Forums 🚥 PIT STOP 🔧 Hyosung Technical Help Hyosung GV125 hard to start when cold

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    • #6246
      Eduardo Abreu
      Member
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      Jan 15, 2020
      @scissorhands
      Portugal
      GV125

      Hi!

      I have a Hyosung Aquila GV125 almost 10 years and always i have difficult to start it when it’s cold.

      recentely i bought a few items in here, like iridium spark plugs, NGK coil spark plugs, ignition coil, regulator rectifier and fuel tap, but anyway the symptoms remain.

      i have a video where you can see what i’m talking. Fortunately this time my motorbike turn on on second try, but in many other times not even after four or five tries it starts.

      I hope that someone can give me a clue.

      thank’s anyway!

    • #6256
      Moustache Man
      Member
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      @benjaminsmith
      Colchester
      GV125 2016

      Have no fear! I assume that is the Carby model, based on the white speedo/tach gauges.

      Yeah I had the exact same issue. Even starting from cold on a warm sunny day, it struggled to switch on. I bought mine off a guy who had it sat around for 6 months, riding home on that thing was a nightmare.

      As the carbs are so difficult to access, and you could risk damaging your intake manifolds, it is best to just let the bike run. Use premium fuels if you can, and go to Halfords/any other car/vehicle store and get some fuel additives.

      I personally use REDEX.

      Another tip – get some carb cleaner spray too. Take off the air filter box on the side of the bike (you will only need a screwdriver). Take off the jubilie clip holding the air filter box onto the intake, so you are left with an open intake. Run the bike, give it a bit of throttle and spray the carb cleaner into the open air intake. You should feel the revs increase, then the bike bogs down afterwards. You will find a good routine eventually.

      Another tip as well, adjust your idle screw. Dont adjust it so badly that the revs stay on when you pull the throttle, but adjust it to the maximum before this occurs.

      One final tip – the stock fuel hoses are a bit crap. Cheap rubber, will fray and disintegrate. Get yourself the steel braided hose being sold in the shop here. You will struggle to make it fit, I am running mine without the giant fuel filter but it still runs great.

      Oh one more thing. With the airbox removed, look up at the carbs.

      You should see two tiny little brass screws. These adjust your fuel mixture. Try and get the bike running richer, and just test the screws at different adjustments to see what fits best for you.

      A lot of trial and error, took me hundreds of miles of riding and lots of idling tests to get my bike tuned perfectly, without having to remove the carbs and clean them

    • #6258
      Moustache Man
      Member
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      @benjaminsmith
      Colchester
      GV125 2016

      And another tip! If you plan to leave your bike stored for a while, remember to switch off the fuel tap.

      And if you can, let the engine run until the fuel left in the hoses run dry. The bike should cut out after a few minutes, which will leave the hoses and the carburettors dry for storage. So you can leave the bike for weeks/months without the fuel turning into sludge.

    • #6261
      Eduardo Abreu
      Member
      • Topics: 1
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      @scissorhands
      Portugal
      GV125

      Thank you Moustache Man for your tips.

      the video that i have posted does not show all usual symptoms.

      sometimes it’s more hard to put it running so when it seems it will turn on when push throttle immediately it turns off, and when i put it running i figured that if i press a hose that comes from the left of carby (one that comes in two hoses connected by “T” connector and it ends in nowhere place) the tach rises a little more.

      for now i bought STP products for fuel and for injectors and i will try with that firstly, but let me ask you more.

      both bottles (200ml) tells in instructions to put all content in a full tank of fuel but it say that 200ml is for 50-60lt, so i must do a proportion, right?

      and what do you think i must do in first place? go with fuel additive or injector cleaner additive?

      thanks for your reply again!

    • #6263
      Moustache Man
      Member
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      @benjaminsmith
      Colchester
      GV125 2016

      I have not had the issue with the hoses and the revs, but I understand the problem with using the throttle and the engine cutting out.

      It is clear that you have the fuel to air ratio wrong, where the carburettors are definitely blocked, so you are getting too much air and not enough fuel.

      Our fuel tanks carry 14 Litres, so if the bottle says “one bottle for 50” then put in a quarter or so. No need to measure it precisely, it will not cause harm to your motor.

      Definitely check your idle adjuster.

      Hyosung GV125 AQUILA CUSTOMYou can locate it below the “V-Twin” plastic cover. Run the engine, and twist the black knob anti-clockwise to turn it down a bit, and clockwise to increase it.

      This should help out the engine cutting out when throttle is applied after turning it on.

      Im not too sure what hose you are squeezing, but it is probably the air intake into the carburettor. Which would explain why the tach increases, as you are adjusting the air/fuel mixture into the motor.

      Your best bet is to put the additive in, do a bit of spraying into the air intake, and run the bike. Adjust your throttle cable and eventually the carbs should clear up. The bike will be easier to start.

      Hyosungs are notorious for being sluggish whilst cold. Mine still takes about 5 minutes of riding to catch up to speed.

    • #6266
      Eduardo Abreu
      Member
      • Topics: 1
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      @scissorhands
      Portugal
      GV125

      Once again, thank’s for your reply!

      So for now i have put the fuel additive in proportion and have runned quite a bit with motorcycle and i have noticed that the engine not running quite well with more noise than usual and it seems a bit stuck, not developing as expected between gears.

      i think i must try the other STP product for injectors cleaning too.

       

    • #6274
      Eduardo Abreu
      Member
      • Topics: 1
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      @scissorhands
      Portugal
      GV125

      Hi Moustache Man,

      about the hose i’m squeezing is the end of that you can see in image.

    • #6296
      Moustache Man
      Member
      • Topics: 6
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      @benjaminsmith
      Colchester
      GV125 2016

      I believe that hose is the overflow from the carburettors. It leads out and drips excess fuel onto the chain to act as lubrication. Quite a lot of motorcycles use this system.

      So when you squeeze it shut, the revs increase? That is weird, maybe it creates more pressure within the carbs, allowing for more fuel to pass through, as it only has one option and cannot use the overflow to escape if it builds up too much.

      I am no mechanic, so it is just best to look after the engine, and keep it running/in use. Your best bet is to try and remove the carburettors completely, but you risk damaging the intake manifolds. It would be too expensive to take it to a garage, as they would drop the engine using a jack, charge you for labour, parts and it would cost far too much for what is it worth.

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