1975 TNT 245 RV – Black is Beautiful

In the winter of 1975 if you wanted to know what was coming down the pipe from your favorite sled builder, the race fan was heading to the oval track to have a look at the SnoPro oval race sleds or the limited build oval stockers.

The winter of ’74 had been tough on the Ski-Doo faithful. Bombardier had pulled the plug on its involvement with the SnoPro race circuit. The reason? An oil embargo had grown into an energy shortage and negative attitudes among none and anti snowmobilers was growing. How could people justify burning gas in a snowmobile when they were lining up for hours to fill their cars or having a hard time getting fuel oil to heat their homes? Bombardier used their factory riders (Yvon DuHamel and Mike Trapp) as good will ambassadors to promote snowmobiling instead of racing around oval tracks.

The task of winning checkered flags was left to the privateers competing in the 340 and 440 stock classes aboard the T’NT Free Air. The chassis, which had dominated the 400 class in ’73, was starting to show its age in ’74. The Mercury Sno-Twister, Arctic Cat Z and Yamaha GPX provided stiff competition.

Back home in Valcourt, Quebec, Jean Guy Talbot and Sam Lapointe were leading a group designing a new snowmobile that was to introduce many firsts on a production Ski-Doo snowmobile. The sled introduced to the press in November 74 was called the T’NT F/A 245RV. The name was the same but the features hidden under what many call the best-looking Ski-Doo ever built were numerous. Ski-Doo built the RV to compete in the 250 class dominated by Arctic Cat. At the end of the 74/75 season, Ski-Doo had claimed the 250 Stock and Mod Stock titles at the USSA World Series in Weedsport, New York. Jean Guy Talbot had done his homework very well.

The 1975, T’NT F/A 245 RV project began in 1973. The Sno-Jet Thunderjet had demonstrated that a wide ski stance and low cg could translate into faster speeds in the corners. The new sled was built around a 34” ski stance using lightweight aluminum alloys to construct the chassis. The engine was positioned in the center of the chassis and not offset. Jean Guy Talbot explained, “The RV was designed initially to be raced on the oval track, but we also knew that to make the machine better balanced the weight should be centralized” Sound familiar? To keep the weight down, the belly pan was all fiberglass and featured sexy side bulges that enclosed the aluminum front cross member.

Total sled weight was (a scant) 320 pounds. The RV was distinguished by a flat, squared off black hood with an orange inlet scoop that directed air into the engine. The black color was a huge departure for Ski-Doo and signified a change in direction; not just in color, but in execution. Perhaps the color black was chosen to “get in Cat’s face”.

The RV also was the first production Ski-Doo with a rotary valve engine. The 247-cc motor was the first of many rotary valve engines that would be used by Ski-doo for more than 25 years. The RV motor also came with Mikuni VM34 carbs, which was another first for Ski-Doo. Previous to this sled, all production sleds were sold with Tillotson carburetors. The 247 RV motor put out 43 hp @ 7900 rpm, which was comparable to many 340cc piston port engines of the day.

To transfer that power, the RV featured a new square shaft primary clutch. The “Instant Torque “primary introduced a year earlier featured a low ratio of 4.5:1 which was quite different from “standard” high performance clutches of the day which had 4:1 starting ratios. The clutch was not great at downshifting and this hampered the RV when the throttle was let up going into a corner.
The secondary clutch was mounted directly to the chaincase which was “old technology’ on race sleds of the day. Phil Mickelson who was the service manager for Bombardier in the 70’s explained the reasoning; “The chaincase mounted secondary saves weight over the jackshaft arrangement and moves the secondary clutch into the center of the chassis to centralize mass. In addition the RV featured a magnesium chaincase cover to reduce weight and with no muffler located on the left side of the sled, gearing changes were easier to do.”

The other unique feature of the RV was it came with a steel cleated rubber track. No production Ski-Doo before or since came with this type of track which was common to Arctic Cat and Polaris sleds of the day.

The RV track was unique because it was the first internal or involute drive track used on a Ski-doo production sled. Most cleated track designs of the day used a front drive axle that engaged the cleats. The involute design improved efficiency and was lighter. The front drive axle was aluminum, which reduced rotating weight, all of which improves throttle response.

The 105” long track worked well on the racetrack, but for a consumer lucky enough to get their hands on one of these machines, it meant less flotation, and a sled that did not offer the smoothest, most stable ride. In fact as the RV chassis evolved into the cross-country RV, the chassis was lengthened and a longer track was installed to improve ride and stability.

The 245 RV was a sled that looked as good as it delivered. It gave Bombardier a much-needed home run on the ice ovals after a year’s absence and forced the competition to go back to the drawing board if they were to compete in the 250 stock class in 1976. Ironically, Ski-doo did not produce an oval track special RV the following year, but chose to take the 75 chassis and make it more suited for trail use. The consumer was the big winner with this move, but the race fan suffered.

In retrospect, the RV chassis of Jean Guy Talbot would enjoy more success on the cross-country circuit than it did on the ovals. Gerard Karpik (inventor of the M10 and Blade snowmobiles) was unbeatable for two years running on the pro cross-country race circuit. Ultimately the RV chassis demise came with the advent of independent front suspension. The evolution of the RV chassis was complete, but the technology introduced under the hood gave real meaning to the saying “Beauty is more than skin deep”.

By Hal Armstrong – SnowTech Canada

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