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Discussion Sports muffler & re-jetting - Across

Discussion in 'Suzuki 250cc In-line 4's' started by laverdagraham, May 19, 2017.

  1. laverdagraham

    laverdagraham Active Member Premium Member

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    Hi everyone. Just wondering if anyone has fitted a sports exhaust system to their 250 Across?? I am trying to adapt a "Bandit" exhaust system that has a free flowing muffler to my 1992 Across to see if there is a performance increase, and the subject of carburetor jetting has been raised. If anyone has altered their system in the past, was there any requirement to re-jet the carbs to compensate for the additional air flow???
    Graham.
     
  2. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    most testing in that regard outside of using a Dyno usually involves doing a plug chop - WOT runs in a higher gear then snatch the clutch and kill the engine - then check the plug for colour

    If it's more free flowing then potentially then slightly larger on the main and work from there...

    Or if the engine specs are identical in all regards then check the carb main jet specs and see if there is a difference...

    Hopefully someone with actual experience can chime in with a formula for guided changes
     
  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  4. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Fit it, try it and see if you need to change anything from there.
     
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  5. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    That's a great read and just looking at the both the magnitude and direction of the various jetting changes to get the pod filters working, no wonder most efforts to run pod filters fail
     
  6. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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  7. ruckusman

    ruckusman Well-Known Member Premium Member Dirty Wheel Club

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    If I didn't know any better I'd say you're giving me home work - question for you, will there be a pop quiz :prankster::prankster::prankster:
     
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  8. laverdagraham

    laverdagraham Active Member Premium Member

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    Some good information here guys. Thanks for the advice, I will go for the "suck it and see" method I think.

    Cheers, Graham.
     
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  9. laverdagraham

    laverdagraham Active Member Premium Member

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    Exhaust system fitted, and test ride indicates that lower end power has been sacrificed a little. Top end however is much improved with a 14500 rev limit now raised to 16500 and still winding out.
     
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