact breaker points and twin coils—one for cylinders 1/4 and another for 2/3—housed behind a chrome cover on the engine’s right-hand side.

Braking and Suspension

The CB750 was the first production motorcycle equipped with a hydraulic front disc brake, using a 296 mm rotor and twin-piston caliper. This provided stopping performance that far exceeded the drum-braked competition.

At the rear, a conventional 180 mm drum brake was fitted. Suspension included 31 mm telescopic front forks and dual coil-over rear shocks with preload adjustment. Wheel sizes were 19 inches front and 18 inches rear, running 3.25-19 (front) and 4.00-18 (rear) tires on spoked rims.

Electrical System and Controls

The CB750 used a 12-volt electrical system, and it introduced several rider aids uncommon at the time:

• Electric start

• Handlebar-mounted kill switch

• Neutral indicator light

• Self-cancelling turn signals

• 150 mph speedometer and 10,000 rpm tachometer with warning lights

  
  

From Sandcast to Die-Cast

Initial CB750s produced in 1969 used “sandcast” engine cases—technically gravity die-cast into sand-core molds. These thicker, rough-finish cases were used for the first ~7,400 units until Honda transitioned to high-pressure die-casting for mass production.

Sandcast CB750s are now highly collectible due to their rarity and historical significance.

Performance and Influence

The CB750 delivered a top speed of over 120 mph and could run the quarter-mile in approximately 12.4 seconds. More importantly, it did so with minimal vibration, dependable starting, and virtually leak-free operation—transformative qualities at the time.

It forced legacy manufacturers like Triumph, Norton, and Harley-Davidson to reevaluate their offerings, and it inspired a new wave of “Universal Japanese Motorcycles” (UJMs) from Kawasaki, Suzuki, and Yamaha.

The Legacy of the CB750

The CB750 remained in production in SOHC form until 1978, when it evolved into the DOHC CB750F. But the legacy of the original is unmistakable.

This was a machine that proved you could mass-produce high performance and high quality without sacrificing affordability or reliability. Its engineering precision, combined with everyday usability, changed what motorcyclists expected from a bike—and what manufacturers had to deliver to stay relevant.

The Honda CB750 wasn’t just the first superbike—it was the superbike that redefined the rules for all that followed.