Can-Am 250TNT Enduro
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COLOR PHOTOGRAPHY: LARRY WILLETT • The degree of proficiency attained de Can-Am’s history is brief and impres and build a complete line of street and termines the sophistication of the tools sive. It begins with Bombardier Ltd., a dirt motorcycles for Bombardier. Robison required. A housewife needs only an add company headquartered in Valcourt. was a Californian who learned about mo ing machine for balancing her check Quebec and founded in 1937 by Joseph- torcycles by tuning race bikes and grinding book. but a launch expert must have a Armand Bombardier to build snow cams for Harmon & Collins. The Bom complete computer to calculate rocket vehicles. Today, after rocketing into the bardier Directors gave him a white sheet trajectories or balance differential equa economic stratosphere with the sale of of paper and unlimited funds and said, tions. The Can-Am is the computer of more than 1 million Ski-Doo Snowmo “report to us once a month on your prog off-road motorcycles. It’s not for everyone, biles since 1960. Bombardier controls 20 ress. And by the way. add the profitability because its high powerband makes it other concerns and markets motorcycles, of the motorcycle division to your list of harder to ride than a Yamaha Enduro. snow vehicles, tractors, plastics, apparel responsibilities.” But the same powerband in the hands of and rubber goods in 32 countries through Robison formed a design team (which a motorcycle launch expert makes the 4000 dealers. Sales last year totaled presently numbers 65) in the motorcycle Can-Am the best enduro bike in the $156,000,000. R & D department, and attributes world, regardless of displacement. In 1970 the company determined that Can-Am's success to his entire staff. The magnitude of such a statement is motorcycles would (1) provide needed Others in the company say it couldn't have enormous considering the existence of diversification. (2) furnish a second major happened without him. Penton and Maico enduros, but Cycle is product line for some 2500 snowmobile One of Bombardier’s major wholly- convinced the Can-Am is No. 1 (in spite dealers and (3) allow full utilization of owned subsidiaries is Rotax, an Austrian of several shortcomings) simply because assembly lines normally idle during the engine-building firm with elaborate two- its performance numbers and other strong off-season. The Board of Directors hired stroke production facilities. During 1971 points are so overwhelming. an American, Gary Robison, to design Robison flew to Austria 15 times to super- If you get tired of trails, you can win a motocross without even removing the lights. If you tire of moto cross you can win the stock 250 street class at the drag strip—knobby tires and all. After that you can do some cafe racing, and win your share again. If you get tired of riding, you can win some money instead. Just make a few bets with your friends about horsepower. 28 CYCLE mm**-- vise the design and testing of Can-Am’s the Yamaha, Kawasaki or Suzuki street in an enduro without constant shifting, but incredible rotary-valve engine. Most of the 250 Twins can threaten that figure. The such high hp figures naturally steal torque following year was spent on chassis work enduro bike most similar to the Can-Am from the low end. Since it’s impossible and prototype production. Late in 1973 in concept and performance is Penton’s to have both, Robison has opted for the Bombardier released four Can-Am mo 250, which ran 1.4 seconds and 9.02 mph screaming meemies. “Without a reputa torcycles to the public—a 125 MX, 125 slower. tion or established dealer network to sell TNT Enduro, 175 MX and 175 TNT On the dynamometer the Canadian motorcycles, Can-Am must sell horse Enduro. All four bikes immediately bombshell exploded for 27.73 horsepower, power,” says Robison. “Either you build proved their worth, but easily the most an amount any manufacturer would be it for serious riders or you build it for impressive competition achievement was happy to find in their motocrossers and the Sunday cow-trailers. The Japanese Billy Uhl’s tie with Carl Cranke (250 Pen- an amount which exceeded the Penton’s have the Sunday bunch well-covered, so ton) and Jack Penton (400 Penton) for the best by 1.17 hp. During a flash reading we build for the pro. A good rider can ISDT Qualifier series championship while in which the Can-Am was revved directly go faster with lots of horsepower than he riding a 175 Can-Am Enduro. He was also to its 8000 rpm power peak, output can with lots of low end.” the only rider in the series to win a Gold reached an astounding 30.03 hp. So seems to be the case in the real Medal in all six events. Out in the field these enormous perfor world. Pentons have even more radical Similar feats of giant-killing were pre mance figures suggest that the Can-Am power characteristics than the Can-Am, ordained for the 250 by its performance should be able to set fast time in any Six and of the 30 men who qualified for this numbers. At Irwindale Raceway Cycle’s Day special test section, and threaten even year’s ISDT, 14 rode Pentons—making Can-Am walloped every other 250 we 400 Huskies in high-speed cross-country them the cross-country bike to beat in have ever drag tested with a 15.040-sec- events such as Baja. There is enough mid America. When going fast really counts, ond, 85.22-mph quarter-mile. Not even range power to bounce along at 24 mph America’s top riders prefer the acceler- RHOTOGRAPHY: DALE BOLLER, BILL DELANEY Bold tank striping and a stubby cylinder give the Can-Am a distinctive look. The number plate implies its purpose—enduros and ISDT qualifiers. Coefficient of expansion of plastic insert equalizes Symmetrical head requires a 30 thousandth squish Porting couldn 7 be simpler. Two bridged transfers expansion rates of bearing and case. band and features enormous finning. and a huge exhaust accent the rotary valve. 30 CYCLE ation and top speeds provided by sheer torcycle engines before it. Enthusiasts de studs have to be removed to get the cylin horsepower. These riders, and several signed it. It took shape on a drawing board der off while the engine is in the frame. thousand others across the country, are with space-age technology and materials Massive finning on both the head and skillful enough to maintain the ground at its disposal. cylinder dissipate heat fast. Even at peak speeds which keep a high-output engine But ideal circumstances don’t make horsepower on the dyno, temperatures in its powerband, to manipulate the throt horsepower. Metallurgy, rod-length-to- hovered at the safe 400-degree level. Once tle accurately enough to avoid wheelspin, stroke ratio, port timing, quality control while prerunning the Baja 500 course in and to shift as required in the midst of and other basics do. Bombardier uses rad Mexico, mud covered the engine; it still any kind of terrain. A novice may be ically over-square bore and stroke (74 x didn’t ping or detonate from over-heating. intimidated by such demands, and more 57.5mm) dimensions along with hot port In addition the engine refused to cough experienced riders simply may not like timing and a large chunk out of the rotary or lose power at altitudes from sea level such power delivery characteristics. For valve to achieve power. The cylinder and to 5000 feet even while running on oily them, and the novice, an Ossa or Yamaha head on the enduro is the same as the low-test Mexican gas. with lots of bottom-end torque will be motocrosser, yet it idles without a fuss and Inside the engine, a Dykes top ring and easire to ride, and therefore preferable. persists in starting on the first kick. Porting standard second ring for oil control en But for guys who can use it, raw horse consists of two bridged transfers, a huge circle a cast aluminum piston. The rod power is the quickest way down a trail. exhaust and an egg-shaped intake port carries needle bearings top and bottom. The engine responsible for this power opened and closed by a thin steel rotary Nothing reflects the Can-Am’s space age was built under ideal conditions: unfet valve geared to the crankshaft. The holes genesis more than the special plastic liners tered by previous design restrictions, ex in Bombardier’s steel liner match the ports which support the huge ball bearing isting production facilities or lean budgets. in the beautifully die-cast cylinder exactly. mains. The coefficient of expansion of the It benefited from all the mistakes in mo Our only complaint is that four cylinder plastic is equal to the difference in expan- Unique ram tube locates the carburetor rearward for less engine width A bell-shaped velocity stack is moulded into the carburetor air box boot. and contributes greatly to superior breathing. The rugged clutch runs wet. Three different chain shrouds are available to match different sprockets. Removing the ram tube reveals a giant rotary valve and the intake port. Drum and fork mechanism provides faultless shifting. Removeable bearing retainer plate on transmission shafts eases shimming. Idler gears spin on needles, shafts on balls. OCTOBER 1974 31 50 50 - - Engine - - Speed BHP Torque - - 3000 5.66 9.92 “ 3500 7.00 10.50 4000 8.06 10.58 .