♠️ M77
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Welcome! Hope to see the completed upgrades you will post on the forum 🙂
Not many people do ECU flashes as they are afraid that a false move could mean they can’t get a replacement ECU , however , they try to improve the sparking a little bit , the most improved mods would be something like a 520 chain set and a good clutch upgrade for long summer trips.
If you have OEM caps, replace them with NGK ones , that’s the only major electrical complaint people have in the UK , sometimes the stock caps ruin the coils next. And invest in a good regulator! That’s pretty much it.
You could at your own pace upgrade the tyres too, so its less suicidal when riding in the rain, i was never a fan of the stock Tyres Hyosung used in the past. #
I believe once you go 520, you won’t go back to the tiny chain 🙂
Vacuum should not be blanked , the tap will need it and the fuel pump is actually needed too. The 125cc uses a DF52 Mikuni Pump that was made for the Hyosung family , so the GV650 actually uses the same pump, it has a flow rate of about 80ltrs per hour, no way the 125cc will maximize the fuel pump , infact it is needed to help it sustain speeds at the top gear as it works on vacuum pulses from the inlets.
Check your inlet O-RINGS , usually we check the O-Rings under the inlets before replacing anything else.
China inlets = Chinesium , it won’t beat the OEM quality but it will get you on the road asap until we find the super rare originals!
Check your oil filler cap, sniff inside hard, if you smell fuel , it sounds like fuel tap is “wide open” after engine is switched off , would suggest future problems with piston rings or hydrolocking too – The tap may have a burst diaphragm
Just some of my thoughts , hope any of what i said made sense to you ?
Regards
This is fantastic news! – Who could have thought ? but you could see why 99% of Hyosung owners go strictly NGK caps immediately as the factory caps were made by a company called “Golden” in china, they always caused random issues there and there, so it wasn’t worth the anxiety. Nice move on the coils too, Tourmax is OK, japanese parts, it should mate well with the RR.
For now, leave her at 25amps as as safe buffer. Service the bike , and take it for a short spin not too far from home and come back.   While the bike is still hot, measure any resistance of the new parts and other sensors, to see if they are within the safe margins ?  If yes, then we should assume to go for another longer ride and see how it actually feels (power , throttle , idling at traffic, fan temps (if the fan spins etc) ) now you get some real world data for yourself to make a better judgement.
If you feel anxious, carry a spare jump pack to start the bike and limp slowly back home but heaven forbid , as you said it’s idled for 30mins without a hitch.
Another thing, find out if the amperage changes when the 55w headlight is ON or OFF , and watch for any RR wires getting hot.
I have no correct answer yet in regards to the Fi light , despite the bulb working when manually triggered , i must assume it being OFF is a good thing , find out during your longer rides if it ever blinks whatsoever ?
If you come back and say there is zero issues during the test runs , then you must be ready to go! (Hopefully)
A GV250 can start with a 9BS (factory size) as it is smaller than GT250 battery tray , you can start with 9AH,  the GT250R has the luxury to use a much bigger factory size of 14BS since there is more inside the battery, you have a better chance of starting on a 14BS than 9BS , just simply it has more capacity & CCA.  a CBR Honda can run on a 9BS battery , 9BS is common on many bigger japanese bikes of varying styles and different electronics.
IF you can’t find 14BS , try 12BS which is a nice middle ground anyway.
I can’t answer the starting questions to be 100% true as I don’t have the bike with me to do a deeper analysis , so i can only suggest likely cuplrits  and reply to the error codes given by your ECU. However, if the ECU is saying the Lambda sensors need looking, it is a good idea before they fail mid ride.
If you go that far, you can see if the starter motor is tired (prematurely worn out?) and check your engine flywheel SPRAG CLUTCH , it should not be slipping but it won’t hurt to check. This allows you to also see the SPRAG SPROCKET teeth too  (2 items to look at there)
Car = Turned Off yes, you can jump start the bike. but i would not depend on a car battery for a complete judgement, we might miss something else, we need to know the bike can run on its own battery first, it should not ever require more than double its original size.
NGK caps is what we all use , we dont have much faith in OEM caps , suzuki gets the same trouble with their caps sometimes, so NGK wins.
Also replace the coils if they haven’t already .  Fresh CR8E again as they foul easy.
Stator unit , probably be your last item  (it directly , i mean directly affects starting and general running etc.) – If its haywire at any point, the ECU will shut off or get grumpy to start.  Probably flag an error code “no signal for pick up coil” etc eventually but if the stator is good, leave it alone for now.
The stator has 2 plugs . 1 is for charging (3 yellow wires) , does not affect starting unless fried (thus frying the battery and regulator etc if its shorting out)
other one is a 2pin plug = this is what the ECU wants from the moment you press start and general running all day. It can’t live without it.Ignition Coils = ECU won’t know if the coil is failing , so it wont warn you , go and measure the coils for their primary and resistance OHMS as mentioned in service manual and report back.
O2 sensors are needed for ECU timing & fueling.
Your battery should be 12.8V when the key is out of the bike (turned off) , then a drop of 11v while crank may be tolerated but dropping below 9v will 100% trip the ECU to say “battery voltage too low”
Get another starter motor cable = Yes a starter motor cable for Hyosung specifically, connect it to the battery NEGATIVE and then connect the other part to the frame (unpainted part)  = This starter cable is thicker, and can be used as extra ground for the bike.  Do not connect it to starter motor! or anything postive.  I really hope i made sense!
I assume those codes are flashing sequences of the red Fi light,  = They all point to the oxygen sensors (exhaust lambda sensors ) (high Voltage & low voltage errors) , so they may be going haywire tripping up the ECU. You will need to replace them and make sure the ECU plugs and ECU pins are very clean too (no liquids , just compressed air only)
Get YUASA YTX 14BS or VARTA 14BS (german brand) = That’s all I use and ever recommend for EFi machines ,  i can’t comment on other cheap brands as i don’t like them and they have always let me down eventually.  Though any battery will crank a carb motor as it has far less electronics to power up , go figure!
Is it a 2003 silver frame where it uses a “frame mounted” tap and the fuel tank itself has 2 holes coming out of it to feed the tap thats on the frame ?
or a newer black 2005+ frame where the tank itself has its own tap (no need for frame)
Feel free to upload an image of your setup now if you want to clarify ?
Great to hear! – Topic now marked as resolved, incase anyone comes across this.
Did you get a can of carb cleaner and spray the airbox outlets that swallow the carb and also spray the intake pipes attached to engine cylinder heads for any revs changing ?
Possibly a loss of vacuum under the engine intake pipes where the O-rings are (there is o-rings that sometimes need changing) , tedious process as its awkward to remove the airbox but fortunately forum has 2x tutorials to make this a whole lot easier.  Check the Air Lines thats feeding the pump for cracks ?
Large fuel lines would just hold more volume inside which is what you want , then more fuel is readily available as soon as the floats open inside the carb.
Did at any point the carb got opened to change jets ? Micro dust particles have entered the carb before closing up? or is there a chance the floats got bent even if it’s just 1mm off  (see this link below to check float height as it directly affects how much fuel the carbs have before it shuts off , too much adjustment will simply leak out of the overflow or drown the engine – be cautious.   or look at possibly jammed floats not opening fully?)
Otherwise , clutch switch and sidestand switch (even if bypassed would have corroded wires inside the harness, strip back and see.) – I would NOT bypass a clutch switch though especially on EFi models.
Just quoting this , as those will cut sparks off too. You did not say “Cuts out when going in to 1st gear ?” ??   I could not understand your previous phrase “Bike shuts off when put into her intermittently”
So i will assume its electrical and needs stripping down to investigate either way and contact cleaner will definitely help if some pins or wires have oxidized bad causing a signal loss
You mean it cuts out as soon as its in gear ?
If its EFi , have you downloaded the service manual on this forum to get a flashing sequence eg.  the red Fi light will blink with pauses
10 blinks, 3 blinks , 3 blinks , 7 blinks = It repeats ,  this is Stator Sensor Coil for example.   The ECU should let you know why it didn’t want to carry on , it should report itself on the dashboard once you turn the key on,  dont start it.  Flick the kill switch 2-3 times quickly and wait for the ECU to flash red codes on the dash.
Report back , if you struggle to understand the sequences , record it on your phone and upload the video to GoogleDrive/DropBox etc , and get a public share link,  post it here and we shall see.
Otherwise , clutch switch and sidestand switch (even if bypassed would have corroded wires inside the harness, strip back and see.) – I would NOT bypass a clutch switch though especially on EFi models.
Hyosung sold Gv250 models with carbs until 2011 in some parts of the world, Hyosung introduced EFi models in 2008 with a SENTEC ECU (ultra rare now) and sold them until 2009 , then 2009 was the start of 2nd generation EFi which had Daewoo ECU until 2012  (then it is now Delphi ECU present day)
So being a 2009 of yours , I don’t know what’s under your hood (carbs? EFi? – Though EFi manual is at the forum to get error codes , if its carb model then it has way less electronics to diagnose)
Try to ring Startright Motorcycles in Yorkshire , they are the oldest hyo dealer and we sometimes buy stuff from them for the shop.
It is hard to get one these days but i am sure they could still have one, so worth a shot!
If its the Spark Plug Leads rubber sleeves , you may need to check the coils are not “arc-ing” (sparks leaking out of them or out of the plug) which i would be careful touching the cylinder heads as you will get shocked! (I found out the hard way many many times fixing customer bikes)
If the “inlet manifolds” which hold the injector bodies to the engine have split, i can’t tell, you will have to remove them and inspect their o-rings to show us if possible.
It looks like the electrical side and intake side where you’re looking at is now the issues  , i don’t think the ISCV is the issue yet.  (It wont work or fails early if its over-working to try maintain a stable idle where the bike is leaking air in other places or dropping sparks for a split second thats your caps and coils (hence every GV owner we know replaces the coils and caps as the 1st priority, then worry about making sure there is no air leaks before closing the bike back up)
Strip her down and investigate deeper on those intake pipes.
Regards
The idle should 1,000-1,200 ice cold if the engine compression is good, Carb is good , and valve clearances are not tight, electrics are OK (click here) , then of course let the bike idle for 10mins, it will nicely climb up to 1500rpm
Hyosung says it should be 1500 rpm when hot  (I would recommend 1600-1700 rpm hot as that is best IMO , however don’t exceed 1800 rpm. If you idle over 2100 rpm all day for example, you will find that the engine heats up too fast and may slowly burn a hole in the piston)
Sometimes idling issues could just mean air leaks , so you will spray carb cleaner on the intake pipes and see if revs change or maybe you need fresh intake o-rings (like these ones) , most people don’t think O-rings are important on the intake side but on the 125cc it matters a big deal.
Hope that helps!
Good discoveries there!
As far as i know on my side , all the GVs i ever touched being Fi models , they used a 30A fuse for the fuel pump side, its own fuse box i should say, the 2nd fuse box will be 15A for general electronics , the lights took 20A relays , and there is also a mixture of 20A and 30A relays in the battery rack.
I don’t know if you have a minor harness revision for your market, can you confirm how many relays the bike is using and how many fuse boxes are there , they should match the UK daewoo ones I lay hands on.
The black pump is very thirsty , it draws a lot but it is a given since it’s constantly running.
Heat is the enemy => Check if possible the values of the water temperature sensors in the thermostat and radiator fan switch , and other temperature sensor on the bike.  Now i did get an error from the ECU where it ran cold fine, but it was rough , the Fi flashed a sequence telling me to replace the engine sensor that checks cylinder temp.
Another heat problem i faced with a different GV was that it actually shut down mid-ride and had to wait for it to cool down, it was the stator’s pickup coil gone haywire and the engine was popping a lot.
If you unplugged everything except the pump to keep the bike running , I would check:
- Temperature related sensors / Lambda Sensor
- Fan Switch (unless the radiator is ice cold for 15 minutes and the fan hasn’t come on yet?)
- These sensors tend to send OHM readings back to to the ECU, so if the value is off , the ECU just cuts off the fuel pump supply., then the bike dies.
You mentioned that sometimes you hear the cylinders dropping in and out?
- Would the primary and secondary resistances of the coils be affected too drastically ? Ie. (the coil without the CAP attached would say 15K Ohms but after 15mins, it jumps to 40K ohms hot ?)  OHMS will go up and down based on temperature which is normal but not too much as there is a range of values accepted by the service manual.
- Get NGK Caps if possible (if you have already , check their resistance without the coil attached) , we don’t know if they waned, then the sparks drop when it gets hot , as it gets pretty hot inside those engine heads where the plug caps go to. So hence we really don’t trust the OEM caps (the black ones) they are the first things to go.
If not, try SV1000 caps (should be OEM ones) and yes it is a good call to check your plugs and the coils themselves.
I could not give you a true figure of what amperage every item uses on the GV650 , as Hyosung changed many parts over the years (Carb, Mitsubishi EFi (rare), Daewoo, Delphi , along with harness revisions sometimes for the same ECU. My delphi uses 20A relays where the Daewoo used a mixture of 30A and 20A, but i would change all the relays and see if the power draw has improved ?
I would really hope the ECU is OK, but be ready to hunt hard for a spare one (practically scour the earth for it) or get a Delphi Harness and Delphi ECU as plan B if we cant replace the ECU , however a crashed GV650 will be a good donor for testing also before messing too much with your live one, so keep an eye or just as a back up.
ECU could possibly die due to heat (I can’t confirm if it has an internal temp sensor like a PC CPU does where if it reaches a TJMAX it shuts down to avoid as fire but , i believe this daewoo ECU is a little more primitive than the Delphi ECU, so i can’t assume 100% correct on my assumptions here , or otherwise , we could suspect a small piece of circuitry inside the ECU is now more heat sensitive since it was spiked before but i hope not,  otherwise a dead daewoo ECU just wont even entertain the pump to prime before starting.
For your RR, if it gives off 14V but blows a 15A fuse, that’s crazy , we might have a problem of resistance , i only ever experienced a blown fuse from the excessive draw from the fuel pump waning or the stator was waning (hence on my previous reply in regards to heat on the connectors)
I have a theory , what if we source a battery pack 12V a good one that’s not going to harm the motorcycle , disconnect the stator, disconnect the RR , let the bike run purely of the battery pack but do add an inline fuse to be safe and see if it dies out ? –  You could measure how much juice it is drawing from the battery and how rapidly does it deplete the battery , you could use another spare good bike battery for this too.  It is a theory for you!
Hey,
Sorry if this reply was too short but this came to my mind, as i was dealing with this a few days ago!
We got a GV EFi that stopped charging and we found the connectors melted , despite being a new stator! – However, it turns out the stator didn’t match the flywheel for whatever reason.
So to test it, we got a 337 code (no signal from pick up coil) , fine… We swapped it again with another stator ,  the bike ran,  and the connector was replaced.
This was a 3 phase plug, so while the bike was running for 5 mins, the various Mosfet RRs we have on the shelf were all saying 14V , we put an inline fuse on the battery RR wires to be safe.
I kid you not, the Stator’s 3 phase wire was getting hottter and hotter to the point where , I wonder to myself , perharps the stator simply is internally shorting itself or it’s on the wrong flywheel (hence on certain models Hyosung sells stators with flywheels together)  or the wires were too thin , mind you the connector is new and has nice brass colour pins , it was getting too hot.
I have not solved this yet as the bike was being stripped down in to a carb conversion instead (less electronics to worry about later for the new owner!)
This was a Delphi 2012Â (the very early one) , so it still had some old daewoo electronics and ran fine on its black fuel pump.
Check your bike for:
- Wires getting warm ?
- Headlight wires getting too warm ?
- Smell the plugs for any signs of burns?
- Check the Fuel Pump Relay & Other Relays = If they start going funny, they will start taxing the stator back.
Just some ideas to try if i had not already mentioned
Your ODOMETER will probably stay that way as sadly i went through it myself, the old OEM RR briefly overspiked the whole harness, so it made things go a little haywire , except my ODO went to O miles , had to start over again (where it said 10,000 miles before) , likely ruined a battery or a capacitor inside the ODO board but i did not check at the time as the rest of the clocks where fine for the rest of the bike’s life.
Though 25-35V AC at 5K rpm isn’t good , it should be least 60V on each phase as per OEM ?
Though not possible to acquire anymore but the special tool used to read the ECU is Hyosung specific and they only ever gave it to dealers for warranty claims , so i was not fortunate to get one  (I came on the Hyosung scene in 2015 circa , so Hyosung had already moved on to Delphi Electronics!) , hence you were not able to properly read the K-Lines of the dealer plug.  We simply rely on the flashing sequences of the Fi light.
Daewoo as i know it , will flash red , while alternating 0 , Fi , 0 , Fi on the dash = Fuel system woes or ECU gone haywire.
If you don’t get error codes while it is running, that should be a good thing I hope
Delphi as i am on now, will stay red until i press start, once the bike fully starts, the red light goes away.  It will flash briefly during a ride if there is issues with it.
If you read the service manual , make sure its an 09-11 as  from 2013 onwards is Delphi , so error codes in newer models will be confusing where it doesnt apply to an older ECU.
If it is a carb model (earlier than 2008) , then the issue likely will be either:
Wanning Stator (the pulse sensor may go haywire and the bike can’t run without it)
HT Caps = too common , so we tend to upgrade to NGK ones and forget.
Coils = There is a service manual on the forum that your mech can download to confirm the resistances in primary and secondary are within OEM range , unless the coil has internal failures  (likely caused by the failing HT cap or sparks arc’ing out of it) , try to make sure he puts a good coil there.
Plugs shot ? = Try fresh CR8E plugs to confirm, if the bike uses anything other than CR8E or CR8E LASER , it will make sure you get stranded, they dont like “IX Blue box” plugs (Iridium IX ones , not to be confused with the trusted Laser Iridiums)
Check the Regulator is in spec (#2 issue that is common, so unstable charging may make things haywire , if you see a chinese regulator, toss in bin and get Japan SHINGDEN MOSFET ones like the ones you see on this site , if your mechanic can do it himself , he needs to be aware of fakes out there)
If there is 3 things on the electrical side every 650 owner should do , would be NGK caps , Shingden RR & Good plugs.
Real OEM coils for the 650 (original) are made by Mitsubishi Japan and share with other suzuki bikes of the 90s , but Hyosung has since changed them to either Hankuk Korea (they are OK-ish) or Delphi (later EFi models)
Hopefully above ^ should fix it as we don’t want to replace the CDI or other black boxes on the bike as those are not made anymore, so do all you can to preserve it!
Good luck
seems to be OK, doesn’t look burnt or even bent , so i would also next time check the intake system any splits in the air lines , and the intake manifold o-rings themselves if issue continues, a dead iscv wont even allow the bike to start and idle. I had to replace an ISCV from someone’s older 2015 GV which is totally different from yours but the bike screams for 1 second, then dies right away. As soon as a new one was fitted, it idled OK.  I found out the ISCV unit was soaked in water, bike was left to rot outside without a cover, that poor thing but i digress!
upload a picture here to see what has happened to the plunger ?
It should normally be straight so it goes in and out easily , otherwise if it was jamming inside, it would have worn the circuitry inside the unit, it should only move when the ECU operates it.
Check your inlet manifold o-rings, air can leak through there if the small O Rings have given up.
Upload it now, it just wouldn’t let you post it as your 1st post (there is a forum bug that’s annoying to fix right n0w
So go ahead and post an image here and we shall see!
If not , just upload to Google Drive/OneDrive etc make a public folder there call Hyosung Forum, then share the public image link here.
