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 2 years, 3 months ago.

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  • #76945

    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!


  • #76975

    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.
    Vintage B-Stock Pilot
    "When in doubt Gas it, It won't help but it ends the suspense."

  • #76978

    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.

  • #77974

    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** "

  • #78855

    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.

  • #79145

    Matt Dixon

    Do NOT run pump gas


  • #79425

    Carl Beavers


    Been there done that and it cost me a motor.

    +1 on the seat advise.

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