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Thread: need to know carb size for 82 250r

  1. #1
    Join Date
    Dec 2006

    need to know carb size for 82 250r

    I have a 82 ATC 250r that I am rebuilding. The people I bought the bike from put a huge aftermarket carb on it and i am wanting to go back to stock, mainly because I have to replace the piston (it was fried), and I dont know how to jet the carb for the right air fuel mixture. I need to know one of two things. Does anyone have a proven combo to make the bike run faster (carb size and jet info for correct air fuel mixture), OR does anyone know the size of a stock carb for a 82 atc 250r. I was on ebay and someone had one off of a 84 and they said it was a 31 mm. I just need to know the size or point me into the right direction of where I could find that info. I do have a manual, and it does not tell what size the carb is for the bike. ANY help would be appreciated. Thanks

  2. #2
    Join Date
    Nov 2005
    the stock size is 27 mm wich i think is a little small!

    maybe try the '84 carb en try the stock mixture of that one.

  3. #3
    Join Date
    Jan 2009
    I have a 82' with a 34mm. I tried to go back to stock and it ran like a 185. It was bogging out. I fell in love with the speed and reliability of a 34.

  4. #4
    fabiodriven's Avatar
    fabiodriven is offline Aspiring romance novel cover model, and the Official 3WW slayer of thieves and swindlers. Catch me if you can
    Join Date
    Jun 2008
    The woods
    Yeah, 27mm is wayy too small for those engines, although that is what they had on them from the factory. I'd go with the 34mm if I were you.
    85 Tri-Zinger 60
    85 ATC250SX
    86 ATC250SX
    87 ATC250SX
    02 XR650L conversion
    84 ATC 480R

  5. #5
    Join Date
    Jan 2023
    Santa maria California


    I have an 82 atc 250r engine.what is the stock carb size and model number I can't find anyinfo for one

  6. #6
    Join Date
    Jan 2012
    Carthage NY 250r rules
    Stock 81-82 is 27 pe like stated and are to small .I'm running a 38 Mikuni tmx from a 01 cr 250 on my 83 250r.Runs great .
    250r rules

  7. #7
    Join Date
    Oct 2002
    I'd think you could jet a 36 or 38mm Mik without an issue. Amazing to know they called for a 27mm...
    All our government does is distract us while they steal from us, misspend our tax $ and ruin our country

  8. #8
    Gripit'n'ripit's Avatar
    Gripit'n'ripit is offline At The Back Of The Pack Arm chair racerAt the back of the pack
    Join Date
    Nov 2007
    Rochester NY
    did a first gen build. started with the stock and it was SLOOOOOW....but reliable. Moved to a 34mm carb, took maybe 3-4 kicks to start.
    81 250R Custom
    83 250R (in progress)
    98 Scrambler 400
    03 Bombardier Quest 500
    07 Polaris Predator (sold to klondike1020 )
    68 VW Dune Buggy

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