Forty-Inch Flyer: 1977-1980 Kawasaki KZ650

Comparing the Kawasaki KZ650 to its primary 650cc 4-cylinder competitors, the Honda CB650 and the Suzuki GS650E.


Kawasaki KZ650
Years produced: 1977-1980
Power: 49hp @ 8,000rpm (at rear wheel/period test)
Top speed: 108mph (period test)
Engine: 652cc air-cooled, DOHC inline four
Transmission: 5-speed, chain final drive
Weight (wet)/MPG: 498lb/44mpg (avg./period test)
Price then/now: $1,995 (1977)/$700-$2,200

In marketing-speak it’s called a “unique selling proposition,” or USP. It’s the feature or benefit that makes your product stand out from the rest. In the era of the ubiquitous Universal Japanese Motorcycle – across the frame, air-cooled, overhead cam 4-stroke multi – each of the Big Four knew they had to be in this market: But how to give their UJM a USP?

Honda set the stage with the single overhead cam CB750. Kawasaki fired back with the dual overhead cam 900cc Z1. Honda tried the undercut with 350, 400, 500 and 550 fours. Suzuki made the first dual overhead cam 750, the GS. Yamaha tried a triple. Kawasaki responded with a new capacity: 650cc (40ci).

Kawi asked Z1 designer Ben Inamura to develop the KZ650. And while the Z1 inherited some engine design features from Kawi’s strokers (like the built-up crank), Inamura started with a clean slate for the KZ650. The goal: a 650 that could run with the 750s, while making the engine mechanically quieter and easier to mass produce than the Z1.

The 650 used a one-piece crank with five shell main bearings and split connecting rod big ends (whereas the Z1 had roller bearings and one-piece connecting rods on a built-up crankshaft). A chain and central sprocket drove the two overhead camshafts, running directly in the cylinder head (they ran in shell bearings in the Z1). The cams operated the valves directly, with adjustment by shim under bucket (Z1: shim over bucket). A 24mm Mikuni fed gas to each iron-lined alloy cylinder and the spark plugs were fired by two coils via mechanical contact breakers. A car-type, controlled-field, crankshaft-mounted alternator (Z1: permanent magnet) and regulator/rectifier generated 12 volts. Starting was electric with kickstarter backup. Primary drive was by HyVo chain to a jackshaft (Z1: direct geared) with integral cush drive, carrying the starter and oil pump, then by straight-cut gears to a multiplate clutch and 5-speed gearbox.

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I had a blue KZ650 purchased new at Kawasaki West on Colfax Avenue in Denver on Memorial Day weekend in 1978. I traded a 69 Triumph Trident as a downpayment. They blew up the Triumph gearbox while I was signing the sales contract. They complained a little, but it was already a done deal. I put 10k miles on that bike carving the canyons west of Denver between Memorial Day and Labor Day 1978. My favorite was Golden Gate Canyon, as I was a summer student at CSM. I only really learned to ride that summer, even though it was my third bike. While my knee dragging days are long over, I bought a retro 2014 CB1100E with Yoshi pipes a couple of years ago to relive my youth a little. I love it.

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