Forums 🚥 PiT STOP 🔧 Hyosung Technical Help GT 250 not delivering in low RPMs and problems to startup after a ride

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    • #10892
      RedRobRockin
      Member
      • Topics: 1
      • Replies: 2
      @redrobrockin
      Denmark
      GT250 2008

      Hi everyone, new member here with a ‘new-for-me’ used Hyosung bike.

      Just a bit of background. I am riding for quite some years, and I own a Kawasaki Versys 650 back in my home country. However, I moved abroad and I bought a used Hyosung GT 250 with around 30K kms, as a very cheap way to enter the riding world in this new country and see if it makes sense to import my home bike or go with something different. Also, I thought it would be a nice way to get to know a bit more about the mechanical parts of a motorcycle as this is something I wanted to do for some years and I felt more comfortable messing with a smaller and simpler bike than something new.

      Now let’s focus on the bike itself. It has a long history and is definitely not in great condition. At some point, it was stolen and retrieved, with major issues, and I bought it from a hobbyist who attempted to bring it in good shape. Overall, it rides ok but I have two main issues that I want to dig into.

      The first problem about power delivery in low RPM especially on low gears (1st and 2nd). I always try to keep the bike running for 2-3 minutes before I start my ride which I consider an ok time compared to my other bikes but even then the bike power is cutting out (not sure if this is the correct way to explain it) on the low RPM of 1st and 2nd gear.  I uploaded a video that you can see what I mean (youtube: cold_start). It can clearly be seen around 3:02-3:07 and 3:41-3:44. One minute later, there is not the same issue (4:30-4:40). The warmer the bike gets, it gradually disappears (youtube: warm_acceleration).

      My second problem, which might be somehow related is that when I make a stop and the bike is still warm, it is having a hard time starting up (this is weird as the bike starts perfectly fine when cold). I recorded a video where you can see a bit of its struggle (youtube: startup_warm). It has happened before that the RPMs needle will go all the way up while trying to startup and the bike won’t start.

      Any ideas on where to start? Does it make sense to get my hands dirty or should I just accept that the bike needs some time to warm up and that sometimes I might need to wait for the bike to cool down before I can get back home after a stop? 🙂

      On the good side, I am really impressed by the breaking and generally how much joy a 250 can bring you! Hope to get the small issues fixed and ride it a bit more!

    • #10893
      Simon
      Member
      • Topics: 1
      • Replies: 261
      @syco
      Kent
      Gt250 f1

      Sounds fuel related to me, carbs need ultrasonic cleaning fuel lines, filters checked etc.

      • #10894
        RedRobRockin
        Member
        • Topics: 1
        • Replies: 2
        @redrobrockin
        Denmark
        GT250 2008

        I am not that sure that it is fuel related, as this only occurs when the bike is not warm, and only on low gears. Higher gears with the same (low) RPM don’t seem to behave in the same way, the acceleration is smooth there.

        Also, I am pretty sure my bike is fuel injected as there is no choke, and the instrument is the “newer” type with FI light etc, but I might be wrong as I am only now starting to dive into motorbike maintenance and how they work in general.

    • #10897
      Simon
      Member
      • Topics: 1
      • Replies: 261
      @syco
      Kent
      Gt250 f1

      Didn’t realise it was the fi one, a compression test is the first place to start.

    • #10908
      Simon
      Member
      • Topics: 1
      • Replies: 261
      @syco
      Kent
      Gt250 f1

      I’ve been considering this issue (I own the 250 fi) it’s going to be a process of elimination, first thing the easiest to do is connections unplug & clean all the connections with contact cleaner, there’s several under the tank along side the air box, the fact it’s not throwing any red light says that the ecu thinks everything is OK. Now the sensors regardless of what they do work pretty much on resistance so this controls the the injection time, next is the compression test if that’s OK then a valve check would be next.

    • #10909
      RedRobRockin
      Member
      • Topics: 1
      • Replies: 2
      @redrobrockin
      Denmark
      GT250 2008

      Thanks for the reply Simon, another thing that is bothering me is that under heavy rain the motorcycle misfires and finally turns off ( this happens also when the road is very wet, even if it is not actually raining). So I was already thinking of checking all connections and probably put some electrical tape around them. I will try to find some time to at least clean all connections over the weekend and see if it’s any better.

    • #10910
      Simon
      Member
      • Topics: 1
      • Replies: 261
      @syco
      Kent
      Gt250 f1

      That is definitely going to be the front ht lead/ht cap breaking down. Your model should use the same coils as mine which just so happen to be the suzuki ones fitted to the gs500 1989-2008 & the sv650 1999-2002.

    • #10937
      ♠️ MARCEL
      Admin
      • Topics: 45
      • Replies: 1,899
      @mf448kxn6
      North UK
      GTR

      Good points by Simon!

      Also please make sure the “RUBBER DUST” cover on the front engine head is actually fully sealing the spark plug hole.

      If it’s wet , the water from the front tyre flies to the engine heads, then water tries to invade the spark plug hole  (where your HT cap hides)  -If dust cover is cracked or looks bad, i’d just replace it.

      Speaking of wetness, inspect your air filter too.  Wet air from the filter or plug holes = spark plugs will bog down and bike get the signal to kill sparks off  (hence sudden loss by your bike , forcing you to pull over, risky business in a busy wet day!)

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

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