Home Forums 2-Cycle Racing kt100 no speed

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    • #26471
      Michael perez
      Participant

      So I got my kt100 running but it only reaches about 5mph or lower I believe both needles H and L are set correct so what could it be? Could fuel be an issue. I’m running 100ll with redline. What should the carb been set too. I’m so close to racing I can taste it just trying to get that last push.

    • #26475
      tony zambos
      Participant

      A couple of questions. Will the engine rev cleanly on a stand? What do have for gearing? How old is the fuel and how much oil are you using? Is your brake draging? Is the carb throttle plate opening up fully?

      LAD Specialties customer / tony kart / rotax / kt100

    • #26532
      Michael perez
      Participant

      The engine will rev up on the stand but after a while it stalls. I do not know if the brake is draging.

      • #26581
        patrick hubbell
        Participant

        1) Has the carburetor been rebuilt recently? If not, put a diaphragm kit in it. Remove the pump cover(aluminum) Check the fuel inlet screen for debris. check that the hose attached to the pump cover goes to the crankcase fitting.

        2) set the H needle to 1/4 turn(for pipe) and the L needle to 2 turns. With these settings the engine will not idle.  You can make a KT idle by setting the L needle to 1/2 – 3/4, however there is not enough fuel at 3/4 to get out of the pits.

        3) Use Race gas like VP or ERC (100 octane). and mix 8 ounces of castor oil(Blendzall green label) to 1 gallon.

        4) Install a new fuel filter, watch the arrow for direction.

    • #26582
      tony zambos
      Participant

      OK, let’s start with the brake. If there is 1/16 to an 1/8 inch gap between both sides of the rotor to the brake pads, we’ll assume that the brakes are not dragging. Now, let’s start with two things, the carb and the clutch. How much do you know about them and have you made any changes to them?

      If the engine dies while idling, wouldn’t be too concerned unless it doesn’t fire right back up.

      Let’s check the clutch first. Put the kart on the stand with the tires firmly bolted on. Fire the engine, let it warm for a bit. With a little throttle, you should be able to lock the rear wheels without the engine dieing. The clutch shouldn’t be set to stall until 7,000 RPMs. Typically, the stall speed should between 8 and 9K. When adjusting the clutch, start at the bottom and slow increase the stall speed. Never start a stall speed at 11K and work your way down. If you do, the clutch will just turn into smoke.

      Now for the carb. Start with a clean air filter. With the filter off, make sure the butterfly is wide open when the throttle pedal hits its stop. If the carb hasn’t been rebuilt in a while, consider a rebuild kit. That way you’ll know the pump is in good condition. Do you have any idea what the fulcrum height is and the pop off pressure? Do you have a Flex-T in the low speed jet? Since there is no choke on this carb, the fuel mixture has to be on the rich side to get it to fire. Once it’s running, it will need to be leaned out with the low end jet. When you start to take off, does the engine rev cleanly or does it like BLAA, BLAA, BLAA. The carb could be just too rich. You never said where you had the needles set to. Every carb is going to be a little different and the pop off is going to effect the needlee setings. Try a pop-off between 9 and 11 psi, and the needles set to 1.5 to 2.0 turns out from the seat for the low end and between closed and a 1/4 open for the high.

      Make sure you have the right plug in and that it is not oil fowled.

      LAD Specialties customer / tony kart / rotax / kt100

      • #26671
        Michael perez
        Participant

        OK so I opened up the carb no debris in the strainer. To get it to take off a little I half to put 3 1/2 turns on the low and it just stall before it really gets going. And when it idles on the stand the engine surges. What should the cylinder compression be on a compresion test?

    • #26583
      tony zambos
      Participant

      Patrick types faster than I do. +1 for his comments

      LAD Specialties customer / tony kart / rotax / kt100

    • #26634
      Michael perez
      Participant

      For check brake drag i have a floating rotor so how do i go about that? By eye it looks good but the rotor never sits straight tell I start rolling. If it is on the kart stand and I hold the tire it will stall I have an old host man dxl clutch. I will try everything tomorrow and get back to you guys. Thanx

    • #26836
      tony zambos
      Participant

      Michael,
      You haven’t mentioned what the pop-off is set to. The minimum cylinder pressure should be 160 psi. To check, pull the plug, screw in the tester, disconnect the TCI, shut the fuel off and spin the motor up. Try a couple of times to verify the result.

      What is the condition of the pulse line? It should have a fit tightly at both ends, show no signs of cracking, not kinked and be pliable. Is there a tightly installed tie-wrap of safety at both ends?

      LAD Specialties customer / tony kart / rotax / kt100

    • #26838
      tony zambos
      Participant

      Michael,
      Before you get too deep into your motor, think about finding a good engine builder in your area. Best place to look for one is at the track you’ll be using. This might be the best, the fastest, the easiest and cheapest way to get to the track.

      LAD Specialties customer / tony kart / rotax / kt100

      • #26858
        Michael perez
        Participant

        Tony I’m not sure how to read pop off. I used to drive easy kart 125cc (never really messed with the carb to much so im new to this) but it was stolen 5 years ago than I bought a crg last year when I moved to Atlanta. Kt100 was the cheapest engine I could buy to practice on and when I bought it the only two cycle shop around closed down I try to look online for info but everyone says 100 different things. Don’t have much money because I’m in school just trying to get it running to get seat time. So today I took it out and tried a different route I started out of my stop position with the H needle 3 turns out got it to around 30 mph than turned it to 1  1/2 where it reached 45mph any more in it just bogs down. If anyone on this forum could give me a call to help me out or point me to what I would by doing I would greatly appreciate it. P/m u r number

      • #26860
        Michael perez
        Participant

        Pulse line is perfect snug no cracks and tie wraps to secure it so is the main fuel line.

    • #26886
      Daniel White
      Participant

      Contact Rick Sweeting at Raceway Motorsports. He is in Stockbridge (south of Atlanta) and knows the KT-100 quite well. His shop # is 678-860-0835

    • #27599
      Brian Mead
      Participant

      Don’t worry about idle,  they don’t have to,go back to the first settings, change the plugand as others said, throw a carb kit at it.   the pumpers will stretch. The engine surge you mention may be an air leak, you may want to pull the motor off,  take off the pipe and carb and dunk it in a tub to check  for bubbles.  I once had a leak around the spark plug, thin copper gasket and life was good. If  its running at all you’ve got enough compression to get it on the track  running, but the best idea may be sending it to a shop. you would be surprised how inexpensive  builders can be to fix minor problems.  Don Grainer and his crew at L.A.D.  have seen about a billion yamaha’s (including mine) and I’m sure they could help. Hope you get it running.

    • #26874
      tony zambos
      Participant

      You’ll need a guage similar to this one found on the Comet site.
      http://cometkartsales.com/Carb-Popoff-Gauge-0-30psi.html

      If you feel comfortable pulling the head off and can torque it properly back down, pull the head. Check for damage. If you want to be a little braver, pull the cylinder, but careful not to damage the base gasket. If there is any damage, pack it up and sent it to a shop. At this point, it doesn’t make sense to just hone the cylinder and put a new piston and ring in. There might be issues with the bottom end of the motor, the lower end of the rod, the crank or crank seals. I assume you do not have the tools or expertise to open the crank case. A failure in the bottom end could be fatal for the engine.
      There are many good kt-100 builders up here in the north, including mine, but you probably don’t want to spend the money to ship it. Try calling TS racing in Homestead. Not a very long drive for you.

      LAD Specialties customer / tony kart / rotax / kt100

    • #26877
      Michael perez
      Participant

      Lol I’m in Atlanta and ts racing was here but the  track I’m at Atlanta motorsports park had a conflict with there leas now they are in Jacksonville a 6 he drive. I have built many engines for my such car so I believe I could do most of the work if I could find the specs for the engine. Do u know where I could find a manual? Thank tony.

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