♠️ M77
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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)
Nice work, hopefully this cures it up and get back to adding fuel to test the bike, do keep an eye the welds so they dont leak again depending how fuel reacts to it. Some of us get steel plates and patch them with permanent welds
Hello,
I do work on customer bikes yes in my workshop, besides selling parts.The stock setup is perfect , as any tooth less on the front or tooth more on the rear is kind of 10% better on take off BUT you lose top speed a lot, they dont like screaming at top revs all day.
Better to lose the heavy monstrosity of the stock exhaust for something better. The only aftermarket exhaust i can recommend is the italian Leo Vince. Just search on Google “LEO VINCE HYOSUNG” and you will see it. Looks really good too! but expensive! , i believe it is on Amazon also.
Welcome Jasper!
Good choice on the GV250 being your first bike, depending on your 2009 model (They can either be carb or EFi injected , and also specify which ECU it has)
2001-2010 = Carbs
2008-2009 = Slow Transition to Injection system using SENTEC ECU
2009 = SENTEC ECU or DAEWOO ECU
2009-2014 = DAEWOO ECU
2014 onwards = DELPHI ECUSo Hyosung has made numerous revisions under the hood, but didn’t change the looks too much.
If unsure , just take a picture of the ECU you see on the battery tray or show us what you can see if its not easily accesible (never know what the last owners have been doing to it)
I could probably advise better on the electric department.
Also , some history of the bike on your next reply would be good? Any reciepts of work? What did they do ? What is the mileage? Did they do clearances etc?
Have a look at the Techinical Section of this forum first => Download the 250 Service manual, have a good read through it, as it can explain a lot of things to look out for maintenance wise, this will let you know if the bike is still up to scratch!
Most of all, enjoy it , ride safe as spring is nearly here. The winter has outstayed its welcome!
Rears are special as they have bigger holes and use plates to lock in and lock out as you have seen on yours.
Here is the front one below, same place you got the ET sensor from:
https://www.ebay.co.uk/itm/255956878875We got the ET sensor and is on its way to you, i will throw something random inside as a freebie (some part in our workshop, we don’t need)
the 10 1 7 1 7 1 10 is actually 10 1 7 1 10 1 7 4 somehow I put an extra 71 in there
10 1 7 1 10 1 7 4 = The closest i can decipher is 10 1 1 7 x 2 = Temp Sensor , so probably still refering to the same part , if the Temp Sensor was not working or oxidized contacts , the ECU won’t know the cylinder temps to adjust injection system , could explain why it runs in “limp” mode to discourage higer revs or die quickly forcing the user to investigate. The good part is that the ECU must stay intact , no liquids near the sockets , just a compressed air in to every ECU pin will help reduce resistance (if the Engine said hey the sensor is 80 ohms at 45 Celcius , that signal going down the plug oxdized , ecu plug oxidized , etc , might read as 120 ohms at the ECU side, it will panic and go a little haywire , also the forum should have a service manual for either GT650 or 250 to check the TPS as that would be key too, there is a diagram for it , it could directly affect what the ECU does next
I could not decipher 1 7 4 , but if you work towards overhauling the parts, while the ECU is disconnected, it should report less errors I am hoping!Good question in regards to AC/DC. It will be DC for the GV as anything AC produced by the stator will go to the regulator anyway, though the pulse trigger on the stator goes directly to the CDI, so I expect that a CDI being pre-programmed to read certain timing pulses as the flywheel spins.
I can’t remember but i strongly suspect we may not get a full output of the AC wires as diameter of the 12 pole stator is different to the EFi 18 pole version. This was experienced on the 650cc where the later models required a full flywheel change as the diameters changed by a few mm!
I think you will surprise us as most riders don’t like go in to the abyss like we do haha , they swap the whole thing and be done with it.
Replace the stator to the older 12-pole version
The EFi 18-pole stators never worked on carby flywheels as they use different timing dots. Next get a GV Harness (carb model GV250) and put carbs.
Your next trouble is to get a carb model GV tank + GV vacuum pump + Tank Tap = there is no way to use the Electric EFi pump inside the EFi tank on a carb model.
This should help hopefully.
There is fuel line diagram tutorial on this forum and another tutorial on how to carefully insert the airbox – I have no advise on running Pod-filters and strange chinese-clones or Keihin USA carbs because it will be a frustrating experience for you, you have to be experienced to do this kind of work and i would rather advise on using the OEM carbs and OEM airbox.
strange. it only seems to let me post when it feels like it. I can write a single line, but most times it tells me your reply cannot be created at this time.
It’s a mess! I intend to sort it out in stages, but you seem to reply OK so far !
light it gives me this: 10 5 10 5 10 1 3 1 10 1 7 1 7 1 10 1 7 4 10 1 3 7 10 5 10 10 10 and it repeats.
Hopefully this is correct as i had to try decipher these numbers in block stages, as the bike is reporting multiple faults at once. These are in order of your numbers but i excluded some as i could decipher them correctly, as number 10 was missing for some of them. Notice that the sequence starts with 10 blinks first.
10 5 10 5 [Idle Speed Control Sensor Faulty] if its 10-5-10-5-10-5-5 this exact blinking sequence , explains the idling issues and running issues, it is the unit that has 3 pipes sucking the airbox and feeding the injector bodies filtered air (kinda needed to for injectors when throttle is shut)
========
10 1 3 1 (O2 Lambda Sensors Front not-user repairable, try to clean them to see what happens unless its a dead dodo)
================
10 1 7 1 7 1 10 Engine Temp Sensor Unit (inside the front cylinder next to throttle body or just very bad contacts – extremely sensetive part due to oxidization of pins – ====================
10 1 3 7 [Rear Exhaust Lambda Sensor]
===============
10 5 10 10 10 [Speed Sensor Faulty = its on your fork leg at the front left of the wheel, could need a strip down and proper clean up or replace it if beyond repair and it repeats.
Hopefully this helps!
Youtube video was handy!
Welcome to the club!
Bare with me to deal with the look of the site , it wont change much on the forum but i will try to make it a bit more simplified than it is now. Your post was edited for you it was a good call!
If you start going through everything properly , then you can start a topic for separate issues as it could be used as future reference for other owners who may have done the same auction deal you did in your country. Hyosung 250cc motorcycles have gone through various revisions, so while it looks the same OUTSIDE , the core engine, electrics have seen many changes as Hyosung was using different sensors, different ECU’s to try manage faults that owners reported until they settled with a Second variation of a Delphi system going forward (250 had carbs, EFi-Sentec, EFi-Daewoo, EFi-Delphi (1st generation) , EFI-Delphi (2nd generation that had a revision of its the harness , stator system etc, ) – You can see why having individual topics could be easier to narrow things down each time (ie. one talks about the pump and the other talks about fairings etc) , or if it helps you, you can make a singular journal style topic where everything falls in to one mega thread.
When i saw Green, i had to look twice as i thought i saw a Ninja 250! – It’s a Hyosung, pretty odd colour on a Hyosung bike. Will you keep that colour? or sleeper black?
Welcome to the club once again, I see that you have now busted through the Registration Gates by yourself, so whatever you did, don’t change haha.
10,000 RPM is a safe limit , but because you are running in the engine, you want to stay around 8k until its about 600 miles run in, so take your time. The benefit is that your have a way stronger chain set as you physically found out, he wont be going back to 428s
The customers who made rave reviews on their bikes had stock exhausts you saw in pictures of the shop OR they used Original Harley Exhaust as quoted above ^ = The GV125 since 2001 (carb model) and currently EFi models (2019+ onwards) still hate random exhausts , so its a matter of trial and error to ensure the right exhaust is not losing “lower bottom torque”
Top speed doesn’t matter if you’re under 50mph , it is the “torque” that matters for quick city sprints or going up hill , the exhaust plays a huge part in it. Some people on facebook will tell you (it is a 125 , who cares) are clearly people you do not want them to service your motor next time.
125s my experience repairing them for customers always preferred a proper exhaust (expensive ones) + a baffle that is about the size of a 10p coin.
if ANY exhaust is as LONG (length) as the OEM Hyosung stock and has about a 10p hole size to exit gas = This seems to be a sweet spot. Europeans are using Harley Exhausts stripped from real harleys (a real harley exhaust will make itself known that it is not a knockoff version you see in china)
The name of the harley exhaust to try is in this thread
Remember, it is a new iron maiden, run her in first and watch the revs gradually settle once he is in top gear. After 600 miles, we should have a service again, then it should behave like everyone else on this shop said , “accelerates quicker off the line , but each gear feels longer ” – This is the balance you want to break out of the 75-80+ mph barrier , Factory speed is 60-65 max at max 12k revs!
Feel free to experiment back on a standard exhaust , as you’re going back to the factory setup with a faster chain thats all. Don’t pay too much attention at top speed, you want to find out does it “pull harder” on stock exhaust or this loud one ? Test the torque first, more speed will come from the bottom low end torque (how much pull it has in gears 1-3 = less struggle to get to top gear.) , don’t be afraid to go between 8k revs and 10k revs
It is OK to rev to 10k rpm in gears 1-3 to build momentum for the bike, then top gear will cruise in lower revs like 8K (kinda pointless to ride at 4-5k revs , its a heavy girl!)
Would be good to add a baffle to it as any 125cc doesn’t like riding without a baffle , then again you will get hard evidence when you take it to a Dyno Shop and they will tell you how much HP was lost using that can vs keeping a standard can vs using a harley factory can (has to be a factory can , not some aftermarket harley can)
Most we know so far on this forum is this thread
