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Discussion Aftermarket headers vs stock ZXR250

Discussion in 'Kawasaki 250cc In-line 4's' started by H05TYL, Oct 29, 2022.

  1. H05TYL

    H05TYL Active Member

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    Has anyone done any back to back testing or comparison between stock headers and aftermarket headers? 4-2-1 vs 4-1? Or versions with shorter primaries?

    Just swapped this stainless number from my parts bike on to my good one but haven't had a chance to ride it yet because it's pouring down outside.
    IMG20221029144822.jpg IMG20221029144834.jpg
     
    H05TYL, Oct 29, 2022
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  2. Frankster

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

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    I'll be keen to see what difference (if any) it makes. I guess the collector being closer to the exhaust valves might draw the combusted charge out a tiny bit quicker and help pull in the new charge, but my thought is that it won't make any difference at all. I will be happy if it does.

    Also, do those stainless Steel headers have an expansion cone as they attach to the head like the normal ZXR pipes do?
     
    Frankster, Oct 29, 2022
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  3. gregt

    gregt Well-Known Member Premium Member

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    Shorter primaries raise the rpm where the torque peak occurs. The systems appear to have roughly the same overall length so the HP peak will still happen at the same rpm. Without any other mods it'll probably give a slightly narrower power band. Maybe with a sharper entry = which could feel like more power.
     
    gregt, Oct 29, 2022
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  4. H05TYL

    H05TYL Active Member

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    It's not a cone, but they do step up in diameter just after the flange.

    There seems to be a lot of different designs available from the aftermarket, from super long 4-2-1 systems,

    [​IMG]
    to 4-2 systems with twin silencers,


    [​IMG]


    and long, medium, short primary 4-1 systems

    [​IMG]


    Interestingly the new zx25r has pretty short primaries (possibly for packaging reasons) and crossover tubes between each
     
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    H05TYL, Oct 29, 2022
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