♠️ M77
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The GP Sensor would need replacing yes , and also you can find some on eBay UK and eBay USA as these are still good 250cc markets , however be cautious using hyo sites that are blue and white , some riders on this forum have complained a lot resorting to asking PayPal to sort it out for them , unless they have genuine stock issues then they should give you an update.
A GP switch acting fishy does trigger the FI light as the ECU is expecting it and it assess (or guess as best as it can) to ascertain if you are in Neutral or Some other gear before starting, hence EFi versions have 5 contacts on the switch itself , carb models are not suitable as they are hit & miss with some 250 ECU’s – The carb versions have 1 contact point that says “Neutral On” or not , the CDI doen’t doesn’t typically care to sense if you are in Gear 5 or 1 , the EFi ones would , it helps with timings on the rest of the electronics.
Don’t throw it away, it will be a handy backup. Sometimes it does come back to life briefly – Get yourself some “stainless steel” bolts and a fresh O-ring if possible, that gearbox drum behind the sensor chucks a lot of oil!
1st pic is hard to tell but , focus on the ECU and relays first , then go down to the front, less headaches that way actually. Better to work from the back as connectors will be more self explanatory (rear eg = relays , lights , thats it. there is a 2 pin socket next to relay, leave it. and another 4pin socket hiding itself inside a black jacket, ignore)
If not, more pictures will explain it better.2nd image = there is a little white plug with 1 brown and 1 green wire = Engine temp sensor ,
ET sensor sits at the front cylinder head under the throttle body.
Take your time. Also this may help (it is for a 650 but use it as a guide to follow where most parts connect to) (especially where it says “DASH CONNECTIONS”) https://hyoriders.club/forums/topic/wiring-tables/
You noted speedo problems. The link above ^ may verify your harness connectors towards the dash itself.
Then follow the wire colours down your harness, if a dash says “Blue/RED & GREEN” this is 2 wires in a 2-pin plug, it will say fuel gauge, find it on the harness and collect the fuel gauge sensor on the tank
Blue wire from the dash on its own (example) , might say “Neutral” , find it on the harness near the middle so it can reach the N Sensor on the engine, the N Sensor will have 2 wires , the extra wire is for the ECU + Signal to trigger the starting processing (not all 250’s have the same harness or ECU, hence again i can’t always give an easy answer but generally in my experience touching every ECU i got my hands on, DAEWOO is more fussy, very fussy! – excercise patience if you can and do 1 small thing at a 1 as it helps you study too )
I am sure this forum and manualsLIB already have 250 manuals with wiring diagrams at their last pages of the PDF documents. Or even look at the 2008-2009 650GT (It uses a daewoo ECU , only a few of of its parts will work on 250 , so it gets easier to follow. Ie. 650 EFi and 250 EFi early model use the same neutral switch , same clutch switch, the manuals will tell what colour wires they are. Other things like Fan Control, Thermo Switch, etc don’t apply to 250cc as it doesn’t use water cooling.
Hope this helps and good luck!
Have you checked if all the connectors on the bike have water ingress lately?
Also , i could remove the stand switch, inspect the mechanism -> then use contact cleaner to clean the plugs. If the ECU can’t sense it , it won’t start.
Clutch Switch = Same here.
Neutral Switch (under the front sprocket) (don’t pull it out as there is a small spring inside connecting the drum, which is used to track positions , so be wise) and have a bucket as oil will pour our. Top up engine with fresh oil to avoid starving the gearbox. (if 100ml is drained there, then top up 100ml back in)
Ground connections = Black wires or any wires attached to the frame or battery negative.
Starter Switch = Check its PLUG under the fuel tank and open the Starter Switch just to make sure the kill switch contacts are OK. use contact cleaner (loads at halfords)
Starter RELAY Solenoid (Depending on your year GV125-S , it may have “Solenoid Starter + Its own fuse” or just “solenoid” by itself. ) = If these go out, your start button doesn’t work.
Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them. airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies. The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
Okay, but what about the return line? I cant figure it out. Thanks a lot!
have to see what your setup looks like, not all needed and it’s complicated to give a straight answer due to differences between the older and newer pumps and wether the past owners have made modifications to the fuel railing systems such as using a Kemso aftermarket pump or changes to the pressure relief valves on the pumps.
The older black pumps had different pressure ratings and had 1 pipe ==2 pipes ==then single pipe down to the frame == then 2 final pipes to either throttle body where the injector is.
Most of the time , you will see a single hose leaving the pump going to the middle section of the bike frame. It breaks off in to Front Pipe and Rear Pipe after that junction. The 250 is a little less complicated than the 650 thankfully.
You will deal with more air pipes for the throttle bodies , air lines from airbox to Electric Valve Pump which sends even more air down the exhaust pipes (emissions control) (Some bikes out of UK actually have far more , like the american versions for some kind of extra emissions control) , more pipes from either engine cylinder going in to the airbox etc.
Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them.
airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies.
The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
I would stay on the carb system as the FI system on the 25o means you have a lot of EFi parts to stay on top of. Carby is better as its less maintenance and less worry, it’s just better. However, in regards to your cluster , post a picture so we see what it looks like first.
If still wanting to go EFi , check the wiring tables posted by another member in this forum , including this too https://hyoriders.club/fuel_induction_manual/
Also wiring diagrams vary wildly so choose the appropriate manual (on this forum) or ManualsLIB site , Hyosung used 4 different harness on EFI models and 4 different ECU, they use different sensors , it is a big thing to match everything right or you get problems trying to run things properly. Common now is DELPHI ECU (it will say it on the ECU) and uses Delphi Harness (2013-2015) and Delphi V2 harness (different connectors and more fuses) (2016-2019)
Older ECU is not possible anymore (Sentec, Daewoo, etc due those companies not existing anymore) – Hyosung is using Delphi Electronics going forward , you need a tank that accepts EFi pumps too, and possible EFi throttle bodies and a wide array of sensors, EFi air box, injectors , Exhaust should have 2 ports for lambda (Delphi later models) or 1 lambda port for older Delphi or older ECUs .
Though It is hard to comment further until you provide pictures and details of what you have laying on the floor , and possible tell you what system you have.
If the harness has been chopped up , it can be saved but be suspicious! There is a reason carby was better outcome for the bike probably and Regulators are common fault for ALL OEM Hyosung and Chinese Junk ones. Use a TrueMOSFET one such as SHINGDEN Japan , if not , just visit ElectroSport USA , they make an “OK-ish” regulator for the bike.
you will need an OEM GT650R master cylinder (actual one) & clutch perch mount to consider using their thicker adjustable shorty levers you see online. The OEM 125cc master cylinder will not fit 650 levers.
Others resorted to “universal” aliexpress master cylinder and clutch kits but you will be back needing a new clutch cable, Hyosung’s OEM perch stays undefeated , plus i can’t trust £10 master cylinders in emergency braking. So I avoid them.
If not, get OEM Kawasaki ZX9 Front master cylinder and use its shorty brake lever. As for the clutch side, you will study how to implement a hydraulic clutch (custom work & time consuming for a novice to fine tune it) , i’d recommend staying with traditional Hyosung cable setup. Hydro is overkill for 125cc & more maintenance jobs to keep on to off.
Well done! – Looks like the big panic was over! – Be good to definitely spruce up the clutch and yes proper oil too (Motul 300V or Motul 7100!) – Change oil filter again! Gearboxes LOVE clean oil and you will notice a smoother shift initially.
Gear Sensor = Under the front sprocket, be very very careful as oil will come out of there and it is secure by an O-RING , there is also a spring inside too! So you don’t want the spring to fly out.
Get contact cleaner == clean the Socket going to the harness , incase it got oxidized and some signal loss could happen if there was water invasion.
Use Compressed AIR to blow it clean after using Contact Cleaner (NO WD40 please!🔥)
Get also ACF50 (Halfords) – Spray a tiny amount inside the plug , a very tiny amount. this is every biker’s best friend when it comes to anti rust measures and it is electric safe too.
Good luck!
If the bike is older than 4,000 miles old, you could take a look at the clutch basket.
If you squeeze the lever in while idling , if it gets quieter = time for a clutch overhaul , sometimes could add to the gear slipping ?
Drain the oil and use Motul 7100 forever (it is possible the dealer used rubbish trade oil from a barrel in workshop, they don’t really play nice for gearboxes long term) – It just an idea.
Then go for a gentle ride , be slower , and see if gears shift through nicely.
Believe it or not, too much chain slack can mess up smooth gear changes and also remove the sprocket cover , see if the sprocket NUT (front engine) is loose or the washer is loose at all ?
If we can do these things first, come back and let us know if it helps.
Idling issue = Go to halfords and get “WYNNS XTREME FORMULA GOLD PETROL” (ignore redex, and ignore everyone else! They are trash)
Put half a tank of fuel inside and put 1/2 bottle of that formula inside that tank ===> Ride until it is 1 bar of fuel left. See if the idling improves (We are “soft cleaning” everything to do with fuel parts , so WYNNS will run through pump, injectors, fuel lines, then gets burnt away inside pistons and O2 sensors pick up last = This should possibly see if fuel clogging was an issue or not.
Idling at 1600-1800 all day is normal and it cannot be adjusted by you. It is ECU control to keep the engine idling
It would be a good idea to get fresh CR8E plugs and stay with them or get LASER ones (good plugs) = DO NOT use “Iridium IX” plugs as Hyosungs hate them.
IX = Blue Box (Avoid)
LASER = Rainbow box (CR8E LASER)
CR8E = Stock plug (yellow box)Now as you finish riding until 1 bar of fuel left ===> Remove the plugs and show us the pictures here, so we can see if the threads have changed colour and how much. Also pictures of the “inside of the plugs” so we can see a trail of what’s going on (too much air, too much fuel, poor sparking (ie. failing coils or NGK caps which the ECU cannot sense) = The ECU will not tell if the coils are failing or the plug caps have issues , you will find out the hard way when the engine stops altogether or starts firing irregular or shaking (power loss when riding too as running on 1 cylinder etc)
Take your time, I said a lot, but i expect some kind of indepth report back from you so we know every step you took and if it is doing better or not.
If it is something stupid like a loose plug or dodgy clutch bearing or 1 snapped clutch plate (happens but rare) , you will tell us and likely someone else will read this thread to avoid ££££££s of labour at garages who don’t understand Hyosungs at all.
Looks great!
If the headlight is able to be opened, you can replace normal bulb with OSRAM NIGHTBREAKER LASER or PHILIPS XTREME VISION MOTO for bikes if you ride in the dark , the LED’s inside your headlight are for daytime riding anyway.
I like those saddlebags , i will check them out. I tend to use SHAD EU products including tank bag I have now.
Motul 300V is recommended oil. Motul 7100 is also good. I trust these oils more than other brands i’ve tried for more than 20 years.
Motul Cool Factory Line (is the best coolant i have used) , do this when you service the radiator next time. I think it should be 2 years replacement interval (last time i checked!)
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
https://hyoriders.club/forums/topic/rectifier/embed/#?secret=XRZVPeFVeD#?secret=NKSVOrwuC3 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 then Also 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:
Hey good morning! What NGK caps were you referring to? Do you have a link to these? That would greatly help me out, tysm!
They are on this store, so you can see what they look like, and you also tend to find them on most bike garages locally if it is urgent, just screenshot the ones you see as they fit the Hyosung GV
When i heard the video of the bike roaring to life, i was blown away and it is still using ans OEM exhaust, at this point i can 100% say Hyosung did a good replacing that huge bazooka exhaust from previous models to now using twin stylish pipes , i can see they have some bulk in in them to reduce the growling noise! (more noise is good for me but i go deaf faster haha!)
It looks very stylish without changing its original looks too much , I don’t know what else i would change in terms of visual appears , the dashboard with RPM meter was needed 20 years ago! – But hey . they finally did it!
Do you have plans to change anything outside ? – Tail Panniers and Top Box ? I see you got the rack fitted on the rear of the bike
Hi Marcel, It has 90mm jets in the front and 92.5mm jets in the rear.It worked perfectly with the BMC system. But now with the Turbo Kit GP (without a catalytic converter), I have the feeling it’s need more fuel. BR Hakan
Use new CR8E plugs or fully clean your old ones.
Then post 4 pictures here:
2x Front = Side view and center view
Same with rear 2xThen we see if your bike is rich or not
And try this below:
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
Where can I buy one
Look around your local garages for SV650 tunners , they will fabricate or get SV parts to retrofit to your GV and get it certified if your insurance requires it. SV650 and GV650 are different but distant cousins , so it wouldn’t be too much work (hopefully) for your local garage to do it & put it on a dyno to see how much torque its making & HP. Here in UK there limit is about 46 HP for restrictions to qualify, you may have to check your local laws.
thank you. do you know where i can find a restiction plate
You will have to take apart your air box , then look around your throttle area for the restrictions that may be placed.
What if i just revert it back to normal would that be okay? Or should i try inline fuse.
It’s up to you. I do it myself , its just a primitive way to “fast charge” a battery (if i can even say that!) and ensure that the battery still gets the 13.5-14v it wants before the main harness sends it. Inline fuse is needed, incase for whatever reason , the regulator pops, it should blow the inline fuse AND your main bike fuse before it cooks the rest of the bike. Whatever CC hyosung, regulators from China/ ($10 ones) or OEM korea (the tiny silver ones) are its enemy. If you must use an OEM regulator , try to get the updated one (its not perfect , but miles better than the teeny silver ones Hyosung used errornously early on)
Updated one : 32800HN9150
Sometimes it will be BLACK without the extra pig tail harness , either way it will have a part number on it.
If not, get an ElectroSport one (USA) , they have their own website.
If yours is charging well, then ignore this and just get a volt meter to keep a good eye on it 🙂
While i am not in AU , so i am not too familar how they restrict it down there. Here in the UK, they just restrict the throttle bodies so that you can’t do a full throttle twist , usually there is a stopper welded that limits how much the intake opens up. You may have to look at yours to see if that was similar.
GV650 ECU for GV650 only. As GT bikes have their own harness that matches the ECU it comes with and may have 1 or 2 extra sensors more than the GV.
As yours is a DAEWOO or (rarely a Mitsubishi) ECU , you’re locked down to that specific ECU to ensure compatibility (not expecting issues putting a wrong a ECU) – Though some people have tried to shoehorn a GT ECU in to a GV, it was hit / miss . GT650 would also have LAMS done in your country if that was the case too, which leaves us to look at the throttle bodies for restrictions applied.
Tacho = You can study the wiring diagrams uploaded on this site via its service manuals , look for a wire that says TACHO Signal, then get another “standalone” RPM reader , mount it to the handlebar if possible as an additional gauge. Tap in to that aformentioned wire. That’s how I would try to do it personally.
Okay so put a inline fuse on the spliced red wire, attach red to battery and black. Roger i will try that then?
Yes , that’s correct
It was probably done to help the regulator add more juice in the extra lines towards the battery itself before the main-harness feeds it.
The main harness has a red wire from the regulator , that trickles down to the fuse box and then the red wire starts going to the battery and various other places for +12V supply , sometimes it will run to the front of the bike, and then orange wire takes over as the “Switched 12+v” (for when the key is turned on , that orange wire gets active etc.
So i would advise to add an inline-fuse at the END of the red spliced wire –> put a 15A fuse there (but 10A is OK too just for the regulator) –> Then connect red to battery and black to battery.
If you have other pictures just to confirm the connection between the stator plugs and harness looks good (the stator can easily send 90V AC x3 towards the reg and you want the plugs to not have oxidization issues or rust as resistance may go up = extra heat & a soon fried harness!) , feel free to post them. It is a sigh of relief image uploads are working, so now we can see what’s happening!
Correct me if i am wrong on anything i said regarding your bike.
