Announcement

Collapse
No announcement yet.

carb issues/wont idle

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • carb issues/wont idle

    Hey,

    Any help would be hugely appreciated, i've run dry on my limited knowledge!

    I've got to the tail end of my build, i've put a pod filter on and a slip on exhaust.

    Which i've accounted for with bigger main jet and bigger pilot get and stepped the needle up too.

    But the bike wont start without the throttle rolled slightly, as soon as i let go it dies.

    I've had a play with the pilot screw and still get no luck.

    the bike is a Suzuki gn 125

    cheers

    danny

  • #2
    I've typed a detailed reply twice and lost my connection so here's a short version.
    Is your tickover screw in far enough to be working or is holding the throttle open a little do its job ?
    If that's ok, strip the carb and clean eveything with carb cleaner. Check the condition of everything as you reassemble it back to factory settings according to manual (float heights, airscrew, needle clip and pilot jet, leave the main up a couple of sizes to be safe ). Put it back together and try it.
    Have a fiddle and get back with what you find.

    Comment


    • #3
      Ah man thats annoying, Thanks for replying! tickover screw seems to engage, i can adjust either way but doesn't make a difference, if i turn it as far as possible in it's still not enough to start the engine. i still have to hold the throttle open, is there a way to make this engage more?
      i had the carb apart and cleaned all the parts before installing the new main jet and pilot jet (reassembling and testing between each) earlier this evening. Fiddling with it i'm still getting that issue of no idling.

      Whilst typing this i'm figuring the issue must be the tickover screw not engaging enough? could this be the right thinking?

      thanks again for your reply!

      danny

      Comment


      • #4
        If you can screw the tickover screw all the way in and it makes no difference I think we can rule that out (providing somebody hasn't cut the end off it or anything else stupid ). If you're sure that everything is totally clean and clear I would look at the airscrew setting and the float height first, if either of these is wrong it can make it hard for the engine to take fuel at very low rpm. Once you've got it started will it tickover or do you have to keep it running with the throttle ? Have you had a chance to give it a test ride or are you stuck with just being able to start it at the moment ?

        Comment


        • #5
          Originally posted by bluedog59 View Post
          If you can screw the tickover screw all the way in and it makes no difference I think we can rule that out (providing somebody hasn't cut the end off it or anything else stupid ). If you're sure that everything is totally clean and clear I would look at the airscrew setting and the float height first, if either of these is wrong it can make it hard for the engine to take fuel at very low rpm. Once you've got it started will it tickover or do you have to keep it running with the throttle ? Have you had a chance to give it a test ride or are you stuck with just being able to start it at the moment ?

          I'll have a go at both of them things, to be honest I'm pinning my hopes on float height!
          What do you think about pilot air jet? is this something I can swap for a smaller size to
          reduce to restrict airflow?

          cheers

          danny

          Comment


          • #6
            Pilot air jet ? You should have a main jet, a pilot jet and an air screw.
            The main jet is the big one in the middle as you look at the underside (102.5 std ?). The pilot is the small one (35 std ?) and the airscrew is the one in front of the diaphragm cover when you look from above.
            I'd start with a std pilot jet, main jet about 107.5 and the airscrew set as per the manual.
            After you've set the float height etc, start it up. Is it any better ? Next, turn the airscrew out another 1/4 turn ( this should add a little more fuel right at the start of the throttle.
            Any better?
            Yes ? Give it another 1/4 turn out on the airscrew.
            No ? Give it another 1/4 turn just to check.
            If it does get better, keep giving it another 1/4 turn till it's right. If you get to about 3 turns out from seated, put it back to std setting and put a 37.5 pilot in and repeat.
            Have you tried it without the pod filter ? Some off the cheap ones are very poor and cause all sorts of problems.
            How much throttle are we talking about to start it ?
            Google "cmsnl gn125" for a full parts diagram of your carb and the rest of the bike.

            Comment


            • #7
              yeah, this is whats confusing me, everything I've read doesn't seem to refer to it. It sits above the slide in the little chamber at the top, looks like this:

              https://www.ebay.co.uk/i/16113072775...7297426&crdt=0

              What do you think?

              Not had a chance to get in the garage yet, that'll be tonights job though!

              So maybe try without any filter?

              Only takes the smallest amount of throttle to get it going!

              thanks for your help again man!

              Comment


              • #8
                Google "cmsnl gn125" and look at the carb section. I believe you are referring to item #2. As far as I can see this will control the air flow rate into the "none vacuum" side of the slide diaphragm and thus the rate at which the slide can rise. I'd leave this stock for the time being.
                I'm talking about item #50, this adjusts the fuel right at the very bottom of the pick up, that bit where you "just" crack the throttle. There will be a stock setting for this in the manual.....or Google.
                Screwing it out from std should give you a little more fuel,screwing in less. (refer to what I put earlier about amounts).
                And, at the end of the day, some bikes like a little throttle to start. If it runs fine everywhere else and you can live with it .

                Comment

                Working...
                X