Problem : engine wont go proper speed

Discussion in '2-Stroke Engines' started by Ieataxolotls, Mar 19, 2010.

  1. Ieataxolotls

    Ieataxolotls New Member

    Hello people,

    Ive got a problem with my engine, cant reach a higher speed.

    When i throttle it goes ok for a bit, but then it reaches a certain speed that it vibrates a bit, but then slows down dramaticly. This repeats over and over again.

    Ive tryed replacing the intake manifold gasket and it fixed everything, but then after a while of riding it went back to before, i think i blew the gasket.

    So, i made a new gasket and it didnt work again

    Next step i did was to switch the carburator from my other motorized bike to this one.

    It worked fine but for some unknown reason it does not work anymore. (this carb still works properly on my other bike)

    So now i have completly switched both intake and carb from one bike to the other. which has not fixed anything.

    Can you tell me what the proper name for this problem is, so i can search it?
    What can do you people recomend i do next?

    i can explain more
    if you want.

    Thanks everybody :grin5:

  2. AussieSteve

    AussieSteve Active Member

    Before f@&#ing around more, put a new plug in, run it until it's warm or hot, at WOT as much as possible, then pull it out and check the colour. It should tell the story, if it's a carb/mixture problem.

    How are you sealing your carb to your inlet? ie Sealant, 'O' ring, nothing.

    Is it 4-stroking before it refuses to rev out? (See the 'four-stroking' link in NT Carb Tuning Basics)
    That might be the vibration.

    Does the situation improve with the choke partially on, (it's lean), or get substantially worse, (it's rich)?
  3. Ieataxolotls

    Ieataxolotls New Member

    Thanks AussieSteve for you highly detailed post.

    My sparkplug is black oily. (too rich)?

    I'm using a black silicon to seal the "intake -> carb" up.

    I haven't check if it is fourstroking yet (sorry)

    I have learnt a way to make it go full speed without dieing, i go slowly tease the throttle untill the engine sounds smooth, this allows me the go WOT and go warp speed immediately. But goes back to the problem as mentioned in first post when i slow down to a slow speed. I have managed to master the technique and make it to go fast in about 10 seconds.

    Can you tell what my problem is from this?
  4. AussieSteve

    AussieSteve Active Member

    Yep, too rich - even with a high oil to fuel ratio, (I run 20:1), a plug should be dry and light tan. (Maybe a bit of oil if you idle for a bit before shutting down the engine, but still tan, not black.)

    Most silicon sealants, including RTV types, are not suitable for use with fuel/gas/petrol. You need to use a fuel-resistant sealant such as Permatex non-hardenening or step up to a more reliable sealing method.

    One way is to slide an 'O' ring, (fuel-resistant), into the carb opening for the inlet to press against. If you push hard as you tighten, many people say that this method is reliable.

    Personally, I bought an after-market alloy inlet tube, (~$10US), then filed a groove for an 'O' ring. Perfect seal.

    Having said that, you don't have that problem, at the moment, but it's common.

    Do have a look at that video - it'll be worth the effort.

    Sounds like the above.

    If so:-
    1. Pull the carby apart, clean it thoroughly with solvent, (ie gas/petrol, remove jets etc to do this), ensure that the float doesn't have fuel in it, (a shake will tell you - any fuel would indicate a punctured float). Then blow out everything with compressed air and re-assemble.

    2. Re-test.

    3. If problem persists, consult a doctor...


    3b. Drop the slide needle one notch and try again. (Sounds, though, like you might need a smaller main jet and/or both.)

    Your air filter is clean and your exhaust isn't clogged?

    Someone else might be able to add more.....
    Last edited: Mar 20, 2010