Carby Carb problem

Discussion in '2-Stroke Engines' started by Irish John, Mar 15, 2008.

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  1. Irish John

    Irish John Guest

    I've just built a 70cc 2-stroke and have taken it for a test run. All is OK except the engine dies off if I open the throttle to full on a hill. How can I eliminate this so full throttle is restored?

  2. kimhas

    kimhas New Member

    Hallo, I also build i bike with a zbox 80cc motor. I have the same problem. It goes good in lower speed and when its flat but when i give full trottle its no response. spesialy when its uphill
  3. RdKryton

    RdKryton Active Member

    I'll try to help. sounds like the carb is set wrong.
    Here's a link with a similar question.

    Also check for proper plug gap. It's very important. There is a sparkplug wire upgrade that helps too. You will need to search for that link. I have to run for now.
    Good luck

    Last edited: Mar 24, 2008
  4. Irish John

    Irish John Guest

    Solved Carb problem

    I solved the carb problem by moving the clip in the carb needle to the lowest groove on the needle - i.e. the one nearest the pointy end. It was being starved of fuel on the higher setting. I've done it on 2 engines now and the problem is solved.
  5. fetor56

    fetor56 Guest

  6. fetor56

    fetor56 Guest

    Yep man i figured u would have already tried message was more meant for kimhas but the general message of giving it time and distance still applies.
    Last edited by a moderator: Mar 24, 2008
  7. Irish John

    Irish John Guest


    I think it was Fetor (Thanks so much for that) who told me about the carb needle settings and it confirms what a really knowledgeable motorbike mechanic also told me. This problem would not have ironed itself out over time. It needed done straight away. I find the majority of my motors are improved on that highest carb setting. It's all academic because soon I'll become a 4-stroker and can kiss good ridance to the HT. If the 4-strokes go Ok I can build and sell them - something I would never do with the HT because people would be forever coming back irate and angry. The motorbike mechanic mentioned above won't have a bar of these motors after doing a few rebuilds.
    Despite there being 3 different sizes of HT motor they all have the same ports and exhaust which just about tells you everything.
    Does anyone know what speed the chinese 4-stroke that comes with the Grubee gearbox cruises comfortably at? Is it similar in power output spec to the Honda GXH50?
  8. kimhas

    kimhas New Member

    Thanks for anwers. I have now take a trip with the bike. I im the run in periode so i take it easy. It goes better with the choke half on. So i also think its get to much air/ to little fuel. I will do the o-ring triks and adjust the needle and see if its helps. its around 0 celcius , mayby it is easyer to get it run smooth when its hotter outside.
    The oil/fuel is now 16/1. I think it will run better after run in when I can use less oil.. right?