Air Leak in Carby?? Brand new bike... so close to working!

Discussion in '2-Stroke Engines' started by SpenceDawg, Sep 11, 2016.

  1. SpenceDawg

    SpenceDawg New Member

    Hey everybody, I'm a total newbie building my first bike with the help of youtube videos and all your wonderful threads on this site. Excuse my lack of proper terminology as I attempt to describe my issue.

    After a couple days of work, I'm pretty sure everything is good to go except for what I think is an air leak in my carb (based on what I've read I think that's it). When I release the clutch after getting some momentum, the engine roars to life and immediately starts screaming as if I'm giving it full throttle right off the bat. I re-threaded the throttle cable into the carb and I think I did that right. The throttle housing is slightly busted, so that needs to be replaced for full functionality but it should work as is. However, when at starting position the engine is still running, and turning the throttle does nothing.

    So, am I right in assuming that this is an air leak in the carb? What should I do to attempt to solve this issue? Thanks!

  2. zippinaround

    zippinaround Active Member

    when you put the needle in make sure the groove is pointed at the idle screw a little slanted notch , then screw out the screw fully and put it back in 1 and 1/4 turns and try start it , you will probably need to screw it in a bit more if it wont start or if its cutting out.

    if that doesnt solve it then try tighten the carb clamp a bit that is usually where it leaks , could put some silicone around it too or get an o-ring to fit it.
  3. Frankenstein

    Frankenstein Well-Known Member

    2 things it might be, first is obviously an air leak, or it could be an improperly strung carb.

    If the barrel that raises up and down isn't in right, it will never close completely, and it will Rev like nuts. It has a small pin in the carb and a long slit along the barrel, they must be aligned together. I once had a problem where I could have sworn I had an air leak, I looked at everything and looked it over again... Bothered me for weeks as I tried everything except cracking the crankcase.

    Turns out my throttle adjustment barrel on the throttle assembly was loose until it was making a wide open throttle. It's like the ones on a brake lever to adjust tightness.

    You said the throttle housing is busted? You mean the part on the bars right? If the cable is pinched then that could make a problem, does the throttle twist back when let go?
  4. SpenceDawg

    SpenceDawg New Member

    That was it!! Just rode it around for the first time and it was incredible!! Thanks to you and everybody else on this forum!
  5. Frankenstein

    Frankenstein Well-Known Member

    Congrats! Have fun! Wear a damn helmet!
  6. zippinaround

    zippinaround Active Member

    Funny how something so simple and small can stop it from running , If you got a China girl I reckon you will be visiting here a lot haha
  7. SpenceDawg

    SpenceDawg New Member

    Hahaha yea I did, I'm assuming I'll be here a lot as well. Currently it isn't idling... off to crawl the threads!
  8. Frankenstein

    Frankenstein Well-Known Member

    I'm always here gathering info, helping, or trying to, thinking, pondering, learning, getting pissed or pissing off somebody else (it's the internet this happens) and discussing the best method towards achieving a goal.

    It's nice being able to interact with fellow enthusiasts and be able to help and receive help, I'm hands on so for the most part I can and want to physically do my own work, but acquiring the knowledge through the help of experts is the best part.

    Very interesting how different people find equally best results with a dozen completely different solutions. I think it must be the different climates and rising conditions that affect how a user decides what's the best version of a motorized bike.

    I need lots of low rpm power because of the city and hills and retarded drivers. Also need a nimble and tough bike with responsiveness to steering to stand up to rough crappy roads that are completely covered in potholes and roadkill and bumps and cracks and broken glass all while towing my 210lbs fat ass with 50 pounds of steel bike and motor. That motor has to push me through those obstacles quickly and reliably.

    So my set up is actually quite perfect for my needs. The only part I'm working on is reducing maintenance, looking at having a tougher cylinder, so far nikasil looks nice as a solution. If I can't get that then I will try for cast iron. My chains are pretty well figured out, I'm looking at chain repair/replacement roughly every 6 months, the lubricant outlasts the chain actually, I use a very special mixture of waxes and additives I developed which seem to be impervious to everything except gasoline, however the waxy coatings are still definitely there.

    I'm working on getting my crank finely balanced by following the work of jaguar, since he seems to have the whole thing figured out to a t, even has a calculator so all I have to do it break out a caliper and a jeweler's scale.

    Still working out bugs in the tire department, trying to reduce flats to twice a year vs every 2 months or so.

    Also been trying to work out a bike for the wife that's not complicated, light, and easy to use while being reliable and also strong enough to handle the roads.

    Just keep comming back till you can't no more.
  9. zippinaround

    zippinaround Active Member

    I agree I tinker away but if I'm ever left scratching my head it's handy to just ask here someone will come up with a solution .

    So turning the idle screw didn't fix it? What's happening now revving up high or cutting out?