♠️ M77
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Compression-test: 12,5 Bar (F & R) = 175 psi
That’s very very good!
Is this when engine was hot? and both spark plugs were out?Can you wait overnight, wake up in the morning and get service manual, open top valve covers.
Get feeler gauge that is in “.mm” (0.05mm to 0.40mm)And let us know clearances for each valve? Dont do this when engine is warm, it must be overnight cold.
Stator has burnt itself, it does happen.
Can you do the following please?
– Show us the flywheel (for any damage) ? and even the numbers printed on the side of the flywheel.
– DO NOT buy chinese stators on ebay they will NOT work (most of them are hit and miss!) trust me. I own multiple hyosungs & fix customer ones here in north england.
– Can you show us the sensor of stator so i can understand what type it is.
– Can you show us the ECU = Believe me, different ECU’s (There is 4 for GV250 EFi & even the GT has 4 too) require different stators , sometimes “by force” a flywheel that matches is included (Standard KR Motors fashion) , but can still get away using old flyhweel if it matches and keep the new one as back up.Once i have this information , i will read your replies and will also advise you. I made custom orders for EFi including upgrade regulators because i am now officially going to do stator kits for EFi bikes with some custom parts included as one (can’t be split) as a Limited Run basis, that should keep a few more GV250 EFi’s on the road as they are nice bikes to be fair , I like them.
I know you have a GT250cc but remember most of its EFi electronics are robbed from GV250 EFi too.
Perharps its also a good idea to do a thorough look at the bike’s electronics with a meter and service manual, tedious task i know believe me, but least a multimeter can help you check other parts are in spec and not slowly being cooked off (ie ignition coils, ht caps, ET sensor on the engine head, etc)
Keep us posted!
Answered by email , since you sent me an email about it, so will close this topic. But please feel free to make a new topic again if having any other issues with the bike but should be a okay! 🙂
Ride easy now.
What would be the benefit of a booster plug for your GT250 EFi ?
Nice input, i also have a carby GV bike and its harness does not check for clutch switch (incase someone tries to start bike in gear) and no side stand switch connector , this is factory , nothing was cut. It seems later models of GV Korea did not bother adding extra checks thats why the later model of GV carby have 2 plugs for CDI
GT has 3 plugs. I won’t like i did make a mistake many years ago setting off the bike with the stand down lol, i made sure this time i will never forget to check side stand is up before going away.
Good diagram, next time someone has issue with CDI i will also show this topic reply you made showing what each wire does. I knew this already just never found time to make a diagram like you did. Nice job
Yup, China market, would not be surprised if china took some parts from Hyosung and also added inferior copy cat carbs (China will not spend £600 on each bike for Mikuni Japan Carbs) , mind you in china anything can be copied. I just wished they copied the intake pipes as we UK need supplies of them haha.
The green wire from the 250 CDI only works if the 250cc (not 125cc) has 2-wire neutral sensor.
All 125cc have a single wire neutral sensor. So their mod was just wasted cut wire and a placebo effect. Better coils and ignition system like caps / plugs will do a far better job than a CDI cheat (which is really not worth the trouble)
The green wire on the CDI goes straight to the Neutral Sensor Plug
That’s why your 125cc has 2 wires on the neutral sensor plug from the harness , but the ENGINE SENSOR itself has 1 wire coming out of it.
So don’t worry about it.
if the EGR/AIS has been blanked on the engine side, then check under the airbox has been blanked too incase last owner forgot.
Hyosung did away with the ON/OFF Taps on the Comet 125 because owners always left the taps on , and their engines eventually seized to constantly having flooded engines or their carb floats eventually got jammed open as the big tank of fuel is awalys trying to rush through it (incase the pump failed too).
Later Naked 125GT had vacuum taps , and GTR Carby always had it its too awkward to turn the tap off under the fairings , so vacuum tap was installed from the get go. Honestly, the Korea taps work as they should but commonly fail a lot, that’s why i never stock them on the shop.
YZF vs GT = Light frame, it is able to run away quick. A tuned hyo will race past it beyond 88mph indicated (which is the true old gen grey engines did factory) this assumes bike is factory mint and under 1000 miles run in. Old age, neglect of previous owners, bad fuel (eg. E10) , etc will make it run poor. But discussion for another day haha. For now let’s revamp your entire bike to is last nook and cranny down to the engine tappets etc (clearances and compression) will be the last major thing to do (can’t be avoided) , 8 valves it has (most 125 only have 2 or 4 and a single piston)
How well can you work on any motorcycle , ie what is your skill level ?
Can you explain more ?
And can you attach picture of the plugs so we see the sides (threads) and the middle (white center cone)Being FI, did you make any mods to the exhaust or injectors or air filter and what are they (either a picture or show us a product link perharps of the mod changes)
Some Fi bikes can be sketchy on modifications if their sensors can detect that air flow has changed (intake or output/exhaust) the ecu as it is has a small margin of compensation before it leans out
or could just mean the Fi system needs cleaning (as all per above comments) ^
Before we get to the parts, it is still under 1000 miles old, so its very much in the “running in” stages
Around 600 miles , it is mandated for dealers to;
– check valve clearances (must be checked otherwise tight valves or loose ones will have a domino effect on peformance to the engine, carbs, etc..)– Compression Test (very easy) – must be sure the pistons are putting out correct PSI after it has warmed up,
— Warm up engine -> then remove plugs (both of them) –> crank bike for 5 seconds max –> read compression.
Repeat again for rear cylinder tooLet us know the PSi it is doing
Myself and partners here in Yorkshire make CNC pistons which are better quality than ebay ones as true stainless hence warranty on them is lifetime, otherwise we lied. Just refresh your seals or fluid every 2-4yrs (liquids and rubber) – pistons themselves you fit and forget 😉
it could work out cheaper in long as OEM pistons eventually rot, so i make sure my donor bikes don’t have such pistons, i tend to discard them asap unless you only ride in dry days then you will be fine!
I would trust the official Korean engine because the last GV250 was still made in korea called GV250DR – China has relationship with Hyosung Korea, so i would be surprised if Hyosung was involved in the chinese market to allow a china factory to clone their engine for china markets mostly.
As per Simon 🙂
If it says TCTC on the caliper, then yes any hyosung “TCTC” caliper will fit as they are grey coloured.
Just not the “brackets” (different forks , different mounts for different bikes)
If the GV125, has caliper that says “DSG” at the back, then you need a 2001-2004 GT125 Comet caliper that is also “DSG” branded , these are rare as are very very early ones for GV125/GT125 specifically.
GV650 is always grey TCTC until later EFi models used black forks and nissin-style large 4 pot calipers.
Keep us posted on the above comments i mentioned on what to do, as i believe it is also fueling woes. trust me it will show itself to be in a better mood.
Also because revs change , it may be due to crappy orings leaking under the inlets (even if the bolts are tight)
See this link hereIntake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
Very very crucial items.
Also get your self “PUTOLINE RACING GREASE” and soak the orings in them.
Hide the intake holes of your engine please, then use cotton wool ball or very fine fine wet sandpaper and scrape off any debris where the orings sit on the cylinder heads.
Using the bolt you took out, go to halfords and get the stainless version inlet manifold bolt you just took out. The Hyosung bolts for inlet bolts rust very easily.
So go careful with them as they are known to round off!
For EGR = See the vacuum diagram linked above , which talks about how to delete the EGR
or see this page for info on what it does etc, there is no need to order it now,EGR Valve Blanking Plate / AiS Delete Block Off Kit – Various Hyosung Carb Models
It’s a custom job , Skidmarx UK makes them perfectly for the old shape models of Hyosung GT’s but they don’t / won’t make them for the new shape models , it sucks as i’d happily buy a lot of them.
Now , it is a custom job to do it on the new shape sadly, some DIY skills and possibly fibreglassing copying may be involved. Don’t quote me on this as i havent tried personally but possibly look in to the R1 seat delete or R6. it may possibly be easier than Suzuki ones i think. Your main worry is working out how to mount the old hyosung metal latches from your rear seat off on to the new seat delete unit, then to lock it on to the pilly seat on frame so it doesn’t fly off while riding 😉
Hello Gary , can you attach the picture of your old coils vs the new ones side to side? and the wires in your hands so we see what’s going on there.
All 125 carb = All of them until 2019 use “single socket spade connector” and “one-eye ring wire thru bolt” wire. That’s it.
So i’d be curious to know what’s happened.
I am happy that it finally is breathing back to life, this is great! – I will probably find out if i can start doing rebuild kits for these starter motors than buying a full unit , could just mean a small part inside probably jammed thats all.
– Neutral Sensor (is it on?) , has it shown signs of abuse near the sprocket ? – Clutch Lever Handlebar switch (no need to bypass but check circuit isn’t broken with a meter ?) – Stator Pickup Sensor ? = Check it isn’t gummed up with dirt or fishy (plug is Blue & Green , white shell) Check omhs under 200 , and report back? – Engine Black Box all fully connected ? I say black box as i am unsure it is EFi (ECU) or CDI Unit (Carby) – So will generalize them as the “black boxes”. – Is the sidestand switch bypassed (recommended) Also, do this safely! – Have a friend push you down a private road and drop to 1nd gear and see if the bike starts from the crank ? We’re doing a process of elemination now. The fact the button says “click click” , means the circuit from the start button going to the solenoid isn’t broken (ie. wires okay) I do hope in the end of all this its just solenoid or the 1st three electric parts above cutting sparks off. Update us all and i will keep an eye on this topic.
thank you for you informational reply good sir. I shall check all the above as far as i know it has a delphi ecu. Cheers
Also just to add, since its a Delphi ECU , you should hear the fuel pump prime when you turn the key on and the Fi light should disappear once bike has started too.
Fortunately, if you do this safely , have a paper clip of metal. Then download the service manual on this forum for the EFi 650 , go to where it says “getting error code from ECU” , if a sensor near throttle body is fishy or fuel pump or even the lambda sensor or ET/AiT (temp sensors) the ecu would flag a code “C45” as am example on the dash once you do the instructions on the service manual
The paper clip will do the same job as a rocker switch mentioned in the manual.
The GT650 shock is a direct fit, also HAGON UK makes shocks for the 650, so it fits the 250 fine.
Also look for older Bandit Bikes , they fit the hyosung swing arm, pre-2005 era im sure. Personally i am still on the same shocks as they came with the factory both GT and GV i own, i just adjusted them to hardest setting that’s all. been good for few years now.
