Kawasaki was the last of the Big Four Japanese OEMs to enter the U.S. market, setting up shop in greater Los Angeles in 1966 with a couple of tiddlers, an old-fashioned British-style OHV 650cc parallel twin and a very nice 125cc two-stroke single identified rather unromantically as the B8. The Kawasaki marketing boys (don’t know if any girls were involved) soon came to appreciate the use of a catchy name, and when the 250cc two-stroke twin, the A1, went on the market that year, it was called the Samurai—a brilliant choice. And a brilliant motorcycle, with rotary valves, a new concept on the street.
Realizing that the go-fast part of the motorcycle world was quite profitable, Kawasaki upped the ante, or we could say “cylinder capacity,” within a year, and did it with a vengeance—or maybe avenge-ance. When the 350cc Avenger two-stroke twins, the low-pipe A7 and high pipe A7SS (Street Scrambler) got to the American market in 1967, everybody was impressed.
Despite lighthearted denials from the company, the 350 (bore 62mm, stroke 56mm = 338cc) was essentially a bored-out version of the 250, but with significant improvements. The Avenger engine was like the Samurai’s, a rotary disc-valve twin, with valves operating off both ends of the crankshaft. Instead of the 250’s 22mm carburetors, the 350 had two 26mm Mikuni MV carbs sticking out the sides—best not to lay this baby down at speed. End to end, the engine was almost a foot and a half wide. Four main ball bearings supported the crankshaft and provided a sound seal between the pistons. The primary gears spun the generator that was mounted inside the air-intake casting behind the cylinders, which kept a cool flow running over the AC unit. The generator also served to fire the points in a very reliable manner, better than being at the far end of a slightly wandering crankshaft. Capacity discharge ignition was added in 1969.
Lubrication was improved, the 250 merely mixing oil with the gas at the intake ports, while the 350’s new Injectolube system metered oil going directly to the intake ports and added direct oiling, under pressure, to all the bearings and rod connections along the crankshaft. The “control cable,” as it was called, ran from the throttle to the two carbs, and a third line went to the oil pump.
The new oiling system had a direct correlation to the factory-advertised power, which went up some 30 percent, from 31 horses on the 250 to 40.5 on the 350. This was good for a quarter-mile time of less than 15 seconds and a top speed of more than 100 mph. In best advertising fashion, the ads exaggerated a bit, claiming a quarter-mile time of 13.8 seconds and a top speed of 115 mph—though no magazine tester could equal those numbers. Maybe a 90-pound rider with a strong tailwind had achieved it. Max power came out at 7,500 rpm, but since there were no valves to bend, misguided enthusiasts would easily run it to 9,000. All this from a stock 350 costing a reasonable $850…buyers had no complaints.
Power went through a wet clutch and five gears—with neutral at the very bottom. The gearbox had its own separate oil supply, and a change was recommended every 1,800 miles. Another bit of two-stroke maintenance was to take the heads off at that same mileage and scrape off the built-up carbon with a wire brush. Do the top of the pistons, too. And don’t forget to take the baffles out of the exhaust pipes and clean those, too. Two-strokes had a lot of emissions, which is why the EPA later banned them.
The steel frame, a weighty but justifiably strong piece, was tubular, the cradle running wide as it went under the engine and reinforced by cross braces where needed. Kawasaki seemed to have found a reasonable balance between around-town and racer-road when it came to handling, with the motor being firmly gripped. Up front, the telescopic fork provided adequate spring rates and damping, with rubber boots covering the chromed sliders. The SS had both a friction damper and a little hydraulic rod to control any untoward movement. At the back, chromed shock springs were left uncovered, always an eye-catcher, with three-way adjustability. Eighteen-inch wheels were fore and aft, with a 3.25 tire at the front, 3.50 at the back. A double-leading shoe brake did a good job on the front wheel, with a single-cammer at the back.
Between the axles was a rather short 51 inches, all the better to flick through those tight curves. And the curb weight, with five pints of oil and 3.5 gallons of gas, was a respectable 340 pounds.
The look of the SS was one to catch the eye. The public loved those upswept exhausts, with perforated heat shields offering protection to the rider and passenger, chromed fenders (the rear one slightly bobbed to enhance the sporty look), chromed panels on the gas tank, chromed exhaust and well-done paint on the tank, side covers and headlight nacelle. A nice, flat saddle could easily hold two people.
The nicest aspect of the Avenger was that with a flexible engine, the rotary design gave a much wider usable range of power as compared to a piston-port engine. The rider could drop the revs down to 2,000 rpm and have a pleasant, quiet ride through town. While out on the back roads those two pistons would create a real screamer at 7,000 or more rpm. Not many of us can remember the sound of a two-stroke twin at full rip, but it is impressive.