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While I was sitting in flight theory class, the instructor was talking about carb icing for the planes that we fly. See, as the high speed air air passes through the venturi in the carb and picks up the vaporized gas molecules, the temperatures can drastically decrease. When we fly these little airplanes on cold days, we have to use what is called "carb heat". All it is, is a airbox or farings that directs air over the exhause pipes, "which heats up the air" and then forces it into the carb. This melts any ice that was forming inside the venturi of the carb and eventually makes the engine run better. Now that I explained this, why haven't I ever heard of this on snowmobiles? People way up north in the really cold areas, I would think would have problems with carb ice forming. On the brand new airplanes that have electronic fuel injection, there is no longer need for carb heat because since there is no carb for the fuel to be mixed in, the temp. cannot decrease to form ice. This is just another one of my day-dreams that helps me through the 3 hour class, 2 times a week. Let me know what ya'all think on why snowmobiles do not need carb heat?

Wanted!! Polaris 340 TXL any Polaris 340 or TXL. "[email protected]"
 

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Well, your right. Some snowmobiles do have a coolant line going through the carbs that keeps them from freezing up. If i remember right, some Yamaha tripples have that. My Polaris twin doesn't, but i don't think it needs it either, unless there is alot of snow being ingested. And as long as you have an airbox and foam filter, everything should be fine.

Let it snow!
 

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Yes, my 99 MM700 triple has a liquid heating system for the carbs. My XLT on the other hand does not. My brother was riding his this weekend, 5th in a line of 5 sleds and he was subject to some carb icing. In fact the slides stuck open at about 5K rpm and we had to come to a stop for a while and let the motor warm up the carbs so the slides would move freely again. That sled has the airbox and foam pre filter too. It can still happen. Remember though 18scott that when you pull carb heat on in a plane it will clear the icing condition but you do rob the engine of some HP while you have it on. Engines do not like warm air in the intake. Easy enough to say when you're on the ground anyway.

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I think.... therefore I sled
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Two '94 Indy XLT SKS

Edited by - Bman on November 28 2001 2:26:13 PM
 

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My viper has heated carbs.....the dealer said to only turn them or when its really cold or there lots of snowdust and conditions like that
 

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Yamanator do you know which direction to turn the valve so heat is going to the carb? I don't have a manual for my MM. thx. It can twist 90 deg and point either toward the carbs or toward the outside of the sled. Thx.

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I think.... therefore I sled
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Two '94 Indy XLT SKS
 

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The carbs on my xlt froze up a few different times last year. They would stick open and then the cable would come loose from the hand throttle. I hated it. This only happened when there was lots of fresh powder snow though. The idea of the carb heater is a neat one though

 

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Perfect, thanks dude!

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I think.... therefore I sled
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Two '94 Indy XLT SKS
 

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18 scott
It is a novelty thing to have sled carbs heated. It can be usefull in alot of situations but for the most part not a neccesity.
The small aircraft have a carb-heat feature for a specific reason. The most common reason is even on a nice day the temp at 2k is going to be cool. So if you take off at 45deg day and climb hard to 3k the temp is likely to be frigid. The most common time for carb ice is takeoff climb. This is a full throttle situation and thus the most drop in temp at the venturi. (note aircraft carbs are not slideing vein type except on ultralights) You now take a fairly warm carb from run up and make it cold fast, you are going to get condensation. Ta dah! carb ice at a bad bad time. You can also experience ice at altitude if there is moisture, noted by a loss of RPM. So that is why you NEED a heater on a naturaly asperated engine at altitude and take off. It is real hard to just pull over and let it melt a little before going again. You normally do not run the carb-heat durring flight it makes the engine less efficient.

"Meaningless Ride"
 
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