Hyosung Aquila GV 125S running problem

[Luka]

Hello,

I have Hyosung Aquila GV 125 S 2020 with 4000 miles.

My problem is, that when bike warms up it slowly cuts out on idle. When I start cold engine runs fine like nothig happend, and after 3 minutes bike starts to behave strange and it stops running on idle. If I hold the throttle bike runs, but it might feel like it gets lack of fuel or something (it feels like it is choking when k try to rev it).

Can you please help me what could be the problem?

I found a video on youtube which looks similar problem to mine just that mine cuts out after 20 second of running on idle. Also when it is warm idle doesnt sound stable. https://youtube.com/shorts/rfp93L-VQBs?si=3yWQmyRqNA0vlq56

 

I will be very gratefull for all the help.

[♠️ M77]

Hey,

The video was posted by a member on our forum here,   anyway,  can you post your own video ?  Also tell us any mods ? service history ? parts replaced ? total miles it has done  (4,000 miles you said and no more since then?) ?

In the meantime,  take a look at this topic below and tell us if it fits your situation without us repeating it ? as it turned out for the guy below, it was his ISCV unit.

GV125s idle speed when hot

Also, here is this topic which contained your similar situation (Correct us if we are wrong). (could be ECU being fried by coils or stator or regulator as the guy confirms below)

GV125S-EFI Only sparking on 1 cylinder

[Luka]

Hello, oil change was done everey year and bike was barely used, because it is my mothers bike and she dont ride it often. Spark plugs were changed 9 months ago and done 600miles approx on them. Bike is fully stock.

I have seen this two topics already and I think I dont have same issue. Bike runs on both cylinders and evreything is fine when bike is cold. When it warms up it stops holding the idle. When you turn it on again runs fine for 10 seconds and after that starts to run strange and then it dies.

I will make video tomorrow.

[♠️ M77]

Luka wrote:

I will make video tomorrow.

Quote

Sounds good,  as that’s odd.

[Luka]

Hello,

 

I investigated further today.

Bike it is charging the battery all the time (not stator issue).

I checked the spark and it is on both cylinders.

I have found out that engine runs like new when it is cold and when it heats up starts cutting of on idle.

I had a look on idle solenoid and it is moving. (And if I disconnect it it is still cutting of).

Every time when i start bike again when it cuts off it runs normal for few seconds and then it starts dying slowly.

Bike was stopped cutting off when I disconnected the throttle position sensor (TPS) (bike runs like new), but in this case bike turns on the engine light.

What do you suggest me to do? Could it be the TPS issue?

Could TPS send signal further and problem is somewhere else?

I am sending video. (Bike was running fine on the begining when cold)

[♠️ M77]

Right, bare with me , as this is unique so let’s butt heads on this one shall we?

If your bike was a carb model  (or EFi even) , commonly the sounds of the bike chugging, coughing, then dying right away points to usually:

• HT Caps (Heat is their enemy) and it is an outsourced cheap part, so we use NGK instead.
• Coils  (it is not uncommon, but it does happen actually as the bike heats up)

EFi  model only (your bike) ….extra parts for consideration/investigation

• TPS Sensor  (Throttle position) , sounding like the bike was struggling to find an idle spot.
  If you’re adamant to try replace the TPS,  send us a picture of it (email us).  We will order one for you (Not all Hyos use the same TPS sensor, Hyosung changes them)
• Fuel Pump Wanning = But , i  don’t think it’s the actual pump as the ECU would not start or let alone injectors dry run themselves.
  It could be the “RELAYS” on the bike  (Send us a picture and we may replace them for you) , other relays may be involved in the other places like injectors/lambda sensor
• Lambda Sensor ?   (on the exhaust pipe)  – I doubt it,  but if you’re not sure, you can carefully unscrew it and clean it , put it back in and see what happens.
  If not, send us an email with a picture of the sensor  (it has numbers written on it, code names and the plug) (Hyosung changes plugs)
  Hell even the GV125 EFi has had more than 1 ECU change and more than 1 harness changes (so terminal plugs and sensors may change)
• ET Sensor  (Engine Temperature Sensor)  – This was common on the bigger EFi GV bikes but i believed they fixed it on later updates….however…look for a sensor that is on the engine cylinder itself to read temperature ,  if it is not present on yours , it may just be reading temperature near radiator  (water temp instead)
  The old GV250 models have temp sensors on the front cylinder head (which was reading basically how hot the oil was getting as it was oil cooled with oil flowing around the cylinders anyway)  – Just a thought!
• Take a picture of your plugs and show us ?  (Just to observe how dark the threads are and if the center of the plug is at the right colour or not)
  Plugs can leave a small “trail” of hints as to what’s going on inside the cylinder.  , we might even know which cylinder is cutting/dropping the most.

Update us fella. Sorry for delay.  Had my own day in the workshop fixing a customer GV125 too! – It runs now thankfully but carb model.

[Luka]

Hello,

Thanks for the answer.

I will remove TPS and send you pictures when i have some time. Coils must be okay because when I disconnect TPS bike starts to run okay.

I think it must be TPS, lambda or idle solenoid. But I think it could be TPS overheating because it is too close to the front cylinder.

 

[♠️ M77]

Luka wrote:

Hello, Thanks for the answer. I will remove TPS and send you pictures when i have some time. Coils must be okay because when I disconnect TPS bike starts to run okay. I think it must be TPS, lambda or idle solenoid. But I think it could be TPS overheating because it is too close to the front cylinder.

Quote

Okay no problem , will await TPS pictures, send us an email if you need it replaced.

Contact

[Billy K]

I have exactly the same issue… What are the long-term effects of unplugging the TPS?

[Luka]

Hello in the end the problem was with the spark plug caps/connectors. Apparently when original ones heated they didnt insulate anymore and spark was jumping to cylinder head.

I swaped them with ngk ones and bike runs like new.

[Ale]

Ciao Luca

per caso quando hai avuto questo problema si accendeva la spia del motore ???

[Ale]

Hey sorry I got auto translate on phone

im having same problem but the engine light goes on also did you have the same when that happened???

 

 

[Ale]

Ehi scusa, ho la traduzione automatica sul telefono

Ho lo stesso problema ma si accende anche la spia del motore. Anche tu hai avuto la stessa cosa quando è successo???

 

 

[Luka]

• Hello,  in the end problem was with ignition caps. They didnt insulate enough. As solution i bought NGK spark plug red rscing cable with boots and new spark plugs. After thaz bike was running fine. You can even order same kit from this site.

[Author]

Posts

[Luka]

Hello,

I have Hyosung Aquila GV 125 S 2020 with 4000 miles.

My problem is, that when bike warms up it slowly cuts out on idle. When I start cold engine runs fine like nothig happend, and after 3 minutes bike starts to behave strange and it stops running on idle. If I hold the throttle bike runs, but it might feel like it gets lack of fuel or something (it feels like it is choking when k try to rev it).

Can you please help me what could be the problem?

I found a video on youtube which looks similar problem to mine just that mine cuts out after 20 second of running on idle. Also when it is warm idle doesnt sound stable. https://youtube.com/shorts/rfp93L-VQBs?si=3yWQmyRqNA0vlq56

 

I will be very gratefull for all the help.

[♠️ M77]

Hey,

The video was posted by a member on our forum here,   anyway,  can you post your own video ?  Also tell us any mods ? service history ? parts replaced ? total miles it has done  (4,000 miles you said and no more since then?) ?

In the meantime,  take a look at this topic below and tell us if it fits your situation without us repeating it ? as it turned out for the guy below, it was his ISCV unit.

GV125s idle speed when hot

Also, here is this topic which contained your similar situation (Correct us if we are wrong). (could be ECU being fried by coils or stator or regulator as the guy confirms below)

GV125S-EFI Only sparking on 1 cylinder

[Luka]

Hello, oil change was done everey year and bike was barely used, because it is my mothers bike and she dont ride it often. Spark plugs were changed 9 months ago and done 600miles approx on them. Bike is fully stock.

I have seen this two topics already and I think I dont have same issue. Bike runs on both cylinders and evreything is fine when bike is cold. When it warms up it stops holding the idle. When you turn it on again runs fine for 10 seconds and after that starts to run strange and then it dies.

I will make video tomorrow.

[♠️ M77]

Luka wrote:

I will make video tomorrow.

Quote

Sounds good,  as that’s odd.

[Luka]

Hello,

 

I investigated further today.

Bike it is charging the battery all the time (not stator issue).

I checked the spark and it is on both cylinders.

I have found out that engine runs like new when it is cold and when it heats up starts cutting of on idle.

I had a look on idle solenoid and it is moving. (And if I disconnect it it is still cutting of).

Every time when i start bike again when it cuts off it runs normal for few seconds and then it starts dying slowly.

Bike was stopped cutting off when I disconnected the throttle position sensor (TPS) (bike runs like new), but in this case bike turns on the engine light.

What do you suggest me to do? Could it be the TPS issue?

Could TPS send signal further and problem is somewhere else?

I am sending video. (Bike was running fine on the begining when cold)

[♠️ M77]

Right, bare with me , as this is unique so let’s butt heads on this one shall we?

If your bike was a carb model  (or EFi even) , commonly the sounds of the bike chugging, coughing, then dying right away points to usually:

• HT Caps (Heat is their enemy) and it is an outsourced cheap part, so we use NGK instead.
• Coils  (it is not uncommon, but it does happen actually as the bike heats up)

EFi  model only (your bike) ….extra parts for consideration/investigation

• TPS Sensor  (Throttle position) , sounding like the bike was struggling to find an idle spot.
  If you’re adamant to try replace the TPS,  send us a picture of it (email us).  We will order one for you (Not all Hyos use the same TPS sensor, Hyosung changes them)
• Fuel Pump Wanning = But , i  don’t think it’s the actual pump as the ECU would not start or let alone injectors dry run themselves.
  It could be the “RELAYS” on the bike  (Send us a picture and we may replace them for you) , other relays may be involved in the other places like injectors/lambda sensor
• Lambda Sensor ?   (on the exhaust pipe)  – I doubt it,  but if you’re not sure, you can carefully unscrew it and clean it , put it back in and see what happens.
  If not, send us an email with a picture of the sensor  (it has numbers written on it, code names and the plug) (Hyosung changes plugs)
  Hell even the GV125 EFi has had more than 1 ECU change and more than 1 harness changes (so terminal plugs and sensors may change)
• ET Sensor  (Engine Temperature Sensor)  – This was common on the bigger EFi GV bikes but i believed they fixed it on later updates….however…look for a sensor that is on the engine cylinder itself to read temperature ,  if it is not present on yours , it may just be reading temperature near radiator  (water temp instead)
  The old GV250 models have temp sensors on the front cylinder head (which was reading basically how hot the oil was getting as it was oil cooled with oil flowing around the cylinders anyway)  – Just a thought!
• Take a picture of your plugs and show us ?  (Just to observe how dark the threads are and if the center of the plug is at the right colour or not)
  Plugs can leave a small “trail” of hints as to what’s going on inside the cylinder.  , we might even know which cylinder is cutting/dropping the most.

Update us fella. Sorry for delay.  Had my own day in the workshop fixing a customer GV125 too! – It runs now thankfully but carb model.

[Luka]

Hello,

Thanks for the answer.

I will remove TPS and send you pictures when i have some time. Coils must be okay because when I disconnect TPS bike starts to run okay.

I think it must be TPS, lambda or idle solenoid. But I think it could be TPS overheating because it is too close to the front cylinder.

 

[♠️ M77]

Luka wrote:

Hello, Thanks for the answer. I will remove TPS and send you pictures when i have some time. Coils must be okay because when I disconnect TPS bike starts to run okay. I think it must be TPS, lambda or idle solenoid. But I think it could be TPS overheating because it is too close to the front cylinder.

Quote

Okay no problem , will await TPS pictures, send us an email if you need it replaced.

Contact

[Billy K]

I have exactly the same issue… What are the long-term effects of unplugging the TPS?

[Luka]

Hello in the end the problem was with the spark plug caps/connectors. Apparently when original ones heated they didnt insulate anymore and spark was jumping to cylinder head.

I swaped them with ngk ones and bike runs like new.

[Ale]

Ciao Luca

per caso quando hai avuto questo problema si accendeva la spia del motore ???

[Ale]

Hey sorry I got auto translate on phone

im having same problem but the engine light goes on also did you have the same when that happened???

 

 

[Ale]

Ehi scusa, ho la traduzione automatica sul telefono

Ho lo stesso problema ma si accende anche la spia del motore. Anche tu hai avuto la stessa cosa quando è successo???

 

 

[Luka]

• Hello,  in the end problem was with ignition caps. They didnt insulate enough. As solution i bought NGK spark plug red rscing cable with boots and new spark plugs. After thaz bike was running fine. You can even order same kit from this site.

[Author]

Posts