Retrospective: Honda CL72 Scrambler 250: 1962 – 1965
November 11, 2011
Filed under Retro + Vintage Motorcycle Reviews
photography by Steve Ready
[This Retrospective: Honda CL72 Scrambler 250: 1962 - 1965 was originally published in the December 2011 issue of Rider magazine]
In the early ’60s big changes were coming to the motorcycle world. The British industry did not understand that it was on death row, Harley was grudgingly modernizing its bread-and-butter big twin, and the European manufacturers were thinking about getting out of the utilitarian and into the sportier bikes. Everybody looked to Japan, with the smart ones figuring that this would soon be the real competition, the not-so-smart wanting to believe that the oriental mind would build only tiddlers.
The Japanese designers, and marketers, were well ahead of the game. Especially when it came to divining the wishes of the American buying public, obviously the most lucrative market when it came to selling modestly priced playthings. Honda had set up business here in 1959, and its big bike was the 250 Dream, although its angular styling was, in a word, awkward. As a commuter bike it had the grime-reducing benefit of heavily valanced fenders and big side panels, with the rectangular headlight and pressed-steel leading-link front fork certainly lacking the sporty look.
All that would change when the 250 Hawk appeared in 1961. What a difference skinny fenders, minimal side panels and a genuine telescoping front fork did to the image. And to the sales; Americans definitely liked the semi-racer approach.
What next? The sales experts, looking at what was selling in the British lines, realized that street-going motorcycles with upswept pipes and the aura of off-road mastery were also big. All right, a street-scrambler model was in order. This required more serious work than was done turning the CA72 Dream into a CB72 Hawk, as modifications to the chassis would have to be made for the CL72 Scrambler.
The engine would stay the same. And what an engine it was, an all-alloy parallel twin with a single overhead camshaft opening two valves per cylinder. The cylinders were perfectly square at 2.12 inches, as the old road tests reported, or 53.8 millimeters, as we would write today. Two 22mm slide-operated carburetors, made by Biliath, fed fuel to the cylinders, where it was compressed 9.5 times, with an output claimed to be 24 crankshaft horsepower at 9,000 rpm. And dependable at those speeds, due to the fact that the pressed-together crankshaft was running on four bearings, ball bearings on the ends, roller types in between. The connecting rods used needle bearings. The cam was spun by a chain running off a sprocket placed between the cylinders, using a roller-type tensioner that was adjustable externally. The centralized location kept everything in proper balance, and the pistons went up and down at 180 degrees to each other. One choice engineering decision had been to split the crankcases horizontally, rather than vertically, meaning there were no leaks for the oil in the wet sump.
To demonstrate how truly talented the Japanese could be, in 1962 Soichiro Honda and his crew had built and were racing a four-cylinder 250 in Grand Prix competition, and winning. That little gem put out 46 horsepower at 14,000 rpm—just to show the world what could be done with a quarter of a liter.
On the CL72 engine power passed off the left end of the crank, a single-row chain going back to a wet multidisc clutch, the input shaft leading to a four-gear transmission. Nothing remarkable here, with the output shaft sprocket running a chain to the rear wheel.
On the CA/CB models the engine served as a stressed member of the frame, suspended from the steering head by two short arms that bolted to the cylinder heads. The main frame was a large round tube angling back from the steering head, then dropping down to behind the transmission, where the swingarm pivot was located. For the CL the R&D boys felt that more ruggedness was needed, as the bike was intended for boonie-bashing with lots of jumps and heavy landings. The two short arms attached to the cylinder heads were traded for a large single downtube which went down to a pair of tubes that cradled the engine, and on to the swingarm pivot. A sturdy skid plate was bolted on to protect the engine.
One retro aspect of the CL is that it had no electric starter, as the new downtube occupied the space that the starter took on the Dream and the Hawk. No matter, as kickstarting a two-cylinder 250 could be done by a small child or an arthritic grandfather.
The fork and shock absorbers had adequate travel, depending on the weight of rider (and passenger), and the shocks had three-position preload. A hydraulic steering damper was definitely a plus, better than the earlier friction units. Both wheels were 19-inchers, with a 3.00 tire on the front, 3.50 rear. Drum brakes used single-leading shoes on the front and the rear.
The saddle was standard flat, but not too terribly long; a passenger would have to be the friendly type. Under the seat were the battery and the air filters for the carbs. Fold the starter out, pull out the choke if it is cold, pull in clutch and clear the plates with one kick (that’s an old British tradition, but still valid), and let out the clutch. Now turn the key, and a kick or two would have this 15-incher (250cc) bubbling away.
Click the gear lever down for first, and accelerate away. The torque maxed out at about 7,500 rpm, although around town shifting at 5,000 rpm was the norm. On the pavement cruising speeds of 65 mph were fine. And then came the turn onto the dirt road leading into a state forest. Smooth dirt was fine, the mildly knobby tires giving reasonable purchase. But a trip down a long-unused logging trail could give a different impression, with limited grip and a suspension that was, well, barely adequate. After a couple of whoop-de-dos the rider would sensibly slow down. No problem; this was essentially a street bike with some pretensions at being OK on asphaltless surfaces, and purchasers understood this.
But bigger, in the American mind, is always better, and in 1965 the CL72 250 gave way to the new CL77 305, which size increase had been easily achieved by boring out the cylinders 4 millimeters. And it received constant-velocity** 26mm Keihin carbs. It was obvious that the land of the rising sun was not going to build just tiddler motorcycles.
**Don’t know where I got that “constant-velocity” line from. The carbs on the CL77 were 26mm Keihins, and the CL72’s were 22mm Biliaths. Clement Salvadori