♠️ M77
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I dont have those at hand as its not something i keep on file, but hopefully someone else does. Though, try to look for a crashed 250cc and ask the seller for the ISC unit, so you can double check but also clean your contacts (every plug on the bike including the ECU socket) incase of oxidized pins affecting ohm readings or water ingress found ?
Just an idea!
Tak ale pomiaru dokonałem na zdemontowanej panewce co przekłamało pomiar
The forum doesn’t auto translate sadly , you would have to repeat what you said in English, sorry about this!
it could be possible you have sticky slides that wont go above a certain RPM
Have you tried this mod below?
[How to Tutorial] Adjust Carb Slide Needle (Tuning) Hyosung GV250 GV125 GT GT125R GT250R
Least you want to investigate the needles are also not getting jammed inside the Needle_JET tube (brass) , as the more revs you need, the higher the slide must lift for air passage and fuel to leave the main jets.
Not unless the the skeleton of the carb itself , needs compressed air (again yes)
This is the closest video that explains what part of the carb is activated and gives you more pointers to look for
(Video is only viewable on youtube, due to the uploader making it that way)
have you measured your old parts first ? it would be easier.
Nice work Nigel , who would have thought! – Another reason why we sell appropriate sized filters for the GV125 fuel line kits with a good flow rate.
Keep an eye on her and take good care of it, we’re right on the riding season , I can’t wait to take my babies out, after a LONG depressing grey UK winter lol
I hate to be the legend that upsets you but slowly , investigate the stator (drain oil first) – I believe it would be a good idea to get a new good stator.
Also replace that regulator. never trust a regulator that is not a real japan mosfet shingden on EFI bikes because there is too many sensors that depend on a very stable voltage.
Stator = I had a 3 customer bikes in the last few years where stators where the reason bikes did not cold start properly and i had to replace everything else on the bike, i did not realize the stator was fault.
Bike 1 & Bike 2 = Wrong stator fitted.
Bike 3 = Pulse sensor went haywire.A carb model will get away with a bad stator and bad regulator for a while (in limp mode) as it’s just only worried about a CDI unit.
So yeah, lets go to the stator and regulator unit. Keep your old one for purely emergencies but i doubt you will even need to worry about it as a true mosfet shingden regulator will last years and years and years , I still have the same one my bigger GV EFi model. Everyone knows getting a Daewoo ECU for the GV650/GV250 is like going to war! No gold to be found for 99% of the earth. The regulator was needed to be upgraded even with an inline fuse to avoid electrical spikes to it.
Bike wont start without a stator anyways , it’s the 1st object the bike looks for before triggering anything else. If it starts when warm , but refuses after its cold , check how much battery has drained (if 12.9V in the morning , then check overnight how much voltage was lost)
Get your mechanic to do a “LOAD” test on the battery too using a special Yuasa Analyzer (usually mechanics or garages keep this)
& yes , Hyosungs have a character of their own! Must be a Korean thing!
Does it spark well when its ice cold for hours ? Check your coils if possible ?
To start the bike we need 3 things = Stator Signal (crank spinning) , Injectors firing and ignition coils firing the plugs nice and bright
I would be suspicious of the stator ? It is easy to put the wrong one too or that the pulse sensor seems to hate the cold (ECU thinks dead signal recieved = cut sparks)
Your wobbling = Find out what cable wires are moving and check them (eg ? Clutch Switch sensor, KillSwitch Plug under air box could be covered in crud/dirt ?)
Roger, topic closed.
Continuing the conversation here
From your google drive image , 2_1 , 2_1 ,2_1 in that sequence is = Intake air temperature sensor
This is the sensor on the airbox itself. To diagnose this, go back to the service manual and search “C21” code, there is a diagram they wrote on how to test this.
Also it would be very wise to get compressed air (air only!) and blow every connector on the bike clean, so you have to find a day where you strip the bike down and take your time, remember where everything was or label the plugs if you want.
No liquid cleaners on the ECU sockets whatsoever, that is the most sensitive and most infamous ECU that plagued the early Daewoo GV250 models, so much that Hyosung moved on and switched to the Delphi Electronics.
So look after that ECU like your life depends on it and if you have to , buy a few fork gaiters , yes fork gaiters , and use them to hide plugs away from exposures of the road / rain / salt etc..
Use a “tiny” drop of contact cleaner on every plug you find EXCEPT the ECU plug! – Leave to dry overnight.
Get a can of “ACF50” , apply this in every plug you can find , EXCEPT the ECU plug again. (This is oxidization protection / anti rust measure)
Hopefully we get some progress ? keep us posted!
Check this out, there is an actual pin out for the 3 plug CDI unit
Needing a little help with my current project (+GT125 CDI PIN OUT)
See if that lines up with your bike, otherwise as you said, if it runs , i would not touch the CDI again haha.
Get a fresh set of CR8E from halfords , those plugs. Do not use “IX Blue Box” iridium plugs as Hyosungs are not keen on them (Hence we use stock ones or LASER type plugs) but i am digressing.
Go for a short ride with new plugs. Come back. Take many pictures. Upload them to this forum so we can see , if its electrical issues we will tell. Also label with plug is front or rear.
If not, upload pictures to GoogleDrive/OneDrive and make a “public” folder called “hyoforums” or something else , paste the share link here , whichever way is easier for you.
I hope also the throttle slides (diaphragms) have not got sticky , if they did, they will cap the speed the bike rolls at . They need to lift fully and smoothly to allow more fuel . the faster you go.
As long as it has the original AirBox on it, the K&N catridge + updated mains should be fine. Main Jets only activate fully when on the road.
If in the garage / stand still traffic, its your pilot jets that do the work. See what happens when you do a deeper dive over the weekend.
Good luck!
Hmmm, try ebay UK or ebay EU for “GV125” CDI as they use 6 pins but if possible at all , can i ask why the need to replace the CDI if the bike is working as it is ?
Also, upload a current picture of your CDI so we can see the underside of it, then i may see if other Hyosungs fit that you may scour a used one for cheaper ?
Regards
Did you change the Pilot Jets ? (if yes they should stay at Size 20 forever) and is the airbox ON ? They don’t really like to run without the OEM airbox attached to it.
(Weird upside down CV carb physics)It sounds silly to say this but have you checked the sparks on both cylinders?
Also, remove the intake pipes going to the cylinders and check their o-rings. Just even a tiniest leak from there runs the whole bike as they are very fussy when it comes to that , its easy to lose vacuum without realizing it. The previous owner may not have touched them since it was new, but enough heat cycles over the years will necessitate the replacement of those O-Rings.
Find something like this exactly:
Spray the inside the AIR FILTER CATRIDGE or the AIRBOX INSIDE = About 3 seconds worth of spraying. Then fit everything back in nicely including the tank.
Do this outside the garage if possible as this stuff can light up in flames if anyone is smoking near you or weird sparks happening from electric sockets in garage, etc…. I can’t stress this enough.
Put the bike on Full Choke. Start it and let it scream for 2 mins on choke, make sure it has fresh new fuel.
Slowly wind down the choke lever and adjust the Idle Screw Tickover at the same time until it revs around 1500 rpm cold (it will rise to 1800 max when its hot which is maximum recommended) although Hyosung says 1500 max all day , i find 1800-1700 sweet enough. Don’t exceed 1800 rpm as you will be very slowly cooking pistons idling in hot traffic.
See if these tips helped ?
Very helpful insight! – Nice work! – I edited the title , so that people can find it if they ran in to the same issue and need an easier fix than hunting around for the OEM replacement.
From your video , it says 2 flashes then 1 single flash = 2 _pause_1 is that right ?
Also what ECU is it using right now as 2013-2014 was the final year some countries were still using the infamous DAEWOO ECU and 2012 is the real year Hyosung started using a DELPHI ECUThen also try to unplug the battery for 24hrs (or overnight) then plug it back in, Turn the Key On. Dont start the bike. But flick the Kill Switch 3 times quickly , this should trigger a flashing sequence.
If not, it probably will flash when you ride (meaning a problem happened while riding)
Do you also get flashing red lights when riding yourself even if its brief ?
Go to halfords and get “WYNNS FORMULA GOLD” (dont touch redex whatsoever) , pour the entire bottle inside the tank.
Make sure to drain the OLD fuel first as it has probably gone stale and the carbs inside may have old deposits clogging the jets
Use E5 fuel only and the entire bottle of that Formula Gold , ride as much as you can until you get about 2 bars of fuel drop down, this should allow the Formula Gold to “Soft Clean” the entire fuel system and probably move any debris or old stale fuel varnish inside the jets, we expect the bike to respond better.
Let us know if that improves bit by bit ? then it was the fueling system.
It would be a good time to look at your spark plugs.
If unsure, upload pictures of your spark plugs so we can see the threads and the center cone, we shall know how the fueling is by reading the plugs after a long run (at lower speeds so you don’t stall if the carb still needs cleaning out/ cobwebs blown out!)
Both holes = Fuel overflow & Breather , extra long hoses until they are about 12 inches (ish) close to the road surface.
Its okay ,
If you haven’t , you can get a good quality japan (any brand based in Japan) X Ring chain , start with 120 links then cut to fit, it lasts as long as you maintain it, we dont have an exact figure as its hard to keep track of everyone’s mileage as they all use varying qualities of the chain.
Rear sprocket, a fresh one is a good idea and always replace the front, the front sprocket being too worn down will eventually damage the shaft, and if you do replace the “Locking Tab” washer (i can’t stress this part enough) – If the lock tab washer was to rattle even slightly or be slightly worn on its splines, the nut will shoot out of the sprocket cover and watch the front sprocket make a hole in the engine. Seen it all in the UK where riders beg for replacement rare engines. better safe than sorry is to replace everything and torque well.
Use this tutorial as a guide
[How to Tutorial] Upgrade 520 chain & sprocket kit on GV125-S EFi (GV125 S 2019+ Models)
ignore that it is its smaller 125cc sister using a custom chain conversion but the principal is the same.
Riding to 10,000 rpm all day is the safe limit. I would not go any higher. If you don’t care about acceleration and use the freeways, then use a 15T (PBR in USA should be making them , i am not sure , as i just use my own local supply chain)
If its made in CHINA , DO NOT bother installing the sprocket, you will loose the engine! – Japan, Thailand (JT) (Some small Hondas are made in Thailand), EU, USA only.
Motul C2 lube is my Go to chain lube! Or use Scottoiler if you want something sophisticated (check youtube for any bike using it)
