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Help Which Jet Needle goes where??? ZXR250

Discussion in 'Kawasaki 250cc In-line 4's' started by TonyZXR, Apr 18, 2018.

  1. TonyZXR

    TonyZXR Well-Known Member

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    Hey guys pulled the carbs apart on my zxr250, all 4 at the same time....yess i know i didn't realise they were different. Anyway so the main jets are different sizes as specified in the workshop manual which is fine but the jet needles are also different sizes. 2 have one number and the other 2 have a different number? Another set of carbs i pulled apart all 4 jet needles had the same numbers. So my question is should all 4 be the same or should there be 2 out of 4 different and which orientation do they go ?
     
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    A or C model?
     
  3. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    That's a good question. Needles are normally the same across all 4 carbs, just the main jets differ a little from the outside cylinders and the inside cylinders. Can you post the needle numbers?
     
  4. TonyZXR

    TonyZXR Well-Known Member

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    the A had the different needles , i think the spare set may be off a c
     
  5. TonyZXR

    TonyZXR Well-Known Member

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    ok so 2 of them are marked N76A and the other 2 are marked N52X, can't remember what the other set was as i put them into the bike
     
  6. sharky

    sharky Well-Known Member

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    I have only come across the N76U needles in both A & C models, the last lot of A model carbs though were adjustable but still marked 76U. 20180418_150848.jpg
     
  7. TonyZXR

    TonyZXR Well-Known Member

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    so they should have n76u in them , wonder why these are different
     
  8. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Could be previous bodge jobs, creating one good set from bits, possibly even a proper tune by someone who knows what they're doing... If they run OK leave them alone unless there's a problem.
     
  9. TonyZXR

    TonyZXR Well-Known Member

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    yeah i put the 4 of the same in it , was running poorly before , i suspect the rectifier issues and the messed up carbs being the reason the bike was parked in the first place
     
  10. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Carb issues on the ZXR are usually air leaks. Culprits are the rubber manifolds, leaky vacuum lines and/or missing airbox seals. Pilots should be set to 2.5 turns out as a starting point.
     
  11. sharky

    sharky Well-Known Member

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    Just checked the Megazip parts list & to make matters confusing, those needles are genuine numbers. C model Screenshot_2018-04-18-16-35-10-1.png A model Screenshot_2018-04-18-16-34-07-1.png
     
  12. TonyZXR

    TonyZXR Well-Known Member

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    it runs well now, i have fixed the cracked in the cylinder 1 boot, replaced all the vac lines and orings, jetting is 2.5 out , only thing that isn't good is the airbox seals , need to get 4 new ones and repair all the broken screws, someone has snapped off more than half of the screws in the carbs that hold the airbox on
     
  13. TonyZXR

    TonyZXR Well-Known Member

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    jeez talk about confusing
     
  14. TonyZXR

    TonyZXR Well-Known Member

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    well looking at that same diagram it appears they do specify an inside and outside 543567d7b47234b090d23c070917083e.png
     
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  15. TonyZXR

    TonyZXR Well-Known Member

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    wow just had a epiphany it does appear that that they are the right needle jets, the n76a goes on the outside carbs and the n52x goes on the inside carbs
     
  16. sharky

    sharky Well-Known Member

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    Ahh well spotted, was just a blur on my phone
     
  17. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Is this diagram of an A or C model carb setup?
     
  18. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    Well, that actually makes some sense. Running C carbs on an A engine can be difficult (I know). The C model engine has the extra hosing/plumbing for the Vacuum Valve that the A engine goes without. The A engine makes its power a little lower in the rev range, so running C carbs on one could give poorer fueling to the power curve!

    Like Sharky, I've only ever seen one needle type. But that might be because all my carb sets are for an A engine.

    Sharky.jpg
     
  19. TonyZXR

    TonyZXR Well-Known Member

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    that diagram is of a 1990 A2 model, the needles i just pulled out that i had in previously were all n76u also the other carbs had leaner jetting which would probably make it off a c, also me running the bike without a fuel filter has caused it to injest alot of dirt from what i can see. also i have adjusted the floats incorrectly , do the springed pins need to be compressed or uncompressed when measuring the float height?
     
  20. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    Float heights must be measured with the tang resting on but not opening the float valve.
     

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