♠️ M77
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Hey Steve , send me an email , sorry i saw this late. I am based in the UK, and i have a lot of injectors, throttle bodies , IAPs , MAFs , Lambda Sensors, and what not
I’ve literally stripped a SENTEC 2008 bike that was running well , it is 250cc and i can confirm Sentec sensors will work with bikes with DAEWOO ECU up to 2018
I have also removed a whole harness from a 2008 GT250 Sentec with ECU intact, i can’t sell separately but i can imagine they go for hundreds of dollars due to rarity!
GT wiring harness is hard to use on a GV because you will need GT clocks (speedometer) and custom fixings to fit the speedo to dash , plus some wires may be cut to retrofit rear GV lights but im sure front headlight will plug straight in.
I am digressing…
Did both cylinders even spark bright and what colour ? And was the seller honest that the ECU works well ? No FI lights on your GV ?
Or have you found a way to trick your ECU (as per service manual) to get some kind of stored error codes with the new ECU ?
It’s ALIVEEEEE!!!!!!! (Jim Carrey Voice)
Hey hey hey , get that girl going and you won’t need to spend hundreds of dollars on a carb! – If you must , clean it to the extremes and also use air compressor!
(I love air compressor after chemical baths , i mean i get to really blow every crevice , hole , slot , slit i can find in the carb, its a lot of passages lol)
Thanks so much for your kind answer, Marcel. I would like to receive more feedback, specially by Spanish members. Best regards.
You can search for Alan M on this forum, he rides a GV125 & is very active on this forum. You can send him a PM , he lives in Spain too 🙂
Temp Sensor is not available for a 125cc 2016 plate because it doesn’t use “water radiators” .
It has an oil cooler and Korea saw no need to put a sensor on it. However a 250cc cooler is the engine’s favourite investment as it pro-longs its life (Super hot 125 hyos in summer can be moody at times!)
Based on your second reply
- Regulator is shot. Sounds like it’s not charging the battery
- Get a the stator tested though. (Hyosung says if it’s not making minimum 70v AC on all 3 yellow lines, replace it)
(Search on the site “stator” , for old topics to come up , there some multiple replies made on where myself or Simon explains how to test stators)
or
Download on this site GV650/GT650 service manual and “only” follow the section where it says “How to Test Stator Unit” , ignore everything else in the book as that’s for 650cc but 125cc/650cc have the same readings for stators. (Just 650 is bigger that’s all)
It sounds electrical , if it has a standard regulator (Says Hyosung on it or HANKUK Korea) , then it is advised to replace it with a beefy one.
Searching the keyword “stator” will bring some old topics in this site on where multiple replies were made on how to test the stator unit.
So i’d say , a healthy stator (making 70v minimum at 5k revs) is a must. You can even download the GV650 or GV250 manuals on this page and just go to where it says “how to test stator” and follow what Korea says with a pocket meter.
When you confirm the stator is actually making 70v+ (and is under 0.9 ohm on its 3 wires)
Then replace the regulator.
I keepo saying stator because if it’s failing, a new reg will just get eaten up by it and you will likely need a new battery , just in time for spring 2023 , = Correct size battery & brand is YUASA YTX 14BS and get it from halfords or bike shop. Don’t get batteries online due to fakes or sellers selling very very old stock (cells rot if sat for ages)
…..and the one that did, overfilled my bike too as it turns out, lucky it was a garaging service rather than a running one….
That is just appaling!
Owner’s manuals still exist on the internet, can i shame them?!Hundreds of dollars to get a new carb you sure about that ?
Maybe email me and i’ll reply with some options in the used market too.
Single body (possibly)
Other twin carb set = Too much swearing to tune right, they have never liked other carbs besides what Korea provides them and as such they built the airboxes + intake pipes with the expectation of such carb.
Look at another recent topic on this site , someone has got a GV250 with a single carb and i was like wow! (The extremes the previous owner went to get it going!)
This is a photo of my GV125c 2012 that i’m working on at the minute to get up to proper running condition. This was taken about 2017 before I ended up having to garage her for a while due to life getting in the way. I was a new rider at the time, so i think this counts.
With the parts being sent to you, it will be purring just fine in no time fingers crossed your fine hands will do some good TLC to it!
Here is my 2016 GT250N My first bike, and the bike i have been riding through the cold Scandinavian winter with.In my fav colour too!
Hi guys. Basically I’ve fitted a new battery but won’t start when its cold on the electric start. I can bump start it cold without a problem. Then it starts easily. Can anyone enlighten me to a solution please
If you can answer all 4 , i would have a very good answer for you.
- Standard Regulator ? And what year is your engine?
- Can you go to halfords or bike shop and get a free battery test? (They have “load meters” that actually test the battery & tells them if it needs replacing or not)
- When you press start ===> Does the dash go really dark and the relay clicks loud?
- Long shot, but has this bike every experienced hydrolocking >? (Fuel leaking in to pistons when bike is turned off, then next morning fuel is mixed with oil , and bike is much harder to crank in the morning (which i would NOT ride it, as its a soon seized engine) , i saved this for last….
Here in UK we don’t use LED’s on our hyosung front headlights because there is also MOT Tests (UK GOV wants to make sure bike is road worth every year 3yrs from new) , so the MOT Tester sees LED inside the headlight that needs Halogen bulbs, he will Fail the bike test & issue notice to biker to say “headlight needs fixing to be road approved etc”
Problem is that LED generally is difficult on front headlights because
- as our hyosungs do not have much space inside headlight for LED Cooling fans
- Osram & Philips do not yet make CE Marked & Road Legal LED’s for bike headlights.
Osram & Philips are one of the oldest & trusted bulb makers.
Don’t follow the chinese. - Current bulbs on market, will not shine properly because they cause “glare” and do not spread light properly on the road
So yes they look bright , but can be “annoying” type of brightness. New Audi Cars do it better , as they have headlights made for this.
For indicators,
In my opinion , i like bulb indicators because they can be replaced easy and it’s only 10w , so it’s good for the Hyosung OEM Relay. Also here in UK, 80% of road drivers are crazy idiots, they can’t see LED indicators because they are dimm , but Korea indicators with bulbs definitely shine better.You can use LED Indicators with an Indicator Relay (2pin will work ok on RT125 bike too) , this one here is totally your choice. You can double check with Spain if there is any laws about this but i am not sure as i am not familiar with the spanish vehicle authourities. Let us know.
We have many spanish users registered on this site too.
Welcome to the forum!
i’ve only just got the bike and i haven’t changed the fuel tap, it’s currently in a workshop and they’re looking for a fix
Let us know via email if the workshop needs anything from us but i suppose they should you and report back here their findings (They better do the work right and not treat it like its china scrap)
Good luck!
There is always a silent grateful majority who like tutorials , thats why they keep coming back we even had some mechanics actually tell us the clutch tutorials were helpful to them in the past, we know that most UK garages don’t really want to touch Hyosungs which is a shame!
They run great when its all working well and it shows its mood too.
I am digressing, so let me address your pics now
You can block this pipe, as it goes nowhere. So make sure that side-mounted air filbox doesn’t leak air elsewhere too! 
This actually goes straight to the ground (road), (breather hose)
If it is the hose that’s connected directly to the tank and its far away from the tap so to speak.
That is carb float bowl – overflow to the road.
– If your floats burst / jam = it drains straight out to avoid flooding carb.
– if the bike falls heaven forbid , then it pours all of it out (well most)
By looking at this drain bolt, is there anything else I should be aware of?I see chunks of the flywheel sprocket!
And generally clutch metal shavings, i’d open the clutch cover and make sure all looks well, we do have a clutch tutorial on this site too.Topic closed , as it’s a duplicate and check your other one! ❤
Any pictures please?
Close up ones and also distance yourself away from the bike a little so i can see with a bird eye view but i believe with the 2 tutorials on this site, check your self they are routed well.
Search “Air Vacuum” and “Fuel Line” tutorials.Extra hoses will be a tank overflow that’s directly under the tank away from the tap , also EGR system (bypass it & get the extra blanks we sell at the shop if it needs more! – Some engine have twin EGR system (aka Secondary Air System Korea calls them officially) )
Just make sure the airbox is “blanked” from extra hoses coming out of it to the EGR
Is there anything you can suggest I try with carbs in-situ Marcel?
Check Pilot Jet , it gets clogged very easily too.
Then while carbs and airbox are still on the bike, you can spray EASY START inside the airbox
Disconnect Rear Coil.
See if the engine actually sparks the front cylinder in to life and activate full choke , it should try to get it going. I expect if fuel comes out of the front carb, the plugs must spark it.
Or rear plug will be wet (as it was disconnected from HT coil)
But front will be DRY if its sparking and trying to fire
If its flooding, it will be very wet.
Looking at front and rear plugs will give us much better idea what to do next.
And also as per Alan above suggestion ^
The “starting Jet” really actually deals with starting mainly or fast choke system . It’s the Pilots to keep the bike idling.
You can do this right away to help the bike long term
- Motul 7100 oil (strictly this , nothing else) – Get “10w50” grade instead of 10w40 (10w50 is allowed by hyosung)
Also it takes longer to break down , hence good quality oil i recommend it
Fresh oil filter (always) - Upgrade ignition coils (OEM ones on 125s tend to break down)(Common)
- Upgrade to NGK Caps (Better heat resistors) (OEM ones are made by GOLDEN company in China. Cracks a lot inside.)
- Check to make sure Regulator is 14v from idle. = If no, Korea says replace it right away.
- Check to make sure Regulator is 14v at 5,000 revs = If no, replace it.
Fuel System
Tell us below, first ….- have you replaced the fuel tap under the tank (too common) = No fuel or too slow –> Your carb drains its bowls and bike cuts off.
- Fuel pump – New one is a good idea, no rebuilt kits for it exist yet. = Slow dying pump means its prone to cut outs.
- Upgrade to fuel lines sold at this shop and it’s monstrosity filter
Hint = If the filter is HALF full when you finish riding , tap is doing OK
Hint 2 = If filter is Half-Full at 6pm —–> and at 10pm its emtpy === DO NOT RIDE the bike! (Your floats, pump, etc need check as they allowed fuel in to cylinders
Engine hydrolocks
And soon damaged piston rings with excess heat.
Just too many problems later. - USE E5 ONLY = Sorry for all caps but E10 really is a killer. If you use E5, then well done 😉
Carb System
This monstrosity is happiest when its had an ultrasonic bath and a wizard that’s tuned it properly to the tee. If a mechanic tries to tune a carb by “guessing” , do not pay him & don’t use him again.Sometimes tuning also involves checking float height is 7mm upside down
Carb Rebuild Kits include a float valve that actually has a “spring” on it, which can be dead on OEM floats after many years, hence if there is float issues = soon cut out and stranded.
If in doubt, just get new floats at the shop too & don’t adjust them.
Engine Heat = 100000000% recommended to get a 250cc oil cooler. It will love you for it.
We have more than 10x oil coolers for sale, just send us an email. Some are on ebay under the @Evocrest name with protective grills sold separate.Summer is coming.
Cool down that hot girl 😉
Give it to me straight doc, is it fixable?
Yes sir. It’s not dead yet.
Just remember to put where you find that tip and spring under the bike and carefully rise the bike (jack it up) and check gearbox works
Spin the wheel in neutral then select 1st gear while holding clutch, then try to spin wheel?
Try neutral again , and 2-5th gear to make sure gearbox is OK. As that element with a spring is for gearbox.As for the flywheel. You need to pull the flywheel off (Can get a puller tool for you if need be & ship it) , and also will send “used but complete sprag” clutch system as
I will have the kit (the sprocket & the crucial sprag-one-way bearing unit), i know its somewhere as we just had a donor bike to salvage parts from , so being weekend of rest, i will wait till next week to get it together!If interested , send us an email with exact parts list.
If i am honest , EFi has wayyyyyyy more electronics and more parts to change and the front cylinder head needs a special hole bored in to fit a korea ET sensor in to it.
You have a carby system that’s easier to get it going on road!
If you still have the twin carbs = rebuild it with a repair kit and fresh jets , and ultrasonic clean it, it really works wonders as there would be nothing blocking air and fuel mix in the carb body , even new slides are sold on this shop, i have it all.
Fuel Pump is not a bad idea to replace!
Fuel Tap is not a bad idea to replace either 🙂
out with the old & in with the repair kits / new parts , so to speak.
There is a fan that’s on the oil cooler. I would get rid of it. The oil cooler does the job very well and your climate is not the sahara desert so it will never burn itself , just make sure to use quality ESTER OIL as they really love premium oils. Even the gearbox will feel smoother.
I gotta say, he must have had so much trouble finding the Twin-Carb (OEM & best performing) , the owner had to resort to strange fabrications to make a single carb system.
The “Rubber Intake Pipes” that are on the engine heads are OEM and correct, look after them very well.
Looks like you need
– Twin Carbs (Hyosung GV250/GT250 Carb Type, not fuel injection models)
– GV250 airbox (carb type!) as injection model airbox does not fit.
– GV250 “Large” rubber airbox connecting tube
– GV250 “AIR FILTER” box that hangs on the side of the bike and is more enclosed (No pod filters as hyosungs had them)
– Possible throttle & choke cables if they are not OEM ones. (Carby type) as EFi injected doesn’t fit.Seriously though, big respect to whoever did the work to make it run on a single carb “BUT” he should have just found 2 single mikuni carbs (jap) and fabricate an airbox that accepts a filter and hides under the tank , like most bikes do.
It’s up you which direction you want to head to ?
– GO OEM (Recommended) but costs & time to wait for parts to arrive. (That’s if your local wreckers don’t have it, then i have to go get the stuff from donor bike as such)
or
– Spend lots of time away from the rain , as it doesn’t look like it will survive a rainy day and have to meticulously fine tune the carb to try run 2 engines in harmony.Morning David, only joined the forum recently and just read your post. congrats and well done for the perseverance. Beautiful classic tourer. enjoy!
Welcome 🙂
