Forums 🚥 PIT STOP 🔧 Hyosung Technical Help GT 250 I 2002 does not start, tried everthing

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    • #5430
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      Dear hyoriders.club,

      I just found this forum and can’t believe it exist. I thought nobody would ride Hyosung besides me.  😛 I live in Germany and have to explain to everybody what brand it is.

      Got my first Hyosung in 2009, a 125 GT Naked. Drove it about 30000km and loved it. Than i started college and had no time to ride and it was sitting in my dad’s garage for about 3 years. Than I got a job in 2014 and had a bit of money and bought a 250 Engine, 250 Frame, 250 Carburator, 250 CDI, Arrow complete exhaust, small koso speedo and a GT 650 Fork and brakes from ebay. Put it all together and got the engine running in idle for maybe 10 minutes. Than I dissasemble everthing and done a new (horrible) paintjob. Put it all togehther again and then,… bikes not starting. Done many things ( to much to explain here) over a long peroid of time and than i was super frustraded and a few more year gone by. Now in Nov. 2020 I wanted the Bike finaly to run again. Valve clearance is checked and perfect, I have compression and a strong ignition spark. Here a list of things i replaced in the last few month:

      Battery, starter motor, CDI, complete Harnes, Alternator, Magneto, Coils, Spark Plugs, Spark Plug connectors, ignition switch, complete fuel pipes, rebuild the carburator and every rusty screw I can found.

      Everthing is running perfectly, all lights work, neutral light is glowing, starter motor runs smooth. My current method of trying to start is nothing special. Just hit the start button and bikes trying to start the engine. I can do this until the battery is dead, nothing happen.

      Anyone can help me ? I am  hopeless und frustradet.

      here a few impressions of the bike:

       

    • #5435
      ♠️ MARCEL
      Administrator
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      Jan 25, 2021
      @mf448kxn6
      North UK
      GTR

      Hey welcome to the club 🙂

      Let’s try the basics before we get too technical.

      • Can you take out the spark plug and connect it to the HT lead
      • Then place the spark plug on your engine cover BOLT (ground)
      • Avoid rust spots or painted parts.
      • Crank your bike.
        Does coil Front Spark?
        Does coil Rear Spark?

        If yes, to BOTH engines, can you spray carb cleaner inside the airbox ?
        Does it try to start ? (even for 2 seconds)

      Let us know!

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

    • #5485
      Rhino_1990
      Member
      • Topics: 1
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      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      Thank you for you’re advise. I followed your instructions but the bike does not start, even not on carb cleaner / start pilot. So i seperates the carburator from the bike and dissassembled the whole thing. Found out that the new float needle is broke and that the fuel is flooding the whole engine.

      I had my old (original) float needles and will put them in after a fresh new cleaning of the carburator and all other parts. I put everything together during the next week and hope for the best.

      maybe there was too much fuel and it quench the spark. That would explain why it does not run on carb cleaner / start pilot.

      i put the carburator in my ultrasonic cleaner with brand new fluid and it comes out perfectly. maybe there was something else in it that cause problems

       

    • #5498
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      Finally I had time to put everything together. Carburtaor is dry now and stoped flooding the engine. But unfortunately the bike does not start. Doublechecked your advices, but everthing looks fine.

      Any further advices ?

    • #5501
      ♠️ MARCEL
      Administrator
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      @mf448kxn6
      North UK
      GTR

      You said carb is dry.

      Do you know if the fuel pump is working?

      Crank the bike for 5 seconds and see if fuel is shooting out of a hose in to a bucket?

      If yes,

      Carb floats should be 7mm height (when carb is upside down on table)

      If yes, put carb on the bike.

      Crank for 5 seconds.

      Do you see fuel draining out if you open float bowl screws?  rear float? Front float? Both have fuel?

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

    • #5548
      Rhino_1990
      Member
      • Topics: 1
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      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      Maybe my explenation was a bit misleading. With “dry” i mean that the carb has only fuel where it has to be. Fuel pump pumps the fuel in the float chamber and stops when the float level is reached. So it is working absolutely fine. Float level is adjusted to 7mm according to the OEM service manual i used. (Actually Service manual said 17mm, but that is when the carb is in the bike, if it is on table it has ~7mm)

      In the meantime i have done another compression test. And the result is not good. I have only 7,5bar on the back cyclinder and about 6,5 bar in the front. The service limit is at 11,7bar (12 kg/cm2). Standart compression pressure is about 13,7-15,7 bar (14~16 kg/cm2). So it looks like i have to remove the engine and change the piston rings.

      I keep you updated about the project. At the moment it is way to cold in my garage.

       

      Here some pictures of the compression test and a screenshot of the service manual:

       

       

    • #5550
      ♠️ MARCEL
      Administrator
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      @mf448kxn6
      North UK
      GTR

      Oh man, I really hoped it wasn’t the case. Hmm, it could be just a job to change head gaskets. Changing piston rings could be a long job then you also have to make sure the cylinder wall is not scored. So it looks like you have a longer project ahead.
      Do keep us updated cause i would like to see it running so you can go riding as the weather is going to warm up soon 🙂

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

    • #6161
      Rhino_1990
      Member
      • Topics: 1
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      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      # MAYBE DOUBLEPOST SORRY IN ADVANCE, first post a few hours ago with many pictures is still not online #

      Hello together,

      i’m very proud to anounce: the bike is finaly back to life !

      I rebuild and cleaned the engine parts (carbon buildup on pistons and valves) and after putting everthing together I found that the pin that hold the magnet wheel was broken and turned on the crankshaft. So the timing was messed up and the bike was not able to start.

      I’am so happy that the engine is finaly running  😛

      I made a lot of pictures during the engine rebuild, so if you’re interested please have a look.

       

    • #6184
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

    • #6192
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

    • #6197
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

    • #6201
      ♠️ MARCEL
      Administrator
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      @mf448kxn6
      North UK
      GTR

      That’s rare to see that small pin that holds the flywheel rotor snap in half! – wow.  I’ve never seen it when i rebuild engines myself too , they are always intact.

      Well done on the job for bringing the bike back to life , this is good to see.

      I think these pictures will help people know just how much work is involved in stripping an engine down and rebuilding it.   I think you were smart for using new gaskets too!

      Nice work 🙂

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

    • #6176
      Rhino_1990
      Member
      • Topics: 1
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      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

    • #6160
      Rhino_1990
      Member
      • Topics: 1
      • Replies: 9
      Joined:
      Jan 25, 2021
      @rhino1990
      Germany
      Hyosung GT 250 N

      Hello together,

      it’s bin a long time but i can proudly say: The bike is alive  😎

      long story short:

      I’ve got the the engine out, disassamble everything, cleaned all parts from carbon buildup, put new piston rings on, changed all gaskets including cyclinder head and put it all together again. Try to start it and… nothing. Yes you’re not gonna believe it but the error was not in the engine itself. Of course the piston rings were week and the gasket was not in perfect shape. So it was good to change it but maybe the engine had startet when i had found the issue earlier.

       

      The little pin, that hold the magnet wheel, was broken and the wheel was out of allignment on the crankshaft. So it was imposible to start the engine. I made a new pin and after a short push on starter button, the bike came back to life instantly.

       

      Guy’s you’re not gonna believe how happy i was to hear this stupid engine running after so so sooooo much time. And yes, I have to admit, that i got a little tear running down my face ^^

      I made a lot of pictures during the engine rebuild. If you’re interested, please have a look.

       

       

      PS: I actually rebuild the engine way back in April. But after it didn’t started I let it sit there for a few month and revisited the issue last week. Luckely i found this stupid pin ^^

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