Forums 🚥 PIT STOP 🔧 Hyosung Technical Help Bike start’s but revs to 6k after upgrades.

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    • #4974
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, after doing all the upgrades, main jets, new coils and cap’s and carb’s stripped and cleaned new fuel lines and vacuum line everything thing went back on today. The bike wouldn’t start initially and took quite a while for it to start it eventually did. The problem is now that when it starts the revs climb to 5.5/6k and no matter what I do with the idle adjustment it has no effect on it.

      Any ideas?

    • #4975
      ♠️ MARCEL
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      @mf448kxn6
      North UK
      GTR

      Hey,

      Since you took the carb apart; the fuel was drained. It takes a few cranks for the fuel to eventually fill the carb bowls then it starts cause the pilot jets dont reach deep enough to start drinking and idling away. Choke speeds things up.

      Revving to 6k is caused by either of these  = manifold leaks , airbox leaks (both airboxes top and right) , loose intake clamps , leaking vacuum port on manifolds , carb not sitting properly , choke cable stuck (?)

      Check choke is fully disengage BY THE CARB itself , check throttle cable and OPERATE THE SWING GATE (where cable slots in) at the carb by hand after disconnecting throttle line.   if revs go down after cables removed , investigate lines or metal assemblies where cables join to carb.

      Hope that helps.

       

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

    • #4977
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125
      1. Hi Marcel, thanks for the info, I think I must have a leak somewhere. I checked both throttle and choke action before trying to start it and they were both operating perfectly. Will have to investigate the manifolds and vacuum lines 😔

    • #4992
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, I have discovered what the problem was with the bike revving to 6k, the linkage between the two carbs was being fouled by one of the clips on the intake manifold. However after sorting that out I took the bike for a quick ride and was very disappointed, the bike reels exactly the same before doing all the upgrades, new main jets, new coils and plugs etc. The bike feels dead in the lower rev range very little power until the revs get up to about 5000, this is how it was performing prior to changing anything.

      Any ideas or suggestions?

    • #4995
      ♠️ MARCEL
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      @mf448kxn6
      North UK
      GTR

      Check spark plug and put the picture here front and rear so I see how dark or light the white cones are.

      Also poorer running is a result of the following

      • Valve Clearances
      • Carb float must be 7mm (all 4 floats inside)
      • Slide needle too rich / too lean (this is midrange from 2k to 6k revs)
      • exhaust modified ? (Make exit hole / baffle of exhaust size of a 10p british coin or 2.4cm diameter hole at exhaust => the bigger the hole, the flatter it feels, some pressure needs to stay inside)
      • Coils will do their job but we don’t know how strong the CAPS are (stock caps?)
      • Coils also run a little better when your charge system is better (stator&reg + battery)
      • Clean rear pump.
      • Spray intake boots and airbox with carb cleaner => if revs change, you have a leak

      if you change gears or downshift etc, and bike feels delayed in picking up revs etc,  pilot jets are clogged again.   Don’t play with the fuel mixture screws and leave it OEM.

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

    • #4997
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, I checked all float levels when I was cleaning the carb’s, standard exhaust, new NGK cap’s supplied by you, and new battery. Slide needle’s set on third ring as per your tutorial. How do you clean the fuel pump? I’ve only ridden the bike once since doing all the upgrades, hope pilot jet’s aren’t still blocked 😔

      Will take the bike out again tomorrow and check the plugs.

      Thanks.

       

       

    • #4998
      ♠️ MARCEL
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      @mf448kxn6
      North UK
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      You will be surprised how easily clogged the pilots get.    If you still have stock coils , consider investigating em as per original reply above.  Not many people worldwide like the stock Hankuk/Woochang coils.

      We shall see how your plugs are ,  laser ones do burn a little better on a richer setup bike. But again, we shall see before i draw any more conclusions.

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

    • #5000
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, thanks for the reply. I purchased the upgraded coils from you along with the cap’s, new main jet’s, and upgraded fuel lines and filter. I spent a lot of time cleaning the carb’s when I had them out as well as fitting the new main jet’s and adjusting the slider needle’s. It was a nightmare refitting the carb’s and airbox so don’t fancy having to do that all over again.😔

    • #5002
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, thanks for the reply. I purchased the upgraded coils from you along with the cap’s, new main jet’s, and upgraded fuel lines and filter. I spent a lot of time cleaning the carb’s when I had them out as well as fitting the new main jet’s and adjusting the slider needle’s. It was a nightmare refitting the carb’s and airbox so don’t fancy having to do that all over again.😔

      Also after cleaning the carb’s I haven’t ridden the bike as side from trying to start it and around the car park, so can’t believe the pilot jet’s are blocked.😔

    • #5001
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, thanks for the reply. I purchased the upgraded coils from you along with the cap’s, new main jet’s, and upgraded fuel lines and filter. I spent a lot of time cleaning the carb’s when I had them out as well as fitting the new main jet’s and adjusting the slider needle’s. It was a nightmare refitting the carb’s and airbox so don’t fancy having to do that all over again.😔

      Also after cleaning the carb’s I haven’t ridden the bike as side from trying to start it and around the car park, so can’t believe the pilot jet’s are blocked.😔

    • #5020
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, I’ve only got a chance today to have a look at the bike, but I found what the main problem was, it was only firing on the front cylinder! The problem was a simple one, the spade connector on the coil for the rear cylinder had fallen off, it was a very loose fit so I just squeezed it with a pliers. I wish they were all as simple as that 🤣

      However even though the bike is running so much better it has a flat spot between 4k and 5k rpm, any Idea as to what could be causing this. !!!

    • #5022
      ♠️ MARCEL
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      @mf448kxn6
      North UK
      GTR

      However even though the bike is running so much better it has a flat spot between 4k and 5k rpm, any Idea as to what could be causing this. !!!

      Pilot Jets or  Slide Needle too rich / too lean (you want to be in middle or just slightly rich due to having extra grooves compared to a factory needle that only has 3 which means its longer needle than factory) ,

      like before above comments also, i mentioned plug check, you’ve still yet to report that. We have to see it.

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

    • #5023
      Alan McLean
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      @macker
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      Aquila GV125

      I will pull the plugs tomorrow and take a photo of each, hopefully that will throw more light on the problem.👍

    • #5034
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, I seem to have a problem attaching image’s to the post. I pulled the plugs today and took pictures I will send them to you via email if that’s ok. Both plugs look exactly the same the electrodes on both are white, also I took the bike for a short spin and it is running worse than the other day, still the flat spot but now when you blip the throttle it takes a few seconds for it to return back to idle, is this also a symptom of the problem. Also I have no Idea if the mixture screws have been tampered with by the previous owner 😔

    • #5039
      Alan McLean
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      @macker
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      Aquila GV125

      Rear plug

    • #5042
      Alan McLean
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      @macker
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      Aquila GV125

      Front plug

    • #5043
      ♠️ MARCEL
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      @mf448kxn6
      North UK
      GTR

      Yikes!

      The black ring should be brown as milk chocolate.  Its a sign you should check clearances and also see if you can get a pro to check mixture (because me advising what turns to put on mixture is rare unless i have the bike at hand myself and will check if it needs balancing afterwards etc) This is a caution.

      Now the big issue. And ride less until this is resolved. See the both plugs have a WHITE center cone that is almost clean fresh.  Few things come to mind and attack each of them without missing either:

      • Clearances
      • Overheating engine. Check your oil is JASO MA2 grade. And try use Motul Ester or Silkolene Ester. It must say Ester.
      • Air leak or too much air.
      • Air leak via intake Orings
      • Air leak via airboxes (both of them)
      • Is the Rectififer producing 14v at idle?
      • Is the Rectifier producing 14.5-15V at 5k revs?
      • Check stator 2 pin plug under 200 ohms and tell us what it says. (While bike is OFF and ice cold)
      • Check stator 3 pin plug for voltage produced at 5k revs.  ENGINE RUNNING. DO NOT DISCONNECT 2 PIN PLUG. SET METER TO *AC VOLTS*. MEASURE PIN1 AND PIN2 = Volts?
      • Then Pin2 and Pin3
      • Then Pin1 and 3

      Your stator is both ignition and charging system.  your cdi and coils wont run without it or they perform poorly if stator  and rectifier are not in spec.

      Thus will explain if the plugs arent firing hard enough or weirdly.   after all you have new coils ans NGK caps so i will ignore these 2 products.

      Change spark plugs to fresh ones.

      What i said above ^ ; also explains the delayed rpms.

      Delayed rpms and WHITE center of plug is also a sign the carb needs checking on these (again sorry):

      • Check intake manifolds and be VERY VERY GENTLE please. Not made anymore!
      • Slide Needle is too deep inside the carb cause less fuel to come out (lean setting).
      • Float height must be 7mm be sure of it.
      • Jets clogged Pilots and Mains yes. Delayed rpms are also pilots.  white center cone of plug is mains and slide needle or air intake system issue (too much) or electrics as above^.

       

      See the ARCH of the end of plug is almost bright grey colour.  it should be dark brown as a sign that motor isnt overheating or leaning out due to everything i said above ^

       

      In essense. the whole plug should have zero black marks and a FULL milk choc color everywhere inside the white cone or dark-ish brown (oak wood)

      Good luck!

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

    • #5045
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Have you ever felt you should never have something!!!

      1. The plugs are brand new I only put them in when I put everything back on the bike after the upgrades so only done about 5 miles, the original plugs were a chocolate colour when I removed them so that would indicate to me that everything else was ok as regards clearances, oil, stator and rectifier prior to reinstalling carb’s, coils, cap’s and plugs. Would you agree?
      2. But I will check both stator and rectifier reading.

      When you say check airboxes “both ofthem” what do you mean by both of them?

      Should I move the needles down to the fourth groove? You also said the needles are not oem because they have more than three groove’s is that correct?

      Anyone want to buy a GV125 😄😄😄

    • #5046
      ♠️ MARCEL
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      @mf448kxn6
      North UK
      GTR

      My replies should be in purple 🏍

      1. The plugs are brand new I only put them in when I put everything back on the bike after the upgrades so only done about 5 miles, the original plugs were a chocolate colour when I removed them so that would indicate to me that everything else was ok as regards clearances, oil, stator and rectifier prior to reinstalling carb’s, coils, cap’s and plugs. Would you agree?
        If your plugs are new = address the intake and fueling system as i was saying above
        The coils & caps won’t be questioned, they are new or bike wouldn’t start.
        Make sure plug says CR8E on them.

       

      1. But I will check both stator and rectifier reading.
        Good idea, if electrics are all investigated, we won’t suspect them again and you might as well do it as part of a major service & “inspection”  to bike , testing the parts is inspecting (to check if they are still in OEM values after however long you have owned it because most owners understand hyo stators and regs are not great from 125 to 650, we all been there, but its good to keep an eye)

      When you say check airboxes “both ofthem” what do you mean by both of them?
      Both top engine box where it swallows carbs -> check clamps, and missing holes not covered (JUST INCASE you got rid of the EGR , go blank the missing hole to stop unwanted air being sucked in)
      Check vac hoses and block any missing holes for EGR
      Check the airbox that’s holding the filter on the right side of the bike.

      Should I move the needles down to the fourth groove?
      As far out of the carb as possible.  – Test run with that setting.
      SAND paper the plugs until they are clear from black soot (gently!)
      or find ways to clean  your plugs. Then look again after test run.

      You also said the needles are not oem because they have more than three groove’s is that correct?
      OEM is 3 grooves, i’ve cleaned a lot of these hyosung carbs  there is always 3.

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

    • #5057
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, checked stator and rectifier today. Stator appears to be good but think I may have a faulty rectifier, rested on diode mode on multimeter going from positive terminal to there yellow connectors and then reverse going from negative to yellow connectors. These are the readings.

      Positive to yellow :

      1 = 588

      2 = 583

      3 = 586

      Negative to yellow

      1 = 587

      2 = 585

      3= 0

      What’s your opinion on this?

    • #5069
      ♠️ MARCEL
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      @mf448kxn6
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      You should try again and run the 3 yellow stator wires in AC mode while engine is running and unplugged 3  yellow plug.  We need running voltages , check my replies above again on how to test the charge system.

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

    • #5070
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, sorry I’m confused, going into the rectifier I have three yellow wires and a positive and negative wire all in the one block. How can I check the yellow wires unplugged while leaving the positive and negative plugged into the rectifier?

    • #5073
      ♠️ MARCEL
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      @mf448kxn6
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      Go to the stator.

      Follow the wires going up to the main harness.

      Ignore the regulator. Dont disconnect it. Not even its 5 pin solo plug. Leave it.

      The stator has its own 3 PIN yellow plug.

      Disconect AT the bike harness (you will find it as you find out where the stator finally joins the harness.

      Just 3 yellow pin plug.  unhook just that.

      Now start the bike and rev to 5k revs and hold it there.

      Set your meter to AC volts.

      See the yellow 3 pin plug of the STATOR ?  do this.

      Pin 1 and Pin 2 = Put your meter red and black probes in any order.

      Get voltage readings at 5k revs.

      Next…..

      Pin 2 and Pin 3  = what is the voltage?

      Pin 3 and Pin 1 =  what is the voltage?

      Now…

      We have measured across all 3 pins and reply back with 3 separate values.

      Pin1+2=40v / Pin2+3=34.5v / Pin3+1=25.8v  as example.

       

      Set your meter to AC 200 volts or AC500v  (beyond 200AC)

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

    • #5074
      ♠️ MARCEL
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      @mf448kxn6
      North UK
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      Stage 2.

      Turn off the bike.

      Disonnect the stator 2PIN plug (blue and green)

      Set meter to 200 OHMS (not thousands)

      Tell us what it says.

      Do this when engine is COLD (real cold)

      Once you get the figures. Let us know.

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

    • #5075
      ♠️ MARCEL
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      Stage 3 Final.

      Connect all stator plugs back to the main bike harness.

      Start the engine and let her idle at 1800 revs HOT.

      Set your meter to DC 20 Volts (must be DC)

      Go to your battery terminals.

      Measure how many volts is showing at 1800 rpm.

      Do this AGAIN at 5,000 revs.

      Now let us know what it says.
      1. 1800rpm = volts?
      2. 5000 rpm = volts?

      Do all 3 stages as i said above. Ill report back how your charging system is.

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

    • #5077
      Alan McLean
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      @macker
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      Aquila GV125

      Hi Marcel, thank you for the very detailed procedure all very clear now and will do it as soon as possible (raining here 😔) and send you all the readings.

      I have also decided to bite the bullet and remove the carb’s and clean them again, I also want to remove the intake manifolds to inspect them for any cracks/splits.

      Because of this could you send me two new intake manifold “O” rings please. Please use the same delivery address and payment details as before.

      Thanks Marcel for all your help, with your support I will get this sorted.👍

      Alan.

    • #5078
      ♠️ MARCEL
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      Ok, I sent you a PM regarding orings

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

    • #5079
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, just to confirm can you send me the following please.

      Two intake “O” two steel intake clamps and an oil service kit.

      Alan.

    • #5080
      ♠️ MARCEL
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      Hi, it’s in progress. You will get a private message soon.

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

    • #5406
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, Happy New Year to you and I hope you are keeping safe and well.

      • I finally got around to removing the carburettors again today to strip down and clean, the bike has not been run since I changed the main jet’s back in November. But when I started to strip the carb’s today there seemed to be a very slight trace of oil in the carb’s!!!
      • Now I did put a fuel additive in the tank when I did the upgrades (jet’s, fuel filter, fuel lines etc) back in November which I regretted as soon as I had done it so I’m not sure if it’s that that I am seeing.

      What are your thoughts as what it could be, I don’t think it could be ring’s as the bike was running ok before the upgrades and there is only 1,300 Kms on her !!!

    • #5408
      ♠️ MARCEL
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      It should be fine.

      Use LiqyMoly 4T shooter in your tank to soft clean whatever may be inside the lines coming for the tank.

      The additives of the wrong kind can leave a bit of an oil residue.

      Also bare in mind sometimes engine does *blow by gasses* then it leaves a thin layer of oil (when it turns from hot mist to liquid) in the airbox but its normal.  As long as bike operates normally.

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

    • #5411
      Alan McLean
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      @macker
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      Aquila GV125

      Thanks Marcel, that’s what I thought just needed your confirmation. I will have to try and source LiqyMoly 4T here in Spain.

      Thanks again.

    • #5471
      Alan McLean
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      @macker
      Orihuela Spain
      Aquila GV125

      Hi Marcel, just a couple of questions.

      • The petcock on the tank is stuck solid in the off position, tried to move it but it wouldn’t budge didn’t want to force it too much just in case I damaged it. Any suggestions.
      • Can you open the fuel pump to clean it and if so what’s the procedure.

      Thanks, Alan.

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