Forums 🚥 PiT STOP 🔧 Hyosung Technical Help 2010 gt125 comet not running correct, UNSURE

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    • #3894
      • Topics: 1
      • Replies: 0
      Gr125 comet

      Ok so my bag of sh*t has stopped working, again! Running rich on the front as front spark plug was sooty, Rear was fine. Still has 0.7mm gap too! Cleaned airbox and carbs still won’t start/run without choke on any blip of the throttle it cuts off etc.. any ideas as it’s v v close to being set a lite lol. About to take the carbs apart again for the 4/5th time since owning the bike in the last 3years!! Any advice etc would be awesome!

    • #3899
      ♠️ MARCEL
      • Topics: 45
      • Replies: 1,892
      North UK


      If we get the electrics out of the way first (spark) then we can deal with the “fuel”  & “air” elements of the situation you’re having.   If unsure of what to do, I may quote one of the replies i made on an earlier topic similar to this…  So get a meter out and probe the following….

      • Confirm the stator blue/green plug is 100 ohms optimal (bike turned off & COLD)
        (that’s your flywheel sensor, tells your CDI what to do as it spins and sends spark signals)
      • Stator yellow plug has 3 pins so do Pin 1/Pin3 | Pin2/Pin3 | Pin1&2
        They must say UNDER 1 OHM (one number) as per books. (Bike OFF)
        Alternatively below:
      • Stator yellow plug (all 3 pin combinations)=> It must say 85V around 5k revs max
        (Bike running ofcourse, 85-99v is optimal from books)
        This thing is just as crucial as the reg to supply electrics or it wanes & bogs other parts down.  (aka ignition system starts from this thing)
      • Go to battery => Rev around 2k-5k max=> 14v-15v is what should be reported.
        (Any 13.x => replace the reg => whatever revs above 2k)
        (Connect the stator back while doing this)
        (Reg & stator go down with each other in tandem sometimes, common)
      • Now, turn whole bike off.  Go to your Frame Coils (front & rear) and confirm:
        A => HT lead (red meter) and FRAME ground (black meter) are 6,000 ohms strong
        B => Coil “TERMINAL PIN”  and “frame ground” => UNDER 1 OHM (one number)
        (0.6 is typical for a healthy unit)
        Do this for front and rear.  Write all hard figures down from all tests and let us know.
      • ========================

      Now to your intake system:

      • Spray carb cleaner UNDER THE MANIFOLDS going to engine….
        If revs change => Then you need to replace the intake O-rings under the manifolds.
      • Spray the carb intake rubber pipes
        If the rubber pipes change revs -> You may have a potential split or tiny hole leaking out on the rubber pipe itself.
      • Spray the “METAL CLAMPS” under the airbox holding the carb
        As before, if revs change, your clamps are loose or check the airbox HOLE isn’t cracked. The whole carb goes inside it.
      • Spray test the “metal clamps” holding the carbs to the manifold rubber pipes or check the rubber pipes didn’t get a slit/tear from the carb sitting on it (mouth openings at the rubber pipes)
      • Air filter should be secure and not dirty or it makes things boggy later on.


      Fueling side……

      • Your tap should be squirting fuel in to the filter every time you blip the throttle, if its a clear looking filter and isn’t dirty/clogged.
      • Fuel Pump rarely fails but particles can get to it if the filter is bad.
        You can open it and look through its glass window.
      • Strong vacuum is crucial to keep the taps & pumps pulsating fuel through.


      Carb side….
      If we get the above ^ checked, then carb is the last item to deal with. This is also assumed the mixture screws were not tampered with (should never be), then yes a mega clean top/bottom does wonders to it (it has many passages).   Carb will be as good as the sparking & air system  or vise versa.   The forum has the jetting tutorial, slide tutorial also.
      Float heights crucially to be 7mm exactly, that’s your fuel input control.

      Plug side…
      Conside the plugs may have wanned (not firing as good as before), and potential replacement may be warranted.
      Don’t change the gaps, even the basic CR8E is already 8mm as the books say keep the plugs unmodified or it will run strange, NGK already gapped them.   Just stay away from “IX” branded ones, they are junk.   Basic CR8E or Laser is enough for the hyosungs.

      Hope this helps, good luck.

      // Meditation doesn't mean you have to sit still....

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