Free Air Ski-Doo's
An 
Unofficial History
In the early 1960's the sport of snowmobiling was at the beginning of a decade of incredible growth. One of the big challenges facing these pioneering companies was that of finding engines in suitable numbers to meet the growing consumer demand for their little snow travellers. The first engines used by Bombardier were small air-cooled industrial four-strokes produced by Kohler and while the four-strokes were easy to obtain, their use in winter operation was marginal at best.
The low-weight, high-power output and excellent low-temperature starting ability of two strokes quickly made them the engine of choice, and a 247 two-stroke pump engine from JLO was used in 1961. In 1963, Armand Bombardier entered into a with a deal with the Austrian engine manufacturer Rotax which gave him the exclusive rights to the small two strokes that Rotax was supplying into pumps and generators, The first Rotax powered Ski-Doo's were born!
1976 T’NT 250 RV
Engine Cooling
These early air-cooled engines were all fan-cooled. Their single or twin cylinders were cooled by either a centrifugal-flow, flywheel mounted fan or a belt driven axial flow fan.
Axial-Fan Cooled 1968 Rotax 600
In
the racing boom of the early 70's, the quest for speed led engine builders away
from fan cooling to a cooling system that relied on outside air flowing over
and through the moving snowmobile. Outside air was ducted into the engine
compartment through large openings cut in the hood and directed to oversized
cooling fins cast into the cylinders and heads.
This method of engine cooling, referred to as free-air cooling, was dominant in the racing and high performance sport sled markets until the advantages of liquid cooling were fully realized in the late seventies. Free-air cooled sleds have characteristically large openings in the hood, and the engine may even project from a lowered hood profile.
1972 Free-Air Cooled 400
Eliminating the cooling fan of an engine resulted in many performance benefits. First, the power required to drive the fan was wasted and could be better utilized propelling the sled. This could mean as much as a 4 hp increase in a 50 hp engine. Fan cooling of multi-cylinder engines often resulted in the cylinder farthest away from the fan running hotter than its partner. This uneven cooling problem would be even worse in the three cylinder engines that were being designed during this time. Finally the weight of a fan, it's drive system and shrouding added weight to the motor and ultimately the sled. Every major sled manufacturer in the early to mid 70's produced free-air cooled racing and sport-performance trail sleds.
About This Site
The following web pages present the unofficial history of Bombardier's Rotax-powered free-air cooled Ski-Doo's. Included is information on production race sleds, consumer sleds, one-off factory built prototype racers and speed machines. I've organized these pages by the model years in which free-air sleds were produced, 1970 to 1978. The model year 1970 for example referring to machines manufactured in the fall of 1969 and ridden in the winter of 1969-1970.
In each section, I have attempted to present the highlights of each machine, both technical and historic. Each sled is rated for its "collect ability" using a very subjective five * scale based on the sleds impact on the sport and its rarity. Technical notes of interest to the owners and restorers of these great snowmobiles are presented, along with information for obtaining parts in the restoration section. I have also accumulated a specifications section, which might prove handy if you're trying to identify a hulk under a hay pile some day.
As the page matures, I hope to pass on rider impressions from the people that rode and raced the machines. To that end, I hope that readers of this page that have some information to share will forward it to me so other enthusiasts can enjoy it. I have attempted to make these pages as correct as I can, if there are any errors or omissions, please let me know so they can be fixed. There's also a bibliography page that lists the published sources from which I have used as references for this history.
Finally, to all you old time sledders. How about putting together a page of your own? I know during the heydays of the sport there were some significant sleds from the other manufacturers. How about a GPX page, or an El Tigre page or a TX page?
Enough introduction already.....
1971|1972|1973|1974|1975|1976|1977|1978
|Restoration|Specifications|Bibliography and Links|Wallpaper
E-Mail to Doug Hakala: Comments, questions, additions to this page will be gratefully accepted
In 1998, the very nice people at the Vintage Snowmobile Club of America awarded this site their first ever Golden Sled award.
In October of 1999, SnowRider Magazine awarded this site their Web Page Award.
This site is dedicated to the memory of
Arto Viik, a good friend, a great team owner, an avid outdoorsman and someone
who played a big part in my brief racing career. He was gone too soon.
NOTE: The information presented here is for the use and enjoyment of the snowmobiling public and is not intended to generate a profit in any way. The author will not be held responsible for the accuracy of the information. Ski-Doo, Sea-Doo, Rotax, T'NT, Blizzard,Olympic,Elan, Torque Reaction and the Bombardier Logo are all registered trademarks for Bombardier Incorporated and are used without permission.
Last Updated: May 6, 2002