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Help Acceleration Issue - 1990 ZXR250R

Discussion in 'Kawasaki 250cc In-line 4's' started by Sweeks, Aug 28, 2021.

  1. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Sounds like a good plan to get to the bottom of this mystery.
     
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  2. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  3. kiffsta

    kiffsta Administrator Staff Member Contributing Member Dirty Wheel Club

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    I thought the sp carbs were 32mm inlet diameter so how will a set of 30’s fit the inlet manifold ?

    I’d be looking at the slides , at 6000-7000rpm, you are on the main jet with the slides coming up , where are your needles set to ?
     
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  4. Sweeks

    Sweeks Active Member Premium Member

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    Please explain “where are your needles set to ?”, they are held in the slide by the spring, I haven’t made any changes to them.
    The slides are free and I have checked the diaphragms for leaks.
    These are my first CV’s, any guidance is appreciated.
    I still believe that there’s something going on with the slides, I just don’t know what.
    As you know, you can get to 7k with very little throttle opening, so I’m not sure that I’m getting on the mains fully.
     
  5. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The air filter element and air box sealing is all good?
     
  6. kiffsta

    kiffsta Administrator Staff Member Contributing Member Dirty Wheel Club

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    Sorry , are the needles shimmed ? Ie has some used washers to raise the needle height ?
     
  7. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    Are the Leak Air Jets clear?

    upload_2021-9-9_17-55-39.png
     
  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Standard ZXR 30mm carb needles are non-adjustable. No clips. You can only shim/space them to run richer. In the event you need to lean it off, it's either find a set of adjustable ZXR needles (rare) or change the air jets, which are pressed in.

    I have a set of adjustable needles I got off @sharky some time ago.
     
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  9. Sweeks

    Sweeks Active Member Premium Member

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  10. Sweeks

    Sweeks Active Member Premium Member

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    Yes, all good (Litetek seals )
     
  11. Sweeks

    Sweeks Active Member Premium Member

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    Same part number.
    Carb spigot O.D. Same
     
  12. GeorgeT

    GeorgeT Member

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    This sounds like it could be a CDI/TCI issue, i.e., the spark is too short when the rpm reaches a certain point so the spark is too close to the top-dead-center, like trying to run the engine backward almost. I have no idea if this bike used a CDi or TCi but the TCI as far as I am aware enables a longer spark at higher rpm. Older engine systems would just need the spark advanced more to enable smooth running as rpm increases. Maybe worth checking I guess?
     
  13. kiffsta

    kiffsta Administrator Staff Member Contributing Member Dirty Wheel Club

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    the symptoms are the same as my old zxr250 where the fuel inlet t piece seals had failed.


    I would be check the carbs for leaks , put the airbox on and spray some ether ( we have stuff called start you bastard) around the fuel inlet t piece , just a small spray and make sure that t piece is sealing correctly , if the revs rise then there is still a leak.


    I have doubts it is the tci, but never say never
     
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  14. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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