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Triples vs. Twins

    If you go out and buy a sled these days, you are faced with several decisions to make: Do I get a short or a long track? Liquid or air cooled? Muscle, Cross Country, Hillclimb or Touring? Widetrack? Suspension?...etc...... However, one of the most common questions about getting a sled is the arguement, "Should I get a triple or a twin?". Hopefully this article will shed some light on the differences between the two (other than the number of cylinders) and the track record they both have thus far.
    The triple twin arguement dates way back in snowmobile history, back to the early seventies when the triples first started coming out. At the end of the Dark Ages, dominated by singles, manufacturers realized that power gains could be had by grafting on another cylinder, thereby producing a twin. Soon after that, they decided to try the trick again, and the triple was born. Unfortunately, although the twin had been a vast improvement in power, vibration, and overall smoothess, the triple seemed to exchange reliabilty for even more power. Thus the triple gained the reputation early on as being tempermental, rev happy, and prone to blow up. For all out power though, it was hard to beat. The 72' Blizzard 797 free air triple/triple produced 102hp, at a time when a 40hp sled was pretty hot. But, then again, the Blizzard was a race only sled, not intended for trail use. So the finicky nature of its 3cyl engine could be tolerated. So, if you're getting a vintage sled with a triple in it, your probably looking a machine that was meant for high performance use (there are exceptions), possibly racing, and will be a pain to maintain and run on a regular basis. (note: I run all of my sleds. If you want a trailer queen, than it really doesn't matter what you get because it will only run 5 min or so every year.)  Now, what about newer sleds? Well, as mentioned in other sections of this site, most of my knowledge concerns SkiDoo, so the engines refered to will be as such. However, if you have something that you'd like to add as far as other brands, please, email me. Anyway, with the newer sleds, and thus newer engines, most of the earlier gremlins that plagued triples have been eraticated for the most part. Sure, the engines themselves are more complex, along with extra carb and hosemongery that goes with it,  but that could be worth it depending on your needs. Or not. The problem that I've noticed with triples stems from three things: #1. From the mid 90's on (maybe before), Rotax triples seem to have a problem with eating one of the outside bearings, and then burning the adjacent cylinder as a result of the ensuing air leak. Although this doesn't seem to happen to everyone, and claims of 5000+ problem free miles on Formula III's, Mach 1's, and Mach Z's have been made, it seems that more people are complaining that they blew a crank at 700 or 1000 miles rather than 5000. Also the people that are making these claims of high milage usually say "skidoo oil (sythn or dino) is crap, run aftermarket, etc...". It seems to me that if you can't have reliabilty in a sled and run the manufacturer recommended oil, something is wrong. The other popular "fix" for the Rotax triples is to put a zerk fitting on the PTO (clutch side) bearing and pump it full of grease every so often. While this does work, apparently well, how come SkiDoo/Rotax didn't do it right in the first place and make the engine with the proper oil guides? Seems like a botched design to me. #2. While a few of the rotax snowmobile engines crossed over into the PWC world, no Rotax triples seemed to have been used in SeaDoos other than the new supercharged, 4 stroke triple. Engines run in a marine environment usually have a much rougher life, as well as higher operating temperatures, as indicated by the fact that marine 2 strokes always have a lower compression ratio then their snow-bound counterparts. Think about it, most PWCs are run at WOT, or close to it, while a snowmobile will spend a decent portion of its life running at part throttle, even if it's out on the trails going 70mph. I think the reason Rotax 2 stroke triples aren't found in SeaDoos is because they could get any of them to last in durability tests. (Please note: This last statement is just my opinion, not a fact) #3 This is an excerpt from a snowmobile comparison site:

    "Introducing the new monster of the 700cc class. This is an all-new Mach 1,
featuring an all-new, all-out 699cc Rotax triple with three VM38 carbs and
triple tuned pipes. Like all Rotax triples, this new engine features R.A.V.E.
exhaust port modifiers for peak performance throughout the rev range, plus
plenty of innovative technology that includes Nicasil cylinder linings for
less weight and better heat distribution, as well as a new intake resonator
that allows the engine to run leaner without overheating for more efficient
performance, and a new oil pump that halts delivery at idle speed, effectively
reducing emissions. But the Mach 1 is more than just an incredible engine.
It's a total performance package that includes our SC-10 High Performance rear
suspension with ACM, a new longer-travel DSA front suspension, new, more
aggressive handling plastic skis and a new short track with .912-inch (23.2mm)
lugs and a new track pattern for greater traction, better braking performance
and less weight. The list goes on with new sliding hood grilles, new high-
visibility whiteface gauges and the comfort of a seat with fabric that
stretches all four ways. Check out the new Mach 1, a sled that makes no
apologies and takes no prisoners."


It seems to me that if an engine recieves no oil at idle, and is at idle for an extended period of time (ie warming up when it's -30 F) , engine damage (ie bearings, etc..) could definately take place. You be the judge.


None Yet.

©2003 Stephen Phillips, Stib Inc.
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is the opinion of the owner.