Comparing the Honda S90 with its primary competitors, the Suzuki K11 Sport 80 and Kawasaki J1.
Years produced: 1964-1969
Power: 8hp @ 9,500rpm
Top speed: 62mph (claimed)
Engine: 89.5cc air-cooled OHC single
Transmission: 4-speed gearbox, chain final drive
Weight/MPG: 176lb (dry)/70-90mpg
Price then/now: NA/$700-$3,000
In the beginning came the Cub. Honda’s most easily recognizable motorcycle first hit the streets of the U.S. in 1958 and was an instant success, selling 24,000 units in its first five months. And while the step-through, 3-speed 50cc Cub worked perfectly for urban commuters, motorcycle enthusiasts, especially in the U.S., wanted more. Honda’s twin-cylinder range of CA touring and CB sport bikes was well established by 1964, but there was room in the market for something between the Cubs and the twins. Enter the Honda 90.
The first 90, the C200, arrived in 1963 with an iron cylinder and head, pushrod valve operation and a conventional 4-speed transmission instead of the Cub’s 3-speed automatic clutch unit. It also looked more like a traditional motorcycle, though with a pressed steel spine frame. Then in 1964 came the sporty S90 with an all-alloy engine and overhead camshaft.
Honda wasn’t the first motorcycle manufacturer to produce street bikes with overhead camshaft engines, of course, but Big Red did take them fully mainstream. The advantages of the design — a lighter, more direct valve train — meant Honda’s engines could be tuned for more power at higher revs, also making them more efficient. The downside was that overhead cam engines were typically more expensive to manufacture and valve clearances more difficult to adjust. Honda’s innovative design used a single chain-driven camshaft in the cylinder head operating the valves by a pair of rockers. Each rocker had a screw adjuster for straightforward valve adjustment.
The S90’s “over-square” (50mm x 45.6mm bore and stroke) 89.5cc engine was arranged with its iron-lined alloy cylinder almost horizontal, and capped with a light alloy cylinder head containing the single camshaft. The built-up crankshaft ran on two impressively large ball main bearings with a caged roller bearing big end. The “wet” sump held a quart of oil, which it kept clean with a centrifugal oil filter. Drive to the wet mutliplate clutch was by gears, passing from there to a 4-speed constant mesh gearbox with left side foot control (one down, three up). Final drive was by chain. Claimed output was 8 horsepower at 9,500rpm — an impressive rate compared with most of its contemporaries.
The compact drivetrain was bolted to a pressed steel beam frame. Front suspension was by hydraulically damped telescopic fork, with a swingarm with two spring/damper units at the rear. The chassis ran on 18-inch wheels front and rear, both with 2.50 x 18-inch tires and single-leading-shoe drum brakes. Ignition was by coil fed from an alternator and a 6-volt, 6-amp-hour battery, which also powered the lighting and other electrics. Slender, contrast-colored fenders and a streamlined gas tank with chrome side panels completed the sporty look. The list of standard equipment was impressive for a small bike, too, and included a large, replaceable-element air cleaner, turn signals, a tool kit stored under the seat, dual mirrors and a passenger grab strap. Although no tachometer was fitted, the maximum speeds in each gear were marked on the speedometer.
Weighing just 180 pounds dry, the S90’s 8 horsepower gave it a pretty lively performance. As tested by Cycle World in 1965, “A top speed of 65mph was achievable, with the all alloy engine remaining cool even at sustained maximum speed.” It was also miserly on gas, returning a claimed 176mpg (factory advertisement), giving the S90 a rather optimistic range of over 300 miles from its 1.84 gallon gas tank. A period anecdotal report puts the consumption closer to 90mpg with “spirited riding,” for a range of 165 miles.
The S90 is one of the machines that built Honda’s reputation for quality and reliability. Not surprisingly, it proved to be very popular in its day, and is now a collectible classic. To quote Cycle World, the S90 was (and still is) “… a remarkable little machine.” MC
1964-1967 Suzuki K11 Sport 80
Years produced: 1964-1967
Power: 7.3hp @ 7,000rpm/59.5mph (claimed)
Engine: 79.5cc air-cooled 2-stroke single
Transmission: 4-speed, chain final drive
Weight/MPG: 154lb (dry)/153mpg (factory ad)
Price then/now: NA/$300-$1,100
Suzuki entered the U.S. market in 1963 with a six model range that included the 80cc K11 Sport 80. Like the S90, the K11 used a pressed steel spine frame, but added a single front downtube. A telescopic “oleo” front fork handled front suspension duties, while a pressed steel swingarm and dual shocks handled the rear. Wheels were 2.25 x 17 inches front and rear with single-leading-shoe drum brakes.
Under the hood was a 79cc air-cooled, piston port 2-stroke single with an iron cylinder, alloy head, gear primary and 4-speed transmission. Fuel required was 20:1 gas/oil premix at first, soon replaced by Suzuki’s Controlled Crankshaft Injection oiling system. Sporty touches included a high-level exhaust and exposed fork springs, though a rear luggage rack was also included.
The Sport 80 (and the 50cc M12 Sport 50) sold in large numbers (at least half a million were built) and established Suzuki’s reputation for lively, well-made motorcycles.
1965-1968 Kawasaki J1
Years produced: 1965-1968
Power: 7.5hp @ 6,800rpm (J1, J1D, J1L); 7.8hp @ 7,000rpm (J1T, J1TL); 8hp @ 7,000rpm (J1TR, J1TRL)/56mph (J1L)
Engine: 81.5cc air-cooled 2-stroke single
Transmission: 4-speed rotary shift, chain final drive
Weight/MPG: 168lb (dry/J1L)/188mpg (factory ad)
Price then/now: NA/$600-$1,600
Built to a specification superficially similar to the Suzuki K11 was Kawasaki’s J1 range. The main difference: a rotary disc-valve intake system. This fed the 81.5cc alloy head 2-stroke single driving an unusual 4-speed transmission, also known as a “rotary shift.” Gear selection went N-1-2-3-4-N, continuously! It was a setup that confused many first-time Kawi pilots. The engine attached to a pressed-steel frame running on 2.50 x 17-inch wheels with a telescopic fork at the front and a spring/damper controlled swingarm at the rear.
Over its life, the J1 was available in a number of specifications. The base J1 drank a gas/oil premix, as did the electric-start J1D.
The J1L added Kawasaki’s Superlube oiling system, the J1T/J1TL came with a high-level exhaust, dual seat and white wall tires, while the J1TR/J1TRL were fitted with offroad tires and a sprung front fender. The J1 range was replaced in 1969 by the 90cc G3 models.