♠️ M77
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Hey Nicolle, welcome to the site!
Hopefully we can help. Sorry if this is a bunch of questions but it would help narrow things down, so take your time!
– As it’s a 2013 = Does your ECU under the seat say DELPHI or DAEWOO or can you post a picture of it here >?
– What size battery is it and which brand/make ? (Sometimes knock off batteries will drain away fast)
- Does it have any accessories ? (Heated Grips, Alarm, Immobilizer, Trackers etc…that could be on juicing the battery down)
- When you switch on the key , do you hear the fuel tank do any buzzing noise ? (Eg. the sound of the fuel pump priming to start)
If you got the right side of the bike , open its cover under the seat for access to relays , you will see “4 pin” relays that are blue or black inside.
Swap them over
Eg. you see 2x plugs that use the same relays , swap the relays , this way we can see if that changes anything.
Relay 1 = Headlights (4Pins)
Relay 2 = Fuel Pump (4 Pins)If your lights work, remove a relay until the lights don’t work (headlights), then swap the relays around , then hopefully that working relay will switch on your fuel pump.
Also another trick,
CAREFULLY unplug the ECU from the harness , be as gentle as you can.
Get “Contact Cleaner” from any car shop or auto shop
Spray a little bit of contact cleaner inside every single connector you find on the bike, every single one. Just unplug , spray them.Also get a can of “Air Duster” or “Compressed Air in a CAN” , spray inside the connectors to blow everything out and dry it out. Then connect parts back to the bike.
CHE error means communication issue usually to do with dash not sensing the harness or ecu not sensing the harness but sometimes its other parts on the bike.
You can also disassamble the “Red” Kill Switch block at the front gently and remember how the stuff was connected before.
Use contact cleaner to clean the switch out. It is okay to unscrew the buttons out slowly inside the red kill switch , then blast them with contact cleaner & air compressor can , === CHE sometimes can be ignition related (Kill Switch block and Ignition Key wires under the airbox too.)
I hope what i have so far helps ~?
We do also have a “Service Manual” on the forum , if you’re interested in studying the bike further ~? It is below:
[Download] GT GTR 125 250 R Comet Carby & EFi Service Manual & Hyosung Owners Books
Get the one that says “GV250” / EFi , its the last link.
Good luck , and keep us updated & happy belated new years!
Hello Andy, Good to have you here 🙂 & Happy belated new years!
Let’s crack on , so you have the bike , that’s great, perharps can you upload some photos on here ?
– The bike itselfAlso, go to the engine, see the front engine ? –> Now next to the rubber manifold holding the carbs , you will see a date stamped on it.
Take a picture of that engine mfg dateThirdly,
Engine number is directly above the stator casing on the left side of the crank , it will say something like GT125-234568 = I will guestimate the engine’s true age from there (but it would not surprise me if Korea makes engines in random numbers)
We do not need to see your VIN number here on public , thats usually for the GOV to know that anyways.
It may be a little tricky as i’ve seen even 19 plates and 20 plates still get registered after jumping crazy hoops , it is because the laws changed before the covid era where “all bikes” that run on 125cc engines with carbs needed to have registrations done. After 2019 , it meant new bikes being registered had to have fuel injection, CBS or ABS and what not to please Euro4/Euro5 laws in EU, which for some reason UK still obeys them after all that brexit mess, ….weird but whatever…
Moving on, you will eventually get a plate from DVLA , i am sure they probably have an un-used 66-68 plate available or a custom plate assigned to it , in either case , this site is an owners club in the sense its a social platform, we have not had to issue certificates dating the bikes , unless they for specifics of how we should “produce” such certificate ?
Regards
It’s the part arrowed in the pictures above that we talked about, Marcel. Think I’m going to need a new front carb body, if that’s possible!
Send me an email please as usual. I am away for new years but should be back at work this week to check my workshop , i do have some carb bodies but will need to double confirm compatibility for your 250 & the state of them!
Let’s try to avoid spending £500-600 for a new carb with taxes , it’s a lot! However, not Hyosung’s fault, it’s made by Mikuni Japan anyways.
I asked for a picture so that i can see how bad it is and i was praying that your carb can somehow be saved, it can’t go in the bin whatsoever. It’s about to get as rare as Rubber Intake pipes now that the world has gone to Fuel Injectors.
i digress. I am old school. For whatever bike i have, i keep a spare carb to myself or least a full donor bike to myself lol.
Sorry about your day!
Do you have a picture of the bike so we can see what variation of the 250 you have ?
Welcome to the site!
Sorry to keep asking questions Marcel but should there be a hole in this item (white arrow)? You mentioned a very small hole, but I can’t get cleaner or anything through it, or feel where air might come out, and I’m loathe to refit until I’m sure it’s OK.
cof It’s Okay, if someone falls on to this topic , they will be happy for it and for you for getting this far . Ask whatever you like!
Yes there should be a hole there…. how about this ….
Find in your house, garage or some car store . A wire for speakers.
Strip the wire until you see individual copper strands . Get one single strand , make it straight .
Then poke inside that Starting Jet , if its clear, it will literally go deep inside and stop.
Then get a carb cleaner or “air compressor” rattle can with a tiny straw , like this ……
You will hear a nice hiss down the bottom of the carb
or
if using carb cleaner, as before spray the golden jet and you will see fluid come out on the side of the silver collumn it sits on deep inside the carb 🙂-
Use e5 forever. E10 will just ruin everything later even piston rings, as it looses speed as time goes on. = Valve Clearance time & Compression test time. Can’t be avoided. I’d do this first before worrying about the carb, you want the engine proper sound first. get hard figures , don’t trust anyone who doesn’t write it down. Change the oil. (Open your “oil filler cap” near clutch cover, if you smell fuel = change the oil to Motul 7100 , 300v , 5100 or Silkolene Comp 4 , Hyos love these oils) Castrol ? = Run away from it. EGR Blanks are sold on this shop for the engine side. Airbox side = block the hole going to the EGR. EGR is useless these days for carb bikes.
so I will have to take it to a bike mechanic as I don’t have a compression tester or valve clearance tools
Let us know what PSi each cylinder makes when the bike is warm, but please caution that certain garages in UK are not that nice towards hyosungs! – If push comes to shove send us an email and come to west yorkshire , we fix them up!
I do hope your local garage “at least” has fixed older GSX bikes and GS motors before touching a hyo, if they have worked on Daelim Korean bikes aswell, then i may “just” probably have some kind of confidence but if you can, go watch them as they do work on your bike.
Because the carb has orings inside the throttle shaft, choke plunger, valve float seats, there were extra freebies incase you did a total disassemble of the carb to pieces!
In this case, you can just keep them as spares for future. I just throw in as much as i can in the gasket kits.
They look good! They don’t need orings those Size 20 Pilot Jets. Just a very clean hole, as by now you have seen how tiny the center hole is!
(Sorry we can’t use more than Size 20 pilots as even size 25 will make it run very rough and too rich.)
Size 20 will do for now 🙂
“Starting Jet” = Permanent. Must be air compressor as hard as possible as the that permanent jet has an even smaller hole then the pilots.
Funny enough, it is also needed when the bike is running, as heaven forbid the bike stalls mid-way through a journey, it will help you start, it reaches furthest in the float bowl, also has an exit on the sides of it (deep inside the carb)
Here’s a hint,
Get carb cleaner & attach a straw to it (they usually come with one)
Spray inside the “Starting Jet” , you will actually see the carb cleaner squirt out of it deep inside the carb’s silver walls where the “Starting Jet” sits on. Hard to visualize , i know but it will make sense when you try it.
Then you know the starting Jet is not clogged anymore!Oh I forgot to mention that revs didn’t change and engine stopped as soon as throttle touched – not surprising with only one cyl going! Fuel. I have no idea what E5 fuel means. Here in Spain it’s 95 unleaded or 98 octane I use 95
Use RON98 , the more premium the better 🙂
E5 (97+ octane) petrol.Here we have changed from RONS to E’s , so its either E10 (which the hyos hate, old cars hate it, some injected bikes/cars have a love & hate relationship with it)
or we use E5Follow this link below and also read comments in that link for extra insight.
What i say on the link below is the easiest way so far. I’ve tried many other ways , you will destroy the inlets soon , so take it easy!
Here you go, this method on the link below saves your hair and inlets too 😉
[Tutorial] How to Remove & Re-Install the GV125 Carby | GV250 AirBox
Happy holidays!
Use e5 forever. E10 will just ruin everything later even piston rings, as it looses speed as time goes on. = Valve Clearance time & Compression test time. Can’t be avoided. I’d do this first before worrying about the carb, you want the engine proper sound first. get hard figures , don’t trust anyone who doesn’t write it down.
Change the oil. (Open your “oil filler cap” near clutch cover, if you smell fuel = change the oil to Motul 7100 , 300v , 5100 or Silkolene Comp 4 , Hyos love these oils)
Castrol ? = Run away from it.EGR Blanks are sold on this shop for the engine side.
Airbox side = block the hole going to the EGR.
EGR is useless these days for carb bikes.
Have you measured the resistance of the coils (without HT caps attached) both primary and seconday and tell us the figures.
If i think from your numbers the coils are okay, then it would be probably HT caps (if they are stock hyo ones, just replace them with NGK) , the 125s do appreciate the NGK products in this season despite weather , the ngk caps & laser plugs do help the bike start faster and spark even the slightest whiff of fuel coming from the carb
The carb now should be 7mm, i’ve not experienced a hyosung run well on 8 to 9 neither 6mm , it has to be dead on 7mm
If it is 7mm, then check the “float valve” needles actually spring back (has a spring inside) and the tips are super clean & not bent, they control how much fuel comes in the carb in tandem with the floats, some jets can’t reach all that deep in the bowl, so a certain level of fuel should always be present and henceforward the upside down nature of the carbs too (Korea did it this way as its quicker to send fuel to engine) (Downdraft / CV=Constant Velocity , speaking of which , the airbox helps)
You will have to make sure when it runs, there is no air leaks on the manifolds because “O-Rings” sit under them, if they are old or squeezed thin, just replace them. You can test this by spraying all over manifolds to see if revs change.
Hey,
When you twist the throttle and it dies, it means either:
- The “Throttle Slides” are not lifting up to release main jet fuel to combustion chamber as the bike revs up
(Sticky or torn slides even so much as a small rubber rip?) - Spray “Carb Cleaner” on the intake rubber pipes connecting the carbs to the cylinder heads = if revs change, there is a leak there.
- Airbox issue ~? (either the top one or the right side one)
If you have size “20 Pilot Jets” I have sent you , that should be inside the carb already (I assume cleaned from any packaging dust?)
How fresh is the fuel ? (Assuming it is E5 grade or better)
Next time it runs, twist the throttle very very very slowly and see if revs rise up?
Editing my quote below from previous reply as I believe we’re getting somewhere now.
- 8K miles. Good , it is young. Check your V5C logbook to make sure engine number is the same ?
It will need valve clearances doing as it’s done every 4k miles.
Tight valves = hard starts, bogging bike.
Hard to escape it. Only way to fix this is to sort clearances if possible.
Every 125cc motorcycle is like this, 650cc can get away with longer miles between valve checks. - If you are sure the carbs are clean, then ofcourse, it will be shown by how clean the pilot jets are by light shinning through pilots and the slides will lift easily with little drag.
- Big rip on airbox ?
- Any chance the “ORINGS” under the inlets have been replaced by now ? (CLICK HERE) Bad orings and bad inlets = directly affect how the bike runs and how it starts aswell, its loosing / leaking air. (Air VS Fuel (your carbs + fuel tap + pump) VS Sparks (Your coils, regulator, HT Caps, Plugs)
- How handy are you with a multi meter to test electronics on your bike (Easy stuff to do but it helps you know if the issue is fueling or air or electronics that’s holding her back)
What kind of speeds do you get ? How does it finally start (tell us what you did to get it to start eventually?) Do you use E10 ? (I reallllllllllllly hope you only use E5) Let us know!
Welcome to the site and happy holidays!
Can we ask ? (to get some understand of how it came to be)
- Total Miles on it
- When was the last time the carb had an ultrasonic clean?
- Any chance the inlet rubbers under the manifolds have cracks (Spray easy start on them to see if revs change = leaks)
- Any chance the “ORINGS” under the inlets have been replaced by now ? (CLICK HERE)
Bad orings and bad inlets = directly affect how the bike runs and how it starts aswell, its loosing / leaking air.
(Air VS Fuel (your carbs + fuel tap + pump) VS Sparks (Your coils, regulator, HT Caps, Plugs) - How handy are you with a multi meter to test electronics on your bike (Easy stuff to do but it helps you know if the issue is fueling or air or electronics that’s holding her back)
What kind of speeds do you get ? How does it finally start (tell us what you did to get it to start eventually?)
Do you use E10 ? (I reallllllllllllly hope you only use E5)
Let us know!
take a look here;
Intake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
and also
Uprated & Braided Fuel Line + Filter Kit :: Hyosung GV125 & GV250 {Carby Models}
Order anytime now ill dispatch after weds when posties open up
have a good weekend
As per simon 🙂
You likely have an air leak where the o-rings are sitting inside the manifolds , frustrating i know but i would use new o-rings everytime the carb is off the bike they are only a few quid but save a lot of stress later on.Air leaks will make the bike feel like is going up and down between revs when its low and conks out or if revs are high, it gets higher when you ride then it does drop very very slowly when in neutral.
Also check vacuum hoses , if you have EGR on the bike. Delete it off the bike and only block the lines that were feeding the EGR , less stress there If the bike doesn’t have it that’s fine, you’re in luck. Less pipes to deal with.
Though, i pray the “Pilot” jets didn’t suddenly get clogged again from debris coming from the pump/tap/ or old air filter or just generally the airboxes (2 of them) not fully secure.
Keep us posted , im sure Simon will likely beat me to it for further replies, you will be alright 🙂
Have a good weekend break!
Hey,
well done on putting her back together! –
I hope this is true below:- Both jets were clean (pilots)
- Starting jet is clean (the tall one inside the carb that can’t be removed)
- Main Jets are clean
- Every part in the carb was meticulously put together.
- Fuel pipes are connected and fuel tank tap is working
When you crank the bike, you will see the fuel drip inside the clear fuel filter as a hint the engine is now pulling fuel out of the tank
This also means the fuel pump is working and connected well.
Now, this should be a very easy process to start it (I hope!)
- Remove the “Air filter” on the RIGHT SIDE of the bike (That small baby air box that hangs on the right side of the bike)
Open it. - Get this product in your local car shop or bike shop, (or something similar to it)
- One you get it…
- Put your bike in neutral (make sure of it by checking the rear wheel spins free, as rarely but sometimes fake neutrals happen)
- Put your carb in FULL choke mode
Since you have 2 hands ofcourse,
- 1 hand twists the throttle & thumb presses start (twist throttle on and off as fast as you can)
- Hand #2 will be spraying “crazy” amounts of easy start in to the air abox hole (since you removed the filter)
Trust me, if your bike is sparking good, it will INSTANTLY start and scream to 4K revs.
- Now leave it on choke for 5mins screaming.
- Then slowly turn the choke off and watch the “IDLE SCREW” adjuster on the left side of the bike to make sure bike idles at 1500 rpm
The fuel should be E5 only please. No E10 fuel. (if i haven’t mentioned it elsewhere on the forum)
Once the bike is okay , get this bottle below (DO NOT BUY ANYTHING ELSE) … It must be precisely this one as i swear by it,
- Now, if you have HALF a tank of fuel. Do not add more fuel.
- Pour the WHOLE bottle of the Formula Gold above
Go for a short ride but dont be far from home yet, just go around the neighbourhood. See how it feels before venturing out far.
Now the reason for 1/2 tank + full bottle of formula gold, is more like an agressive mixture thats going to make its way down to the ;
- Tap (collect debris)
- Fuel filter (dump debris there)
- Travel to fuel pump , collect debris in the lines..
- to the carb
- Full Throttle will have the main jets & throttle slides fully open to dump any micro debris out of the exhaust while riding the bike.
If all is well, the fuel will go to low level after many miles of riding and the bike should be fully awake at this point 🙂
Oh yes before i forget, put the air filter back nicely once the bike starts from easy start.
Also use Formula gold once every 3-6 months to keep the carbs optimal and fuel system generally clean.
Fresh fuel lines and fresh filter helps a lot.
hope this digest of information helps 🙂
Have a good winter break!
Hey , welcome!
I would say try these first;
- Check chain slack (sometimes it affects gearing while moving) slightly or more.
- Check spark plugs (for colour and show us , and also check it says CR8E only)
- Perharps the clutch plates will need changing to better ones ?
Electrical Test;
- Take a picture of the regulator under the bike and show us even also its plugs , ill see if i can do some kind of regulator upgrade for it if its producing less power for electrics
- Test the regulator when the bike is at 5000 revs , see how much voltage the battery is making
Electrical Test 2 (advanced);
- Probe the 2 pins inside each coil and tell us ohms under 200 ohms.
- Probe 1 pin and the HT wire together and tell us ohms under 40,000 ohms.
- Unscrew HT cap gently anti clockwise and test “ONLY” the HT CAP (these cause spark issues and power problems because it is made in china) = Tell us ohms under 30,000 ohms.
After that connect HT cap to coil properly by screwing it back in to the coil before you start the bike.
- Sometimes it could be a sign of a failing coil (Happens to all Hyosungs, fortunately it is not the end of the world 🙂 …)
Other;
- Check clutch cable ,maybe its pulling the clutch a little bit ? so check cable is fully adjusted well and is not trying to engage the clutch while bike is in neutral.
I hope this helps and let us know your progress. You’ve got this! 🤞
Big mission isnt it ?
Sadly though;
- Crank won’t handle it whatsoever as its already at max capacity trying to spin 2 pistons as it is
- Carb of the 125 probably will handle about 7psi pressure of fuel or max.
- Need injectors and go all efi
- No turbo exists that we know of in UK that can spool over a single 62cc piston
- Too much drama and work for the accomplishment.
- More power , more heat , more cooling needed. the little 5-row oil cooler won’t cut it sadly pal.
Though i have to ask , why the need for 2 turbos on a 125cc? (That i would like to see and i shall hang my head in shame , i’ve thought about this for 10yrs , i just cant find a feasable way to do it without things going wrong, can’t get past the limitations of a 125cc-250cc)
Hence most turbo’d up custom hyosungs are on the GV65o bikes instead, abroad. Rare sight in UK (and if they did, they wouldn’t really brag about it lol)
(Electric taiwan turbos do not work, they rob more energy than it produces sadly)
Thank you for your advice. I will check alignment according to your method over the next few days. One point… you say slack has to be 15mm but the Hyosung manual recommends 30mm!!!
15mm when the bike is in the air (resting on paddock stands), it means the suspension has compressed, so the chain slack reduces.
When the bike has both wheels on the ground and on its side-kick stand , it should be 30mm like most motorcycles 🙂
I will say always check the slack again once its on the ground after tightening things up & dropping the bike down gently away from its paddock stands.
if i made any sense 😀
