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Thread: Carb

  1. #1
    Join Date
    Dec 2009
    Location
    Spring Valley Il
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    168

    Default Carb

    What would be the proper carb for a 1978 Ski Doo TNT 440FA? Came without a carb.

  2. #2
    Join Date
    Dec 2009
    Location
    Baudette, MN
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    1,878

    Default

    Would have guessed a Mikuni and that appears to be the case. Found a chart that has some information but oddly it doesn't list a 440 F/A for 78. Only lists this engine for 77. In any case, the carb listed for 77 would probably be fine.

    Year Model Carb E-Ring Position
    (From Top)
    Air Screw
    (+or- 1/4 Turn
    1977 TNT 440 F/A VM36-53 2 1

    Have to confess, I don't know what the "53" amplifier means (but I'm sure someone does).

    This chart leaves out some key information: main jet size, pilot jet size, needle jet size, etc. If you ask 50 people you will probably get 50 different answers but you might get a feeling for what most people are running. I got lucky on my Cyclone; ordered a carb from Dennis Kirk and it's run perfectly for three years with the jetting it had when I got it.

    One other thing to consider is the type of choke setup. If the original cables are there, the choke cable should tell you whether it was the round plunger style (preferred in my opinion) or a lever style. Mikuni's can be bought with either configuration. Replacement carbs are pretty reasonable, maybe in the $90 - $120 range.

    If I ever run across some jetting info, I'll pass it along. Good Luck!!
    Last edited by skiroule; 05-30-2018 at 01:23 PM.

  3. #3
    Join Date
    Dec 2009
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    Baudette, MN
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    Default

    OK, after taking three tries to get the basic carb info right, I'm starting to see the confusion. As is the case with many of these old sleds, yours seems to be shrouded in a bit of mystery. Try as I might, I cannot find any documentation indicating that the 440 F/A was available in a 78 TNT.

    I'm thinking there are three possibilities: 1) It's really a 77, 2) someone swapped in a 77 engine, or 3) you have a one-off 78 that maybe resulted from some guys having fun at the factory.

    In any case, I haven't found any carb specs that positively confirm the 440 F/A factory carb settings but my impression based on what a couple of guys have said is that it would have been jetted pretty heavy (maybe 350 main and at least 35 pilot). That should at least get it running.

    It's probably applicable to multiple years so you may find this useful. It's a link to a 78 shop manual pdf. The carb specs are on page 399 but I'm sure the 440 specs are for a F/C.

    http://www.vintagesnow.com/Ski-Doo_f...p%20Manual.pdf

  4. #4
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    Dec 2009
    Location
    Spring Valley Il
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    My bad. Just looked and in pics it may be "fc" . Kind of hard to see. Sleds are still in barn should be home in a week or two to start these projects. Thanks and sorry for confusion.

  5. #5
    Join Date
    Dec 2009
    Location
    Baudette, MN
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    Default

    Quote Originally Posted by lotoftoys View Post
    My bad. Just looked and in pics it may be "fc" . Kind of hard to see. Sleds are still in barn should be home in a week or two to start these projects. Thanks and sorry for confusion.
    Given the number of manufacturers, models, and engine/clutch/carb combinations, confusion is a common experience with these old sleds.

    The good news is, if it is in fact a 78 fan cooled engine, pages 398, 399 of the previously mentioned shop manual give you the exact carb setup for that engine. Think you're in business!

  6. #6
    Join Date
    Dec 2009
    Location
    Spring Valley Il
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    Default

    Thanks skiroule!

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