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This topic contains 6 replies, has 3 voices, and was last updated by  Walt Gifford 3 years, 10 months ago.

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  • #52668

    Ray
    Participant

    I have a question.

    Can’t get my sons clone past 50 mph.

    I set the timing and gearing (18/54), but she just doesn’t seem to want to rev. Not sure what else I can do.  All calculations suggest she should be running around 70 mph.  I’m I missing something?  Everyone else seems faster.

    Thanks for any advice

    RSR

  • #52676

    tony zambos
    Participant

    Your engine may not have enough power for that ratio. Add four teeth to the axle gear and see what happens.
    Also go over the kart. About zero toe in/out with the driver in the kart and on the ground. The gears should be in the same plane. No bad links in the chain and the axle spins freely w/o a chain.

    LAD Specialties customer / tony kart / rotax / kt100

    • #52681

      Ray
      Participant

      Thanks Tony,

      Chain and sprocket are new.  Had 14/54 and ran 50 mph, so I thought maybe the 18/54 would give a little more top end, but nothing.

      He is running in stock class.  I just thought it seemed slow.  Maybe I have to play even more with timing.  I just don’t want to blow his engine apart and I don’t believe in cheating with hidden upgrades.

      RSR

  • #52678

    Walt Gifford
    Participant

    Do you have tech inspections?

    FAA certified jet engine and aircraft technician,
    Nicholson Speedway class champion 2001,
    Yamaha KT100 Service Center,
    41 years karting experience

    • #52682

      Ray
      Participant

      Yes Walt,

      There are tech inspections.

      RSR

  • #52690

    tony zambos
    Participant

    You had the right idea, but maybe you took too big of a swing at fixing the problem. To get 50 MPH with 14/54 gearing, your engine had to be turning about 6200 RPM. With an 18/54 gearing and turning the same 6200 RPM would get you to 65 MPH. But that’s if you could still turn 6200 which you may not be able to do with the loss of the mechanical advantage of the first ratio you used. Going from the 14t driver to the 18t was equivalent to dropping twelve teeth on the axle. Try dropping a couple of teeth at a time on the axle gear and see what happens.
    All of your speed does not come from the engine. Chassis setup and drive technique play a big roll in top end speed.

    LAD Specialties customer / tony kart / rotax / kt100

  • #52716

    Walt Gifford
    Participant

    There are certain upgrades that are legal like the CL1 cam. If you have a lift only rule you can run the mod2 cam. Did you get your head decked to minimum, did you lap the valves and set the lash at .002″? You need to set you ignition timing (30 on gas), it’ll be differently abled in the stock position.

    You’re not going to get much more than 50 mph on a short sprint track but you should get there 3/4 down the longest straight. 6000-6200 is a good number.

    Gif

    FAA certified jet engine and aircraft technician,
    Nicholson Speedway class champion 2001,
    Yamaha KT100 Service Center,
    41 years karting experience

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