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Free-Air Snowmobiles
    Friends ask me sometimes, "I've found this really cool (insert sled name) free-air for (insert price). Should I get it?" If you find yourself wondering this very question, or just want to know something about free-air (F/A) sleds, this is the article for you. Free-air cooling began in snowmobiles used for racing during the early 70's. Manufacturers realized that by casting bigger fins onto the heads and cylinders of the engine, and then placing the engine in the airstream moving by the sled, acceptable cooling could be accomplished. The cooling was more even then with fan cooled engines, which tended to run hotter on the cylinder farthest away from the fan, and weighed less than a fan cooled setup. It also didn't waste horsepower turning the cooling fan (or risk throwing the belt). Because of these advantages, the free-air design survived until the late 70's, when liquid cooling finally took over.  Although the F/A setup does have adavantages, like everything else, it has disadvantages as well. Free-air sleds are generally designed to stay moving. In racing, where the design was first used, this is not a problem. In fast trail riding (like on railroad beds), this is not a problem. But if you're puttering around the yard, and it's a warmer day, sometimes you can run into overheating problems, especially if you sled's tuning is off. Of course, in what conditions this happens varies from sled to sled, but it is something to be aware of.  Free air sleds also tend to be slightly more tempermental then their fan cooled cousins, mostly because of the higher state of tune that the engines are in. All in all, free-airs are best left to the more experienced vintage collector/rider. That's not to say that if you happen to find a 75' F/A T'nT 245RV in perfect shape for $50 and you are new to vintage snowmobiles you shouldn't get it, but on that same note, perhaps it shouldn't be your first sled choice.



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©2003 Stephen Phillips, Stib Inc.
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