Honda motorcycles opened for business in the American market in 1959, when the four-stroke 50cc Super Cub came on the market. And over the next 10 years the company acquired a very positive reputation, well deserved, for having high revving, hard hitting, highly dependable products, especially with its 305 series, like the CB77 Super Hawk and CL77 Scrambler.
But, as we say about horses, the 305s were getting a bit long in the tooth. What to do? Shouldn’t cost too much because lots of money was going into the carefully kept secret–the four-cylinder CB750. Having a different number would be good, from 305 to 350. The bore was increased from 60 to 64mm, the stroke reduced from 54 to 50.6mm, the true size of the “new” engine being only 325cc. No matter, as minor exaggeration is considered to be quite acceptable in the advertising world.
Honda used it in three models, the 1968 CB Super Sport and CL Scrambler, and a year later the SL Motorsport. All told, more than 600,000 of these 350s were sold in the U.S. over the six years of production, which means a lot of them are probably still stashed in old barns or forgotten behind the junk in the back of the garage. Here we are dealing with the Scrambler version, better characterized as a street-scrambler, having only minor pretensions to being competent off the pavement. It was a styling thing, much like the “adventure” bikes of today, with the rider liking to think that he can dash across the Gobi Desert any time he wants. Or, more likely, he wants other people to think that.
The essence of the scrambler style were those upswept pipes, curving individually around the left side of the cylinders and ending up in one large muffler that held a permanent spark arrester. Which was covered by a black heat shield for the first two years, and then the shield was chromed. Interestingly, the shiny header pipes were pipes within pipes, the ostensible reason being that the owner would not have to put up with the inevitable bluing that arrived with time. A secondary reason, which should really be the primary, was that the actual pipes carrying the exhaust were quite small in order to maintain a high exhaust-gas velocity that was essential to the tuning system.
This whole CL exhaust shebang weighed a substantial 24 pounds, and was responsible for a loss of several horsepower compared to its CB sibling, which had a longer, more efficient exhaust. Power was 33 horses at 9,500 rpm in the CL, compared to the CB’s 36 at 10,500, despite the engine internals being identical. CL owners usually ignored the redline on the tachometer dial.
Another Scrambler notion was the larger front wheel, 19 inches as opposed to 18. This was more about looks than performance, with the more serious off-roader, the SL, having a 21-incher. Front fender was slightly abbreviated, and the gas tank held 2.4 gallons, almost a gallon less than the CB’s. There were also rubber gaiters on the CL’s fork legs, always good for the daredevil look.
Those were the differences, now for the similarities. Looking into the powertrain, the parallel twin used alloy cylinders with iron liners, and the oversquare engine had lots of possibilities for revs–10,500 of them! In 1968 street-going four-strokes were not known for spinning ten thousand times a minute, and the less knowledgeable thought that this would mean a brief lifespan. But ten grand! How did they achieve that? First, there was a single overhead camshaft, spun by an endless chain between the cylinders. And the camshaft itself was a solid piece of work, weighing some three pounds.
But how does one get valves to seat properly at that speed? The valves all had dual coil springs, but the springs themselves were wound progressively, so that there was relatively less tension when the valve was seated, increasing greatly as the valve got pushed down. Carburetion was a pair of 26mm Keihin constant-velocity units using neoprene diaphragms.
The crankshaft, with four main bearings, spun using a 180-degree firing order as on the 305, but was a lot smoother due to excellent balancing. Primary drive was via straight-cut “paired” gears that were both efficient and quiet. Honda knew that the popular helical gears were quiet but not overly efficient, and came up with this mildly complicated system. A multi-disc wet clutch passed power through a five-speed transmission (up a gear from the 305) and out via a chain running along the left side of the rear wheel.
The chassis was not a notable construction, but suitable for delivering a good feeling to the rider. The backbone was a pressed-steel stamping, which was falling out of aesthetic favor at the time, though inexpensive to make. Fortunately it was hidden beneath the gas tank, and the viewable bits were mostly tubular, a single tube coming down from the steering head to spread into a double cradle.
Suspension was adequate, with a telescoping fork at the front and a pair of DeCarbon-type shocks at the back. A 3.00-19 tire was on the front wheel, 3.50-18 at the back. A double-leading shoe drum brake did yeoman’s service at the front, a single leading shoe at the back. It had 52 inches between the axles, and a wet weight of around 370 pounds.
The saddle, about 32 inches high, was long and flat, while the upswept handlebars had the mandatory cross-brace, part of the scrambler look. The rider saw separate speedo and tach above the headlight. Fenders were chromed, with excellent paint on the gas tank and side panels. And the essential electric leg for starting.
Price was $700, less than half that of the 750 four. Which is why these middling bikes outsold the big one…though we can only presume that quite a few 350 owners upgraded to the 750.
Source: RiderMagazine.com