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Thread: Needing help with my 1986 atc 250r flutters at higher rpm

  1. #1
    Join Date
    Jun 2021
    Location
    Fort Worth Texas
    --
    6

    Needing help with my 1986 atc 250r flutters at higher rpm

    My 1986 atc 250r flutters at higher rpm range when riding. It will idle and rev great
    Without a load. Things that I have done

    New oem coil and ricks cdi box
    Carb cleaned and did a main rejet from 135-155
    Compression test 190 psi
    New plug
    New fuel 40:1
    New fiber reeds
    Any help will be greatly appreciated…..Aaron

  2. #2
    Join Date
    Apr 2011
    Location
    Mexico
    --
    9,003
    Have you experimented with your main jet size and needle clip settings?

    What color does your plug have after a top end run?
    It sucks to get old

  3. #3
    Join Date
    Jun 2021
    Location
    Fort Worth Texas
    --
    6
    Main jet was 135 changed to a 150 and it helped a little. Tried a 155 was worse
    Went back to a 142 it was better about like the 150. I have not adjusted the needle
    Factory Stock numbers on main jet is 145-165
    Plug color is black so I would assume it is running on the rich side

  4. #4
    Join Date
    Jul 2009
    Location
    South Florida
    --
    6,722
    Try your factory CDI box if you still have it ?
    If it still has the factory carburetor then it might be worn out .
    I recommend a keihin PWK 38mm with a 170 main jet .

    I chased a similar problem a couple years ago with new reeds on the factory cage , after trying everything else even a complete rebuild I finally just put Vforce 3 reeds and it cured the problem .
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  5. #5
    Join Date
    Jun 2021
    Location
    Fort Worth Texas
    --
    6
    Unfortunately I don’t have the factory cdi box. The one that was removed I still have it but it’s a dze Argentina made.

  6. #6
    Join Date
    Jan 2021
    Location
    NJ
    --
    24
    It’s probably the cdi causing it. My 85 had a non oem cdi and I replaced everything electrical and still would run right. It would idle all day and start on first kick but until I put a good used cdi it ran like the choke was on. If you search google about 250r cdi you’ll see a lot of people have the same problem using any aftermarket cdi.

  7. #7
    Join Date
    Jun 2021
    Location
    Fort Worth Texas
    --
    6
    The cdi box has been a concern from the get go. I would love to find an original
    Oem box but it is impossible. If someone has one please let me know.

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