Airbox mods and fuel mixture?
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Thread: Airbox mods and fuel mixture?

  1. #1
    Senior Member Trail Woman's Avatar
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    Airbox mods and fuel mixture?

    Has anyone here done them? How did it work out for you?

    It seems to me the seat pan is the air scoop that sends air to the box and the snorkel in the box only restricts it but leaves a lip underneath so dirt/water won't slide down to the filter. Has anyone removed/modified this snorkel?

    It seems to me if I enrich the fuel mix by removing the welch plug in the carb to access the mixture screw, modding the airbox will balance it out with more air resulting in faster fuel delivery? Then you'd want stronger spark plug?
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  2. #2
    Super Moderator JerseyJeeper's Avatar
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    That is the theory, correct. Some say that the TW engine gets enough air and fuel (and exhaust flow) from the factory and that these mods do not help in the case of a TW enough to warrant them (other than a tad more open on the mixture screw).
    Trail Woman, Ken and jtstdub like this.
    Husqvarna TE300i Fuel Injected 2-Stroke 2019
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  3. #3
    Senior Member Trail Woman's Avatar
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    Unfortunately I've been on the forum long enough to know you're correct in peoples acceptance of TWs being a little under powered. It's nice that it doesn't get away from you easily and you can milk some performance out of it by how you ride it.....but I'm determined to get more out of it. I may have to get rid of the battery for a capacitor and metal tank for plastic while I'm at it. One mod at a time I'll get her running stronger.

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    Senior Member Fred's Avatar
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    You won't see much change in the flow rate of air through the engine with only airbox mods. What will happen with changes to the snorkel, air filter and/or air box are changes in the head loss, or pressure drop across the assembly. This changes the pressure differential between upstream, and downstream sides of the carburetor which is of course the driving force that meters gasoline from the tank into the engine. This is why a dirty, clogged air filter messes up the air fuel ratio by increasing head loss across the filter creating a rich mix and why opening up the airbox helps compensate for reduced partial pressure of oxygen as elevation increases that also would normally result in a similar too rich fuel ratio. You want that 16:1 ratio all the time for naturally aspirated engines running non-ethanol and since we don't have fuel injection with it's mass air sensors we have to manually try to compensate for changes in elevation, air density, temperature, humidity and regulatory environment ( California wants us leaner than 16:1 , thus we cheat with the supposedly sealed up inaccessible and mandated non-adjustable mixture screw).

    If you want to get the 196cc air pump to move more air and thus burn more gas making more horsepower via higher rpms then reducing flow restrictions is a proven approach. Larger valves mated to aftermarket exhaust systems can help but even with stronger valve springs to slam things shut quicker one will eventually face valve float and piston conflict. Longer duration cams don't help this either. Easier power-to-weight improvements include avoiding ethanol with it's lower energy density and reducing weight of bike,rider and carried gear. IBXR has a responsive TW with serious weight reduction coupled with 226cc and 6-speed upgrades at expense of some practicality like a starter motor, full fenders, horn, some lighting, etc...
    Last edited by Fred; 06-19-2018 at 07:23 PM.
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  6. #5
    Super Moderator JerseyJeeper's Avatar
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    Quote Originally Posted by Trail Woman View Post
    Unfortunately I've been on the forum long enough to know you're correct in peoples acceptance of TWs being a little under powered. It's nice that it doesn't get away from you easily and you can milk some performance out of it by how you ride it.....but I'm determined to get more out of it. I may have to get rid of the battery for a capacitor and metal tank for plastic while I'm at it. One mod at a time I'll get her running stronger.

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    Husqvarna TE300i Fuel Injected 2-Stroke 2019
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    Senior Member Trail Woman's Avatar
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    So more air + more fuel + larger jets + more spark + more open muffler..make woman ride trail faster?

    But seriously, start with the fuel mixture screw first then every other mods would have to balance each other?

  8. #7
    Super Moderator JerseyJeeper's Avatar
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    Yes, but I guess what i'm saying is that for the 196cc that this engine has, it has adequate airflow in and out in stock form and is just slightly lean. You may want to increase the size of the jug and up the carburetor size a few mm to get what you want. Even porting the head has demonstrated very little improvement. A lot of bikes are "dialed back" and will have substantial gains from what you want to do, not so much in this case (IMHO). You should have gotten the engine along with the wheel and swingarm you just got. That would have given you exactly what you are looking for.


    Quote Originally Posted by Trail Woman View Post
    So more air + more fuel + larger jets + more spark + more open muffler..make woman ride trail faster?

    But seriously, start with the fuel mixture screw first then every other mods would have to balance each other?
    Husqvarna TE300i Fuel Injected 2-Stroke 2019
    Yamaha XT225 - 1999 Serow
    Yamaha TW200Z - 2010
    Yamaha BW200 Electric Start! - 1986
    Yamaha TTR225R - 2003
    Husqvarna 701 Enduro - 2017
    Kawasaki Prairie 650 - 2002

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    Senior Member scotti158's Avatar
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    From what I've seen on the forum, you can spend lots of time and $ trying to get more performance out of the TW with little improvement.
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    Senior Member Fred's Avatar
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    Strive for balance Grasshopper. As Confucius once said: "It does not matter how slowly you go so long as you do not stop"
    2003 TW200 "Betty Boop"
    2006 TW200 "Nibbler", a.k.a. “Mr.Gizmo"
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  11. #10
    Senior Member Dryden-Tdub's Avatar
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    Quote Originally Posted by Fred View Post
    Strive for balance Grasshopper. As Confucius once said: "It does not matter how slowly you go so long as you do not stop"
    Confucius must have better balance than I do!



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