Mid-Size Commuter Bike: 1974-1979 Kawasaki KZ400

By The Motorcycle Classics Staff
Published on February 12, 2015
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In England, the Kawasaki KZ400 was sold as the Z400. This is a 1978 6-speed.
In England, the Kawasaki KZ400 was sold as the Z400. This is a 1978 6-speed.
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1978-1981 Honda CB400T Hawk
1978-1981 Honda CB400T Hawk
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1976-1982 Yamaha XS400
1976-1982 Yamaha XS400

1974-1979 Kawasaki KZ400
Claimed power: 35hp @ 8,500rpm
Top speed: 93mph (period test)
Engine: 399cc air-cooled SOHC parallel twin
Weight: 399lb (wet)
Fuel capacity/MPG: 50-60mpg
Price then/now: $1,170 (1974)/$750-$1,500

Just as Kawasaki aimed the 1973 Z1 squarely at Honda’s CB750, they also tried to out-Honda Honda in 1974 with the KZ400, their take on the best-selling CB350. As with the Z1, they leapfrogged Honda with more capacity, but stopped short of upping the ante further by giving their new little KZ400 the Z1’s dual camshafts. Why?

The answer may be the intended purpose of the KZ400. While the 903cc Z1 threw down the performance gauntlet, the mid-size KZ400 twin was designed as an economical, easy-to-ride, unintimidating commuter bike — and it arrived just in time for the 1973 oil crisis. Under an Arab embargo, the price of crude oil rose fourfold between October 1973 and March 1974. Suddenly, fuel consumption became really important.

Delivering around 60mpg, the KZ400 was certainly economical, and it would also comfortably keep up with traffic, especially at the then mandatory maximum 55mph highway speed. And while a 15-second quarter-mile time wasn’t exactly blistering, it would leave all but the most muscular gas-guzzling cars sitting at the stop sign. But was the KZ400 just a bigger-inch CB350 clone?

The KZ400 engine used mildly over-square dimensions of 64mm bore and 62mm stroke for 399cc. The 360-degree crank (the CB’s was a 180-degree) ran on four plain main bearings with a manually adjustable central chain driving the single overhead camshaft, which operated the four valves by rockers on eccentrics. (Rotating the rocker spindles allowed for valve adjustment.) And while the 360 crank produced smoother power pulses, just like British twins, the format invited vibration. Kawasaki fixed this in the 400 with maintenance free, chain-driven balance shafts. Lubrication was wet sump and ignition by a single contact breaker with a dual-output coil firing both cylinders.

A pair of 36mm Keihin CV carburetors fed the two cylinders, which exhausted with the aide of an equalizer chamber cast into the head. Drive to the wet multiplate clutch and 5-speed transmission was by Hy-Vo chain, with 530 chain final drive. The powerplant was installed in a conventional but solidly built mild steel tube frame with a telescopic fork and a twin-shock swingarm rear end. Brakes were a single floating two-pot caliper disc front and single-leading-shoe drum rear. Equipment included electric start (with kickstart backup), external gear position indicator, crankcase oil level sight glass, and a warning light for a blown stoplight bulb, as well as separate tachometer and speedometer with trip meter.

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