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Thread: 81 atc250r cylinder swap

  1. #1
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70

    81 atc250r cylinder swap

    Will a 78 cr250r cylinder fit on a atc250r case.

  2. #2
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    Does anyone know if the stud spacing is the same or close enough to modify on these two cylinders. My friend has the late 70s 250 bike engine with stock bore. My 81 atc250r is .080 over the cylinder is trashed. Don't have a machine shop in my area to put new sleeve in cylinder.

  3. #3
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,737
    Quote Originally Posted by TRIPOD guy View Post
    Does anyone know if the stud spacing is the same or close enough to modify on these two cylinders. My friend has the late 70s 250 bike engine with stock bore. My 81 atc250r is .080 over the cylinder is trashed. Don't have a machine shop in my area to put new sleeve in cylinder.
    Fill out a form and mail it to LA sleeve. They can put a new sleeve in and set you back up on OEM bore. You can also get a piston kit.
    Feedback for yaegerb: Click Here

    Need something blasted or polished or both? Send me a PM

  4. #4
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    Pick up that 78 250r cylinder look real good. Going to pull the cylinder off the 81 atc250r and hopefully it bolts on.

  5. #5
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    Not a direct bolt on! The holes are off by 1/8 side to side and 1/16 front to back. Going to try to make it fit got nothing to lose anyway and the cr jug has a bigger intake manifold.

  6. #6
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    The cylinder sleeve is moved forward 3/16 so I'll have to get that right before I start grinding on stud holes.

  7. #7
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    Just incase someone is paying attention to this I'm going to get the atc250r gasket and use it as a template on the elsinore cylinder. Been snowing here in northeastern arizona so I've been out snowmobiling alot and haven't had the time to get to this project.

  8. #8
    Join Date
    Aug 2020
    Location
    Snowflake Arizona
    --
    70
    Got a atc cylinder that's a stock bore so not going to modify the cr jug to much work once I got the new gasket and tried to line it up with the direction it needed to sit

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