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Thread: Retrofit carb heat?

  1. #1
    Member akjw7's Avatar
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    Question Retrofit carb heat?

    Had some bad carb icing really for the first time this past weekend.

    Anyone every tried to come up with a cheap easy way to add carb heat to a sled where it wasn't an option? (liquid cooled)

    buying carbs for a sled that did have carb heat is not an option...to expensive and no creativity!

    Here's my thought -

    get a couple thumb warmers and attach them to the carb body - say right below the throttle slide/cable nut on top. Wire them up to a small out of the way switch and there you go - carb heat.

    The thumb warmer on my machine gets plenty hot (too hot for a gloved thumb if it's on high for very long) and the aluminum carb should transfer heat well. I think it could work but, it seems almost too easy, so I'm wondering what am I missing - can it be that simple?

    Only problem I see is finding enough of a flat surface to relaly get the thumb warmer adhered well to the carb body - zip ties might help...or just wrap it in duct tape!

    Another idea someone threw out was to wrap a coil of small flexible tubing (vinyl perhaps) around the carb bodies several times, then tap it into supply and return points in the cooling system with a shut off valve. When you turn the valve to open warm coolant circulates through and warms the carb.

    Seems like another workable solution, but at first glance it doesn't seem like a very clean mod compared to the electric option.

  2. #2
    Member Dupont Spinner's Avatar
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    The most likely cause of carb icing is the ingestion of snow. Make sure your boots and intakes are sealed well. At the opening cover with snow filter material.

    http://www.slp.cc/catalog.cfm?pageID...&productID=413

    This can be cut to size and hot glued in place.

    What sled????

  3. #3
    Member akjw7's Avatar
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    old summit 500 rotax, it does have a couple screens in the intake system.

    boots were sealed up good and I looked for some obvious ingestion signs, but couldn't tell anything obvious. Carbs were very frosty...like a 1lb propane bottle used in the winter!

    Also it happened before we got into the any depth of snow - rode a trail a mile or two with lots of on and off the throttle, then we hit a lake where it was more steady throttle and wide open at times - that's where it iced up. Repeatedly.

    After about three times of getting it cleared it seemed ok and we went into the swamps to play - no problem after that.

  4. #4
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    you could tap off the coolant line and run a coil around the carbs, my Rev 800 has carbs that run coolant thru them to keep them warm, it also has a valve so you can shut the coolant out during warm spring riding days

  5. #5
    Member matjpow's Avatar
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    Now take into account I am using my aviation experience. Carb icing (due to condensation) generally only occures when temps are right at or just above freezing. Even in the winter it is possible the the engine compartment is hovering right at 33F and water vapor is getting into your intake. Carb heat will reduce your horsepower so you only want it running when you are in icing conditions. I think the thumbwarmer would be a better idea because you could reach high temps fast and turn it off after the ice has cleared (only problem I see here is the possiblility of vapor lock if you heat up the fuel.) A homemade coolant line could be problematic because you might heat the carb up just enough to make the icing worse. Also you might run into problems with leaks and what-not with your coolant system.

    If your machine has a factory coolant heated or aftermarket heated carb then that's fine but if it has a shutoff valve then you might want to think about shutting it off if you want to get a little more horsepower out of it. Panzer, warmer temps (around 33F) would be when you want to use carb heat because water vapor entering your carb freezes due to the lower atmospheric pressure in the intake system.
    That's what she said...

  6. #6

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    Snow ingestion or water in fuel along with just the right temperature are the only real possibilities. I use a bottle of ISO heat every other tank or so, and always use premium fuel and have only ever iced up once in 11,000 mile's.

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