Home Forums Shifter Karts 125cc Shifter Kart Help

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This topic contains 6 replies, has 7 voices, and was last updated by  Carl Beavers 11 months, 1 week ago.

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    Zane Hicks

    Pictures Here

    Hello all! I recently purchased a Honda 125cc shifter kart, but have not gotten to use it yet, I have a couple questions 🙂

    How would I go about putting in a larger seat/mounting it? Just maybe 1.5” on each side, right now it’s a squeeze to get in it.

    Since I do not plan on entering championships and would really just use this kart for fun, could I skip mixing the race fuel and go with straight gasoline? How would this effect performance?

    Thanks so much!



    Greg Wright

    As far as the seat goes get a seat that fits and adjust the left side (radiator side) seat strut by bending it until you get a proper fit.


    I wouldn’t run just pump gas, too much chance of detonation.

    Greg Wright
    Rapid Racing Inc.

    "When in doubt Gas it, It won't help but it ends the suspense."


    Jack Cook

    The seat needs to be very snug just sitting in it. On the track you need that tight fit and you won’t notice the tightness. I loose seat in a 125 shifter is not good and could bruise your hips from moving around.


    Ben Lewis

    +10 on the seat good advice here. I can barely fit in mine but then as soon as I get moving I don’t even notice.

    Run c12 you’ll be glad you did. When I first started w the S-M 125 I used 98 pump gas and after 6-8 weekends had a detonation ring which made both the head and cylinder worthless. That was over $350 to replace. I generally run 4-5 15min sessions on a practice day and rarely use more than a gallon to gallon 1/2. At ~$20 a day in gas for the c12 it’s a good investment. Plus if you’re planning on tuning a pwk/pwm with the right jetting race gas will help a lot in giving you stable readings.

    " Turd Ferguson is real and he will pass your a** "


    Robert Tifft

    +1 on running C12 since you can’t go wrong there. I ran “100” octane from a local 76 station pump which wrecked the piston and cylinder from detonation in only a few sessions. Turns out that fuel has a 95 motor octane. Recommended motor octane for these engines is at least 100 to prevent detonation.


    Matt Dixon

    Do NOT run pump gas



    Carl Beavers


    Been there done that and it cost me a motor.

    +1 on the seat advise.

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