♠️ M77
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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
Will you not keep her? She looks stunning! Do like the aggressive brawny MOTO3 vibes it gives out , think its the best looking sports bike hyosung has done and such a damn shame it was shortlived as its bigger sister GT650R was more preferred by most riders and the GT250R funny enough due to them having vtwin motor instead of the GD’s unique single piston 250 motor block. Its definitely faster than a GT250R by a small margin if both bikes are factory untouched (no mods)
As they say, “look after it and it will continue to serve you” , get busy , Spring season right around the corner now 🙂
Check the fuel pump connector even gets a 12v signal, just the fuel pump harness ?
If the pig-tail is dead, remove it, then measure the “main bike harness” itself before it connects to the “sub harness” of the fuel pump. Want to make sure all the wires from the pump down to the ECU is not broken ?
If the pump had a pink wire , i would trace it all the back to the ECU which i assume it should still be the same colour (Hyosung does change wire colors halfway down the harness! so verify with service manual book that has a wiring diagram at the last pages)
Remove the throttle cables and choke cables
Can you rev the bike manually by hand ? and does the RPM needle come down FAST or SLOW or just hang about for a bit then slides down ? etc…
If not sure ===> Go to youtube , upload a video and select it as “UNLISTED” so no one finds it on youtube , then copy the SHARE LINK paste it here.
Dont set it to “private”
This lets us see what is happening, don’t be afraid if its a 3 minute video (10 second videos suck as they dont help make a proper judgement)
Remember = High revs on CV carbs usually means illegal air is still entering or carb is “hunting” for fuel (carb internal issues) or exterior parts (moving cables or choke assembly rail on the carb jammed etc) are still activating the carb to allow more air than usual.
Put mixtures back to 3 Turns out FRONT and 3 + 1/4 Turn out rear, this sets the baseline.
Jetting Tutorial = Click Here
SLIDE needle tutorial = Click Here
Did you change the Intake O-Rings ? They are a big deal than you think, click here
Airbox missing? = Carbs will behave rough, make sure airbox is on and is fully swallowing the front carb as it can peak out.
Get a fresh set of CR8E plugs from halfords . Buy a pack of 4 (2 for test ride) and 2 for emergency
Come back , upload pictures of your plugs on this forum , we gotta see inside the plug and the threads, this will tell us the mixture from idle all the way to 3-4th gear riding down your street.
I said a lot, but please, take your time. 1 thing at a time, so you can see its mood change gradually till you find the culprit.
Grab some vernier calipers and measure the cork plates thickness , do you think they could have been worn down ? Factory plates tend to wear down a bit sooner than OEM
Usually a full clutch EBC kit solves the issue as you get new plates and new metal discs , least this way, you put your faith in a UK brand like EBC to do well for a bit longer.
It does get hole, so its not alarming to see plates and metal discs go dark , but if its all black then yes i would be very worried and the oil being ultra black needed a change!
So time for a new set of clutch springs, plates and the lot?
Also consider MOTUL 7100 oil (it really is a good oil for hot twins) , i trust it more than any other brand for all my various bikes. keep an eye on your engine temps too, if the coolant is 2yrs old or cheap one used by dealer , get yourself MOTUL FACTORY LINE coolant. Best coolant i trust too. Castrol junk products don’t hold a candle to Motul.
Replace the oil filter again, so that old bits dont circulate back in to the bike spoiling up the new oil.
At 5,000 miles , Hyosung says “Inspect or change” clutch at 4,000 miles, so you were right to have a look.
While it is apart, have a good look at the clutch basket and gently shake it to see if you feel any wobble ? and also spin the INSIDE basket to feel for any “grinding” , it should be smooth.
Hope this helps!
Quoting your previous post
”Bike Model = : GD/EXIV/ 250rHi! New to the group after buying/selling hundred of bikes over the years a Hyosung has eventually ended up on my lift.
2017 GD250R/EXIV 250r only 400 miles has not been started in about a year.
First thing I replaced on it was the battery. It cranks slow. Have tested and tried a handful of known good batteries so it is 100% not a battery issue.
have checked nothing else, I will start with frame/engine grounds, starter solenoid and then starter.
any input from other owners? I just want to acknowledge how cool it is this seems to be an active forum. Almost all bike groups have moved to Facebook at this point and I don’t think it’s for the better.”
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Have you considered removing the flywheel to check the condition of the sprag clutch ?
But looks like you fixed it though , gotta love electrics! – Apply some ACF50 and clean wires, incase of oxidization after all the years , did the owner ever ride through a bad storm ?
Daewoo pumps run at a different pressure rating, did you swap the internals of your OLD pump in to the new plastic shell of the new pump ?
And retry? Also if possible , check if there is a 12v pulse coming from the pump wires when you turn the bike on ? (this is what turns the pump on to prime, so its a wire / signal check)
As you had the bike apart, you want to use only dry air , and blow the connectors clean for every plug you find on the bike. I would not even think twice to put liquids near the ecu ,as you said, you would have to go in hell to even find another Daewoo ECU again, so i too hope it is not that either.
Check this out
Your will see it by your cylinder heads towards the radiator unless it got relocated by previous owners.
Also browse this forum again in the Technical section, and where it says MANUALS, get the 650 version for a service manual, it will go in to detail about troubleshooting temperature issues of the bike or to diagnose the cooling system , it can also show you readings you should get from your meter when testing cooling sensors such as THERMO FAN SWITCH, Radiator Sensor (aka Temp Sensor) , Engine Temp Sensor – And see if you can report back your findings.
They don’t want to touch the bikes? That’s silly, but little do they know Hyosung was partly responsible for Suzuki’s early days as they made parts for them and helped make the SV650 distant cousin!
You will do a better job than them, you got this!
If you struggle, just add photos in your next comments!
Sorry that I did not upload the rest of the manuals for the 250 , i will get it done but in the meantime, go to ManualsLIB website and search for 2016-2017 instead as this was the most common year for delphi model 250cc bikes.
Heat generally is the enemy of electronics , have a look at your coils and caps.
The plugs will tell you if your injectors are doing OK or the ignition parts (coil , caps are going funny – caps more likely than a coil but both can take each other out)
Fuel Pump = Open the tank when you get free time , drain fuel and inspect the strainer of your fuel pump , hopefully it doesnt scream “needs replacing” incase the pump is not drawing as much fuel as efficient due to a clogged sponge (strainer/filter)
In your country, get this bottle (or similar) but avoid REDEX please:
Pour 2x bottles in the tank (all of it) , ride with 1/2 of normal petrol in the tank , what we want to do here is see if the cleaner will do its job from the pump, injectors, fuel lines , etc and report back to see if the mood has changed ?
Slow Riding = Check your thermostat, it might not be opening/closing properly or not at all , and depending how old the coolant is, flush the system and replace with Motul Factory Line coolant (my personal favourite) , as Hyosungs generally like motul products.
If it is due for oil change, try Motul 7100 (Best oil for hot twins)
Notice I did not give a specific answer , as if i said thermostat , i could be wrong when the bike was screaming about a faulty ignition coil, so its better to do a process of elimination.
Yes, because the woodruff key is needed to lock the rotor. You can feel how heavy it is don’t you!
So if it was missing or broken, you would also have “ROUGH” running as its not spinning properly which could eventually lead to a catastrophic failure.
Make sure the NUT is good otherwise get a new serrated nut that or metal-lock insert nut and use RED LOCTITE on the threads after replacing the woodruff key.
Any Hyosung 250 will have the same size or message local breakers for a much quicker acquisition of that part. Get a spare engine if you have to and its a good backup to have for the future 🙂
Hello admin, I don’t mean to disturb. Just want to check in but I haven’t heard from you. Thank you
You have been replied via email.
RegardsGot my eye on it. Good shout! – Might come in handy when i do another GV Chopper job
What rear light is that?
From the bright red it was , i could say the black/silver theme could work. I tend to like my bikes black as sleepers or red if i want to turn heads but now i am set on black! Easier to hide an odd scratch i may cause with my keys!
It looks 100% better with the backrest / sissy bar 👍
Hi Marcel, it was the front cylinder. I tested the cap, it seemed to be working intermittently if that’s possible? Anyway I had another lying around and fixed it. I will change them to ngk soon.
Switching to NGK is a wise move indeed.
Delphi ECU, that’s good. It should be a little easier, so send an email (click here) with your address and i will spend sometime this week to look for it in the UK (where I am) and hopefully we have some news
