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These were 6-port motors and featured CDI ignition. In 1971 Polaris built a 439cc triple in addition to their 649cc and 795cc motors. The sound was incredible from the triple pipes! The tradeoff was less torque (bottom end) with the shorter stroke motor. The over-square triples (bore diameter larger than stroke length) could now rev higher and that typically meant more peak HP. The 645 featured a 67mm bore putting out 71 hp and the big 797 was a punched out version with a 74.5mm bore putting out 88 hp. The Rotax triples used a short stroke 61mm crank. The ‘71 Blizzard had these big triples sitting right there in your lap with the motor mounted on top of the tunnel. the 15” track used on the twin-cylinder versions. The new Ski-doo triple-cylinder Blizzards were built on a wider tunnel using a 16.5” wide track vs. The 1971 season would see the manufactures expand their three-cylinder engine offerings. 1971 Ski-Doo Blizzard 797cc Triple cylinder
1996 POLARIS INDY 440 LIQUID COOLED FREE
The horsepower war was ramping up and to compete with the “Honker” motors Rotax would up the anti in 1971 with new free air 645 and 797cc triple/triples. Ski-doo had a successful season in 1970 but the writing was on the wall. Ski-doo introduced their new Blizzard race sleds in 1970 with 636 and 776cc twins. The 647cc produced rpm and the 793cc was rated at 82 hp rpm. For 1970 Arctic Cat, among other manufactures, would use the new Hirth “ Honker” free air triples. Kawasaki had already released their three-cylinder free air street bikes which were real fast and Arctic Cat wanted that power in their race sleds. Arctic Cat was just beginning to develop an alliance with Kawasaki, which was chomping at the bit to enter the snowmobile market. Polaris would race their new 649 and 795cc free air triples combined with their new aluminum flyweight clutch to many race victories. That would change for the 1970 season when Polaris introduced their “Star” engine built exclusively for Polaris by Fuji Heavy Industries (Subaru). The majority of engine suppliers at the time were primarily European (Hirth, JLO, Sachs, Kohler and Rotax). The limit was set at 800cc entering the 1969 race season. The horsepower race was getting out of hand, it was concluded (sound familiar?). The summer of 1968 at the annual USSA (United States Snowmobile Association) rules meetings had on the top of the agenda a call to put a limit on engine size. On the race track the hp race was escalating when the 634cc and 744cc twin-cylinder race sleds emerged. The birth of the twin cylinder 340,400 and 440cc engines soon followed for production snowmobiles. More power meant more cylinders and larger displacement. People bought a single-cylinder 12hp sled and once they became more comfortable with riding a machine in the snow they typically opted for a sled with more power. Everyone in the snow belt was buying one or seriously thinking about it. The popularity and growth of snowmobiling in the late 60’s was akin to the smart phone of today. The demise of the triple-cylinder two-stroke continues to puzzle for many of us and this story will look at the origins right through to the end when a host of changes in the snowmobile business silenced what many call “The National Anthem of Snowmobiling”.
1996 POLARIS INDY 440 LIQUID COOLED SERIES
The advantages of a three-cylinder engine are still utilized in many of today’s four stroke engines, including the most powerful production sleds ever produced in the Yamaha Sidewidner and Arctic Cat’s latest 9000- Series models, including the all-new Thundercat. It has now been more than 10 years since a two-stroke triple has been crated at the end of an assembly line. Memories of sleds like the SRX, Mach Z, XCR 800 and ZRT should make us all smile.īy the late 90s, big-bore twin engines like the Rotax 670 and Polaris 700 were rising in popularity and by 2006 the triple party had ended, seemingly rather suddenly, much to the dismay of many. For many snowmobilers there is no better sound on the planet than that of a triple-piped three-cylinder two-stroke engine singing at high rpm levels.
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The 120-degree firing sequence of a triple is sexy and very addictive. For several decades the ultimate high performance snowmobile was powered by a three-cylinder two-stroke engine.