Mid-Size Commuter Bike: 1974-1979 Kawasaki KZ400

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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
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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.

Overall, it was considered an impressive package. “Ride the KZ400, even if only around the block, and you’ll know it was designed to do things the way the CB350 did — only a little better,” said Cycle. Most testers liked the overall smoothness and even power delivery of the engine, though some buzzing occurred at higher revs. The KZ started easily hot or cold and the transmission was vice-free. The steering was nicely neutral on even surfaces thanks in part to the sturdy double-cradle frame. But it was the KZ400’s suspension that really came in for criticism.

 “We think the front suspension is inadequately damped … most of what the fork legs might be doing or failing to do gets obscured by the commotion back at the rear wheel … a ferocious hopping can be provoked with hard application of the front brake,” said Cycle, adding that “very nearly all that can be said of the KZ400’s rear shocks is that they do provide a convenient strut mounting for the springs.” They were, concluded Cycle, “overwhelmingly, miserably, abominably and infuriatingly cheap.”

It was an issue Kawasaki never satisfactorily addressed over the five-year run of the KZ400, though there were other changes: an external oil line to the cam box stopped oil leaks from the cylinder head joint; the eccentric rocker spindles gave way to conventional screw adjusters; the transmission got an extra cog, making six gears; the carbs went from 36mm to 32mm (losing a couple of ponies, but improving fuel consumption); a better front brake with greater swept area; and an ingenious auto-retracting kickstand (triggered by the drive chain) was fitted.

Reviewing the final year’s model in 1979, Cycle World seemed to have a somewhat mixed opinion of the bike: “Kawasaki has improved the KZ400. Problems have been eliminated. Convenience has been added. There is still a way to go. Even commuters deserve better suspension. A more comfortable seat would be nice. It’s an easy to use motorcycle, which would seem to be just what commuters have been asking for.” MC

Contenders: Two-cylinder rivals to Kawasaki’s KZ400

1978-1981 Honda CB400T Hawk
Claimed power: 36hp @ 9,500rpm
Top speed: 100mph
Engine: 395cc air cooled SOHC parallel twin
Weight: 401lb (wet, T2)
Fuel capacity/MPG: 40-50mpg
Price then/now: $1,300 (T2, 1978)/$750-$1,500

Almost every Under the Radar includes a Honda: often, it’s the benchmark bike. The CB400T is no exception. A brand new design owing nothing other than its parallel twin format to the previous 180-degree, 2-valve CB360, the Hawk used a 360-degree crank with chain driven balance shafts. A single exhaust and two intake valves per cylinder were operated by a single overhead cam, with the cylinders fed by a pair of 32mm Keihin CV carbs. Drive to the 5-speed tranny (1979-on had a 6-speed) was by straight-cut gears. The power unit was suspended from a pressed-steel spine frame holding conventional telescopic forks and dual rear shocks. The Hawk was initially available as the fully-equipped CB400T2 and the stripped T1, which lacked the 2’s ComStar wheels, disc front brake, electric starter, tachometer and centerstand. However, it was 21 pounds lighter, held almost a half gallon more fuel — and was $200 cheaper!

Cycle magazine’s only complaint about the Hawk was some driveline lash and surging on throttle transitions. Their testers were particularly impressed with handling and suspension, though they were less keen on the styling, commenting that “they might appear pedestrian, but as motorcycles they function beautifully.” Cycle Guide said that “the Hawks would seem to offer the best combination of performance, handling, braking and maintenance-free enjoyment in their class.”

1976-1982 Yamaha XS400
Claimed power: 32hp @ 8,500rpm
Top speed: 96mph
Engine: 391cc air-cooled SOHC parallel twin
Weight: 391lb (dry)
Fuel capacity/MPG: 50-60mpg
Price then/now: $1,348 (1977)/$750-$1,500

By the time Honda joined the 400 twin party, Yamaha, Kawasaki and Suzuki had already arrived (Suzuki notably with a DOHC engine). Yet the electric-start XS400F looked more modern, with cast alloy wheels and disc brakes fore and aft (like Honda, Yamaha introduced an economy drum braked, spoke wheel, kickstart only version for 1979). Between the wheels was a 180-degree crank, SOHC, 2-valve 400cc twin fed by dual 34mm Mikuni CV carbs. Drive to the 6-speed transmission was by straight-cut gears.

With no balancer shaft, the Yamaha was “the roughest running 400 4-stroke twin on the market,” said Cycle World, noting its buzzing made the mirrors useless at speed. But the engine started easily hot or cold, and had smoother throttle response than its competition. CW found the gearshift occasionally balked and the clutch sometimes grabbed and dragged when hot. Front suspension was compliant, though the rear “beat the rider’s kidneys.”

The Yamaha was generally quicker than the KZ400, but slower than the Hawk. Braking was excellent, though the rear disc could lock easily. Cycle magazine summed it up: “The XS is neither the fastest in its class, nor the least expensive, nor the most comfortable. It is nevertheless a handsome, functional and economical motorcycle — easy to maintain, miserly with gas, and still competitive in a hotly contested class.”

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