Carby Loctite...don't forget the carb

Discussion in '2-Stroke Engines' started by Skyliner70cc, Apr 6, 2011.

  1. Skyliner70cc

    Skyliner70cc Active Member

    I have a list of things to do on a new build and occasionally I don't follow my own tips. I got a new Speed carb installed on one of my bikes recently and during a ride, the throttle got stuck at full throttle. My engine is pretty powerful but handling the emergency was a no brainer and I got back safely.

    So, what caused the stuck throttle? The main carb jet assembly unscrewed itself from the carb causing a lateral pressure on the needle which prevented it from returning to idle position. I didn't follow my own advice and loctited the carb main jet to prevent this issue from occuring. This is only the 2nd time that this has happened in the past 6 years and I wanted to share it with you so you could consider doing this to your bike too.

    Please practice emergency procedures on your bike so when you have an issue, you can react instinctively and not put yourself in unnessary danger.

    1. Emergency panic stopping.
    2. What to do with a runaway engine
    a. hit kill switch and if doesn't work
    b. with one hand, pull plug wire off plug and if you are unable to do that
    c. move choke lever into full choke position
    d. if that doesn't work, while maintaining control of bike, disengage clutch and stop and then pull CDI/plug wiring
    3. practice reaction to sudden stoppage of rear wheel....amazing how many folks don't know how to handle bike when tires are skidding.


  2. bluegoatwoods

    bluegoatwoods Well-Known Member

    Good point.

    Runaway powered vehicles are not all that common. At least it's never happened to me or to anyone I know. And the stories you hear on the news might be overblown.

    Yet something like this, a stuck throttle cable, is so plausible that you have to wonder why it doesn't happen more often.

    In any case, we ought to keep in mind that the engine can be killed manually and that we might need to do it.
  3. Skyliner70cc

    Skyliner70cc Active Member

    Yeah, runaways are very rare and pretty much a non-issue in automobiles. Except for several caused by carpet mats getting stuck in the accelerator pedal on Toyotas, the remainder unintended acceleration were caused by driver error.

    I did have a runway vehicle once though. It was when I blew a turbo on my diesel and the oil that is used to lube and cool the turbo was sucked into the intake and the engine used the oil as fuel. With no throttle (engine power is controlled soley by amount of fuel injected into a diesel engine) to block airflow, the engine went past redline very quickly and the acceleration was very impressive. I did the only thing I could do and put the engine in neutral and as quickly as I could, pop the hood and throw the t-shirt I was wearing into the intake. :grin5:'

    My first runway on the bike was caused by a defective carb. The carb cylinder that the needle valve assembly sits in wasn't perfectly round and when engine heated up and carb heated up, it deformed just slightly more to cause teh carb to get jammed. Several minutes of light honing with a brake cylinder honing tune fixed the problem.
  4. bluegoatwoods

    bluegoatwoods Well-Known Member

    Now that I think about it, though, my oldest daughter did cause my first MB to runaway a bit with her on it.

    When I looked into it, I found that she or one of her sisters had yanked on the throttle hard enough that it had twisted off the little plastic nub on the inside that seats in the hole drilled in the handlebars. They then went on to twist the whole assembly around to the point that the cable would not fully retract.

    She no longer wishes to ride my MB.


    The whole episode wasn't quite as dangerous as a true runaway would be. But it was nerve wracking for a moment or two. I'm surprised that it's fading in my memory.
  5. Skyliner70cc

    Skyliner70cc Active Member

    scary. i could see that happening.