In the early ’60s the Big Bear race was a pretty serious event, running across California’s Mojave Desert and up to Big Bear Lake in the San Bernardino Mountains. The idea that this beautiful, highly chromed street-scrambler had any possibility of winning against high-strung Euro-bikes like Maico, DKW, Jawa, etc., was a pipe dream. However, Yamaha decided to appropriate the prestige of the name in 1965, without ever having won the race, by calling its YD 250 street-scrambler a Big Bear.
For the ’67 model year it confused the issue even further by also giving its new YM2 305 street-scrambler the same name. This turned out to be a one-year-only model, sold only in the United States, some 6,000 units passing through the dealers.
The parallel-twin, port-timed two-stroke came with a compression ratio of 7.2 to 1, and the factory was claiming an output of over 30 horsepower at 7,000 rpm. The cylinders were bored to 60mm, stroked to 54mm, and fed by a pair of 24mm Mikunis. In turn, these were sucking in a mixture arranged by Yamaha’s Autolube oil injection system, with the oil being introduced into the intake ports, rather than injected into the crankcase. Yamaha was the first two-stroke manufacturer to simplify life for the rider with the Autolube system—Suzuki and Kawasaki were quick to follow. Since the amount of oil injected varied according to engine speed, at full throttle the mixture was maybe 20:1, at idle, 200:1.
On this model Yamaha had made a major change in the drivetrain—previous YD 250s and YM1 305s had the clutch mounted on the left end of the crankshaft, but on the YM2 it had been moved back to the transmission shaft. Crankshaft clutches have several dubious qualities. First, it makes the engine wide, which might not be helpful when coping with fast corners. Two, it is harder to balance the whole engine with that heavy weight on one end. Though on the YD at the other end a rather bulbous cover housed the less weighty alternator and ignition points, giving whomever was fiddling with the ignition easy access. Third, such a design—with the clutch running at engine speed rather than reduced as it would be on the transmission shaft—makes the clutch grabbier since there is little possibility of putting any cushioning in there. It is now accepted wisdom that it is better to have the clutch at the transmission end of the primary case.
The gearbox had five ratios, and since the input was on the left side, the output to the rear wheel on the right, it made for better balancing. The kickstarter was on the left side, but fortunately that was infrequently used, thanks to the electric starter.
A bit of history. When Frank Cooper took on the job of distributing Yamaha motorcycles in the United States in 1960, he knew that some changes would have to be made —especially in the naming. When the Japanese company first began selling its own motorcycles in Japan in 1955, the YA1 was the focus. It was a nice little 125cc two-stroke single, but the alphanumerics were a bit of a yawn-maker. Then came the 175cc YC1 in 1956, followed by the YD1 250 a year later. While the home-market was happy with this identifying process, Cooper knew that Americans wanted a little more drama.
When he put a half-page ad for his 250 line in the August 1960 Cycle magazine, he called one the Grand Prix Sports, the off-road/lightless model the Grand Prix Scrambler, and the one with electric starter the De Luxe Twin. Then the Japanese suits took over and reverted to the old system of identification, promoting the YD3, with electric starting, and YDS2, the sporting version. But it was the introduction of the TD1 (no idea where the T came from) 250 roadracer which actually put the company on the racing map, but that is another story. Yamaha was soon thinking about upping the engine size to 305 to meet its main competitor, Honda, which had been very successful with the 305 Super Hawk.
The 250 YDS3C Big Bear came on the scene in 1965, but it was a scrambler in name only. A little bit of dirt-roading, perhaps, but that would be the limit of its scrambling ability. Street-scramblers were one of the motorcycling styling vogues in the mid-’60s, and nobody had any illusions about their intentions—paved roads.
Move forward 18 months and the YM2C 305cc Big Bear was introduced, and soon arrived at the dealers. Who had a hard time keeping them in stock, not because the buyers thought they could win the Big Bear race, but because the bike looked so darned cool. There was chrome everywhere, on the gas tank, the fenders and the two big upswept exhaust systems. Along with open chromed springs on the fork and shocks—the shocks here are not original, but are similar ones from Redwing. And, of course, a bit of bright blue—or red or black, the other colors available.
The engine was bolted into a full-cradle frame, with preload-adjustable shocks at the back, a standard hydraulic fork up front. A hydraulic steering damper was mounted on the fork, an indication of the bike’s intentions—off-road riders like friction dampers, not the hydraulic type. Eighteen-inch wheels used a 3.00 Dunlop Universal tire and single-leading-shoe brake at the front, 3.50 and another single-leading-shoe at the back.
This was no lightweight. With four gallons of regular in the gas tank and four pints of oil in the Autolube tank the Big Bear 305 weighed in at over 360 pounds, with the wheelbase a tidy 51 inches. Top speed was in the 80s, but riders weren’t very interested in that—too fast to be admired. Big Bear types preferred idling around town, or the campus, and let the onlookers be envious. In truth it was a perfectly adequate street bike, with those never-used off-road pretensions. And it only cost $700.
Then, several changes came in the Yamaha line-up. First, the apparent successor to the 305 Big Bear was the 350cc YR2C Grand Prix Scrambler, introduced in December of 1967 with an extra hundred bucks on the price tag and an extra 5 horsepower at the crankshaft. Second, the brilliant new DT1 250cc single-cylinder enduro machine was introduced, offering genuine off-roadability and forever changing the notion of dual-purpose motorcycle.