♠️ M77
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They did the same thing with pre-2017 GV125 and GV250 = Same chassis , same air filter , same coils, but as GV250 got more improved over the years , less parts started to fit GV125 Carb Model (because after 2008-2010 GV250 started to use EFi parts, and we could not even use EFi parts on the GV125 carb model)
Eg. GV250DR / GV250DRA = Air filter does not fit at all , it looks the same but they forced it to only fit 2018+ model and only Hyosung makes it.
GV125S/GV300S were identical in 2019-2021 (for plastics and fuel tank) , but as you found out now, due to newer Euro5+ laws passed in the EU, hyosung is doing GV125R . GV125X , GV125-SS EVO (USD forks) , they started to change little parts inside there and there even engines have newer casings. Injectors in GV300S will not even work on GV125-S , etc …. It starts to get complicated , as you go deeper.
So if you wanted to use a GV300S part, it is safer to go for 2018-2020 models before the 2021/2022 facelift. GV300-SS (GV300SA) definitely has a different style airbox and i can’t confirm yet it fits GV125-S due to throttle bodies ( i need to buy a GV300-SS throttle body to verify this )
They are changing GV125-S / GV300-S too fast for me to keep up lol.
However, don’t expect any power improvements using GV300S air filters, blame the stupid emissions laws in EU
This is the recent facelift 300S (SS / EVO ) – There is also an R model in Israel, looks same as GV125-R in France (Sima Moto is the main EU importer)
IAT = Air intake temperature sensor (for airbox) checks the air inside and reports back to ECU
ET = Engine Temp Sensor , it is on the Front Cylinder Header under the metal manifold.
Service manual would usually tell you where these things are and how to test them properly , the IAT would just need to know OMHS readings not voltage.
(Heat changes the resistance = so ECU would know if the resistance goes up , it means air is less dense as more heat reduces oxygen density)
So i would definitely follow the manual checking sensors 1 by 1 first. Some sensors only need ohms readings. If you applied voltage to them, it fries them and you will need to replace them again.
Cold starts where not an issue, and sometimes when its hot, it dies, then i have to continuously crank to get it going which damaged the starter motor in the end , so replaced the starter motor too and its relay.
You could check the service manual for the EFi models to check resistance levels needed for the coils and make sure your coils match (I can’t confirm what the SV650 ones are as i forgot!)
However Hyosung GV650 carby , GT650 carby & GT250 (some efi early models) did use the Mitsubishi Japan SV650 coils (It will have the Mitsubishi logo imprinted on it)
Some GV25o EFi models used GV650 smaller coils – So Hyosung has been known to interchange coils across all their models as long the specific ECU accepts it.
Speaking of temperature, test your ET sensor , here is a similar topic about it:
If the bike had brand new parts (or used parts from a verified working donor) – you should not have problems. This means now, you will spend some time with your multi-meter to test every single sensor on the bike and verify that it is still spec according to the manual.
Probably not (not 100% sure yet) , as GV300 has 3 different designs now (GV300S, GV300SS, GV300R etc…) and I am currently suspicious that the GV300S may be using larger bore throttle bodies (I haven’t personally taken apart both a GV125-S and GV300-S in my workshop yet , there is more 125s in the UK than there is 300s)
I know 100% that Hyosung is using a newer design air filter now going forward, it is like a flat pancake style filter now.
Why do you ask ?
IMGUR is now officially blocked in the UK 🙁
Is it possible to upload on this site directly (you should be able to see the “add media green/blue button” , if not , let me know and use a site that’s called
https://postimg.ccGlad to hear the GD Exiv is doing well 🙂
Check your coils for resistance and see if your HT Caps are arc-ing (loose sparks out of the plug)
This says its for 125GT but ignore the title, you want to use it as a guide to check resistance of your coils and the stator unit too.
Rectifier – How to Test Stator , Battery , Regulator – GT125R Carby
I once had to replace everything on a 2012 DAEWOO model GV250 and the customer was also stumped, it turned out, despite the stator working, it was the root cause.
How? The resistance was OK for the pulse sensor and stator was charging 70v strong around 4k revs , but as engine got hotter and hotter, it started to die down.
We replaced the stator unit , and it was fine since thenAlso the Daewoo ECU is my most frustrating ECU to work on compared to Delphi or Sentec ones , they absolutely want every single connector on the plug to be free of rust , oxidization, dirt etc. Contact Cleaner is advised.
Do not put liquids on the ECU itself = Use compressed air only. Just the ECU area you have to be extra caution, it only takes 1 wire or 1 pin to ruin the whole thing for good and it is near impossible to get a new Daewoo ECU.
I would deal with the TPS later, as its already idling at 1.5k rpm, although just a minor tweak should make her idle at 1800 rpm (Brand new GV’s idle at 1800rpm straight from the factory, it was the carb models that idle’d lower around 1.5K rpm as mandated by the Hyosung service manual)
Also it helps to get fresh plugs again (CR8E Yellow or LASER Rainbow plugs only) – They don’t like “IX Iridium” plugs.
Also if it has stock plug caps, throw them away, they always let us down , and get yourself NGK caps. Very recommended.
If not , use SV650 1999 caps (ensure your engine hole can still be covered to stop dirt or water going to your plugs!) and use SV650 1999 coils (they are bigger) but made by Mitsubish Japan (get OEM ones) , they may be big, so expect to make room inside your plastic cover under the tank for them.
However, if your HANKUK Korea coils are OK, leave them there and just focus on the HT caps. Generally when the plugs and caps go bad , it takes out the coil with it!
Check this out too:
The ECU needs the temp sensor working, it helps it regulate how much fuel goes in there, if cylinder is hot , it tells ECU send more fuel to stop it going lean condition, and it controls your IAC (idle control valve stepper) when the bike is at idle too. It is not good to bypass it. Hyosung has used a small margin in their ECU map code , it means it can’t compensate too much or it shuts down to protect engine.
So i can’t advise a Bypass but , find in the service manual the highest resistance it takes and max temps (eg. 4,000 ohms at 100*C degrees ) and try to find a similar sensor that has the same readings at 25c, 50c , 75 , 100 etc, if it matches the service manual , then use it. Get your mechanic to match the thread on the engine , eg. OEM sensor takes 11mm threads and uses 1.5 pitch , then get a sensor that matches that.
Otherwise, hunt a damaged Hyosung in your country (crashed bike) , and get its ET sensor from them.
I have not yet found a replacement sensor that uses the tiny connector Hyosung uses. Most sensors for bikes and carbs use big plugs , so Hyosung made it difficult.
I would not cut your wires.
If you find a sensor with a different connector (as long as it matches OEM Ohms & Temps) ==> Get a spare “injector + ET” harness from any 250cc EFI hyosung in your country (GV250 / GT250)
GV650/GD250 use water sensors, so they will not work without making the job extra difficult retrofitting it. Some people tried to put a WTS (Water Temp Sensor) in to 250cc Oil Cooled ET port, they almost damaged the engine, so it is risky and almost not worth it.
GT uses more vacuum hoses due to it having a vacuum petcock, but GV has a manual petcock, only worry about Front & Rear engines sending air to the fuel pump. That’s all you need to worry about.
Now, the other pipes like EGR (if present on the bike,) throw them away, the bike wont miss it , infact it will be glad as those things are parasitic (robs vacuum energy) and block the metal tiny pipes at the engine side and then block the airbox’s extra ports.
(I would doubt it , if it is a genuine 2000 engine it wont have egr ports , thats something added to later 2005+ engines to meat the silly Euro3 laws)
(UK for now doesn’t care so to speak as MOT testers don’t check emissions on carb 125 bikes. Just exhaust loudness that’s all.)More on that here:
How to change Vacuum Lines on Hyosung GT125R GT250R & GT Comet (Air Hose Diagram)
For fuel (liquids) , here is a specific tutorial , follow it exactly.
How to change / upgrade fuel lines & fuel filter on CARBY GV125 & GV250 Diagram
The Carb Float BOWLS = Have extra hoses on them that are basically overflow & drain ==== guide them down towards the road. (if you have V1 carbs)
If you have v2 carbs their overfow & drain pipes will be both on top of carb and bottom of carb ==> guide them down to the road.
If still stuck , post some pictures so we can where you get stuck.
Good luck!
Red and Orange will turn the bike on.
Others are not that important but the ignition lockset will have 4 wires coming out of it, just incase the black/white + red/black wire is needed by the harness (ie. other auxilary parts being turned on. )Test with Orange and Black first and test the bike.
If in doubt or it’s not working, post some pictures here.
thanks for the replies. I will look into those after this. I forgot to mention that the FI light is also on. then I turn on off key 3 times, FI light blinking x10 x1 x1 x8, which I think the error code is 0118. I found out online that error code 0118 is related to WTS (I assume it is same as ETS= engine temperature sensor) Is this also possible cause to my bike problem?
If the ET is fautly , the ECU won’t know how to keep optimal fueling as the heat rises , so it has to sense it. However fortunately, you can always remove the ET , get 2 bowls. Cold water and 50% hot boiled water. Get a mercury thermometer in there to get glass readings
If the cold water says 7C degrees , put the sensor inside , get someone with a meter to help you. your hands hold the sensor down to the water but do not allow the “black part” to touch water as it will corrode the pins!
The 2nd person will get a meter out and switch to 100 ohms ===> sensor says 25.5ohms and manual says around 0-10c sensor should be about 30 ohms . Repeat the same process for the hot bowl. These numbers are not true , I am just guessing, the 250cc service manual will tell you the real numbers to look for.
This way you can verify if the sensor is working according to different temperature or if it is behaving faulty (skippy , jumping numbers etc….) , then yes replace the sensor.
It is also very important to make sure the tiny connector is clean and its plug, if there is a bit of rust / oxidization, it means ECU gets less optimal feedback or zero feedback as the current is not enough for the ECU to sense it.
Just like fuel tank, if the float is at the bottom it could say zero ohms ==> dash board says hey your fuel is empty , and a full tank will have a high float, the fuel sensor will report 250 ohms , dash will say you have full = bars of fuel.
Ohms are very important readings for the ECU for sensor like Temp, Fuel , Coils (Stator) , etc
God forbid , well on a carb motor, that’s got damaged carbs (burst floats etc) and it would mean the oil stinks heavily of fuel when drained and comes out like black water , could be another tale-telle sign .
Injected bikes not so much as injectors stay shut when the bike is OFF , as does the electric pump
Although i would not discount the likelyness of Coolant (Radiator Anti Freeze) or Oil making its way to places it should not (expect a creamy looking oil! – God forbid)
You’re on to something there…. Just hope its nothing major
It sounds stupid, if the bike’s stator casing was hit hard and didn’t break, check inside to make sure the holes where the idler shaft sits is not bent in anyway causing the idler gear to skew a little bit instead of staying purely straight. Spirit levels can be handy if done right!
Me a marvel at the same time 😹
What are the odds! 🙀
Stay warm sir , it’s getting icy these mornings again!
You could do a full compression test first (get the readings and let us know what the pistons said) , then carefully take off the cam chains & take apart the valve head.
if i read correctly? you said it skipped the cams ? – So i suspect (guessing) that there is 1 valve that was hit by the piston , even just a smidge , if the valve has, it will show itself when you remove the valve heads off the bike. Tedious process but its the only way to be sure. You can also do leak-down tests (plenty videos on youtube, sorry i couldn’t make a tutorial on the forum just yet)
If we can be sure the whole engine is 100% checked over and you put new head gaskets on , then we move up to the electric side of things but we cross this bridge until the engine is verified first. Valve Clearances do help also.
Sounds like your TPS needs checking (throttle position sensor) and your Idle Control Valve (idle Stepper Motor) = These help regulate idling on the bike.
Check engine clearances (are valve clearances too tight?) or check engine compression too.
This topic below could help, as it goes in more detail on the EFi system
Check the ECU for any error codes, see the manual below to get error codes or “how many times the Red FI” light will flash, see below:
[Download] GT GTR 125 250 R Comet Carby & EFi Service Manual & Hyosung Owners Books
Sorry to hear that after all the effort , a fall forces you back to the garage to sort it out again! Hopefully its nothing major, forgive me for asking a series of questions , but i will be targeting the crank itself now.
1. Can you spin the flywheel by hand and if you do, do you hear any hiss sounds as thepistons move up and down ?
2. Oil was coming out of the intake rubber pipes ? what do you mean? Not unless the “engine overflow” pipe is connected to the airbox rather than overflowing itself down to the road surface (like most hyosungs do) i know EFI models have their engine outlets / breathers go all in to the airbox.
3. If you had a friend or family member with you , sit on the bike, let them push you down the street and you shift to 2nd gear or 3rd gear , will it bump start at ? (we are bypassing the starter motor to verify the engine doesn’t lockup by itself) ,excercise caution though , it may jerk and shoot forward hard , so being cold and icy , the road conditions may be unsafe for sudden tail spins or braking. Just be wise!The key here is making the crank fully spins by hand when you rotate the flywheel manually in both directions. Just to confirm nothing got misaligned when the impact / shock of the bike falling caused something to rattle (it shouldn’t since it just fell in the grass than a jagged concrete surface, i would be more likely to loose my clutch casing or stator casing if it fell hard on to a sharp rock/boulder)
Beautiful tutorial!!!! Very well explained there sir 💖🚀👍
I will link this to the product page so it gets more coverage.
It is a good shout about the bolts , maybe i will get some stronger ones and stock them too just incase other riders need it too.
Please let me know if you source spares. I’ve only seen hyospares but I’m aware that they’re scammers
We got you , just keep an eye on shop , or send an email if you don’t see the part you want and I will verify if we had any luck in the supply chain.
I will try though!
Rolled her downhill in 2nd gear. I’ll keep looking.
Suspecting Stand , Clutch and RO Sensor but could be all 3 at once , working on getting those myself
Neutral should be fine if you can see gear numbers or the green N sign, if its make sure the plug or wires don’t get damaged , wet season now!
Hmm,
– This appears to be carb related or the bike is being “choked on a leash” for some reason.Can we confirm what size jets are on your bike both Pilots and Mains ?
And turn your mixtures downwards (clockwise until they stop) – — COUNT the number of full turns. It’s important, then go back to how it was.
Ie. Front is 3.5 full turns OUT and Rear is 3.75 (3 and 3/4) turns OUT , so we can assess the mixtures.
Confirm:
– Are pod filters being used?
– Cracks on the rubber pipes holding carbs to engine heads
– new air filter?
– CR8E new plugs (if CR7 or CR9 = bin them) (If “IX” branded plugs = bin them , use stock CR8E or CR8E LASER) and beware of fake NGK’s .Electrical = Do these tests below and report back to this topic with your figures:
Rectifier – How to Test Stator , Battery , Regulator – GT125R Carby
If we get more indepth , we can find out what the bottle neck was.
Engine (last war)
– Compression test
– Leak test (little o-rings inside the rubber pipes can cause all kinds of issues , so advised to get fresh ones)
– Slipping clutch?
– Valve Clearances (too tight = lower speeds) or too loose (lower power)
