Making A Snowmobile Engine Run In Warm Air


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Old 12-22-10, 09:47 AM
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Question Making A Snowmobile Engine Run In Warm Air

Other than not running to lean a mixture and getting plenty of air, is there anything else that has to be done to the engine of my 96 rotax 670 that has a big bore kit in it, and is something like an 800 now. Would it be necessary to run a large fan like a sand rail would? I know its a large motor, but it will be a decent size frame with two seats. An overgrown go-cart, but not quite a sand rail.
 
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Old 12-22-10, 09:53 AM
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Exclamation

Also if anyone has any pictures of snowmobile to go-cart conversions, especially the drive train area that would be great!
 
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Old 01-01-11, 11:46 AM
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You probably would want to add some kind of cooling to it, since it is a snowmobile engine that is designed to run in below freezing conditions, so the normal running conditions for the engine act as cooling for the engine. Since the freezing conditions would be gone, the cooling would need to be replaced, even if it didn't, better be safe then sorry. If nothing else, you would get better performance from the engine.

With an engine that big, you would probably want to get an old axle from a small car, or a chain from a motorcycle. It is quite simple to modify the drivetrain once you have decided for a chain or whatever you are doing, since most engines usually have a axle with a slit in it to attach things to it, so if you carefully take off whatever is already there you should find a pretty universal connection underneath.
 
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Old 01-03-11, 05:48 PM
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The cold air is only a part of cooling for a snowmobile. Originally that machine used 2 very large heat exchangers under the seat as the track went around it threw snow up onto these exchangers cooling the coolant. Thats why if you run your machine hard on ice with no powder especially for long periods it may over heat. You will need to get a radiator and a fan large enough to handle the cooling
 
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Old 01-03-11, 06:10 PM
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With most liquid cooled snowmobiles air cooling has only a small effect on cooling. As Setlmashuck mentioned, snow is the larger part of the cooling with the heat exchangers in the tunnel and under the running boards. You will need to replace these with a heat exchanger and an electrically driven fan.
 
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Old 01-04-11, 03:36 PM
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Thank you very much for your input! I'll start looking for a radiator and a fan and go from there. Do I need to do any re-jetting, or just run my mixture a little richer and adjust the jets?
 
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Old 01-04-11, 05:49 PM
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You might also want to see what is done to the racing machines that are run in the spring and summer on dirt and grass in addition to water. It all started when people would try to skip across the water (just like snow skiers do) when the snow was melting and then just went from that.

dick
 
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Old 01-07-11, 02:42 PM
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Well, really you shouldn't need to do anything to the mixture. If it comes down to it, find the adjustment screws on the carburetor and fine tune it. To get a good adjustment you start the engine, bring it up to full trottle, and turn the screw tighter or looser until the engine isn't coughing or sputterring whilst running. Hope the project works out great!
 
 

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