♠️ M77
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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 2012 (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.
They are incorrect. YTX-14BS is the correct size , only 9BS is used in the GV Aquila 125 due to their smaller battery.
“Some” GT125R bikes in the past came in 7BS (scooter) in the UK as that’s the cheapest battery a dealer can fit to save his money and push the bike out the door!
Get YUASA in my opinion. Powerline and chinese makers are rubbish, not good for your charge system or avoid lithium at all costs (Hyosung doesnt support lithium)
If no YUASA , get VARTA (German) , i used it in the past with no complains and sometimes UniBatt but that’s only if i can’t get the prior 2.
Good luck!
Hmm, have a spare bottle ready and remove the housing itself , so you can inspect it closely ?
Normally there is a sealing washer. If the hole size is 9mm , then go to any car shop locally (very common in cars) and ask for a 9mm hole DOWTY SEAL
Its a special metal washer that has a rubber-plastic insert in the middle.
Failing that, ask for “MANNOL THREAD SEAL” and wrap the bolt with that seal tape , a thin layer 2x then screw in.
One of these suggestions should work but if its the first time the bolt came out, the threads should not be damaged from removing it.
They never ran well with 17.5 pilots , so you will want to downsize back to 15 each pilot. Use 2.5 turns out as a base then see how it responds.
You may want a baffle in the exhaust as i have not experienced a 125cc in the past that run better without baffles.And is it still having its original airbox on ? without it you will have hell , a lot of us tried to do away with the stock airbox but the engine & carbs wasn’t having it even the 650 sister.
The middle screw of the carb isn’t usually touched once set by the factory, you want both butterflies to open at the same time but with a little bit more air to the rear (since it uses a bigger jet)
You did not say what the main jets are so i could not comment further
You are welcome 🙂 , i will mark this as [solved] , enjoy the rides!
`thsnks for your information , sorry not efi model . it’s a 2005 year.
No problem, a 1 man bleed kit should do it following what i said about the front potion where i sometimes do it the old fashioned strange way!
Ignore everything you hear about Hyosungs before 2020 online.
Unless they themselves have a GV300S , their opinion won’t matter, Hyosung has come a very long way from its 2001 early GV days. Because now it is an Euro 5+ bike, they have to take electronics even more seriously now.
Problems with GV300? = Not much , just take care of it, and it will keep going and it is Hyosung’s first 300cc liquid cooled motor ever. They did a good job.
The ONLY thing i would caution for reliability is NOT to use Lithium batteries (charging system designed for AGM battery) and upgrade to SHINGDEN Japan mosfet regulator. That’s the best electric upgrade for it. The OEM regulator is made in china , not in Korea anymore, so quality is hit & miss. I would put a japanese regulator there.
Ignition = Upgrade to NGK Japan caps because the stock caps can sometimes fail (it is made in china the OEM ones, it has plagued many motorcycles)
Coils = Uses Delphi Electronics, it is OK. 125 models were using carbs before 2018 and 300cc did not exist until 2019 , the EFi 125 sister joined in 2019
If you buy new, you still have a 5 year warranty , it is the first time Hyosung offered a 5 year warranty on a 125/300cc class machine in a long time.
300 would be a good balance to learn on it and keep it for a long time before you feel like upgrading to its GV650 sister. It is popular in europe now, there is also different GV300 versions , so choose the style that suits you (GV300R , GV300S, GV300X or GV250DRA-2025)
As you are learning on it, i would not worry about power, it will be there when you need it as you get more experienced. Chain Kits will be a future upgrade to change gearing (going faster etc)
I tend to fix a customer Hyosungs myself , it is always the older models before 2020 that need the most love and care but don’t worry too much on the GV300S , i can’t find much horrors of it yet (only stupid people blow up engines & blame the bike)
Tip = Use Motul 7100 oil every 1500 miles and use Motul Factory Line coolant and it will love you. (yes the Koreans do say in every manual that a commuter bike needs more oil changes than a seasonal rider, it helps it last longer)
Only downside i can think of is that it likes to eat brakes! – Expect to change pads often if its a commuter and it uses ABS so brakes will be engaged more , and it likes to eat clutch but fortunately we can throw away the stock chinese plates and use a beefier clutch kit (heavy duty plates) then its good to go.
Engine clearances = On the forum a member has done a guide about it already or your dealer will do it as part of warranty.
Tyres = They are OK in summer, winter can be sketchy but will be OK if you avoid ICE!, when budget allows get yourself Michelin or Bridgestone Tyres , I personally trust these two brands on my cold UK winters!
Just my random evening thoughts , hope that helps and go test ride it! – You might like it. 👍 – Hyosung has been around for a long time they made engine parts for Suzuki for years.
Excuse my grammar or spellings , i was typing fast before losing my train of thoughts!
You did not say if it is carb model or EFi, so my reply below will assume it is EFi model.
As it is CBS brakes, the rear cylinder being pumped also should help? Have you tried pumping the rear? – This is to make sure no air from the front has gone to the back or air at the back has gone to the front (vise versa)
A quick test = Disconnect rear cylinder or find a way to make sure the front caliper only has 1 hose attached to it going straight to the front cylinder , bleed & pump the brakes with a 1-man bleed kit found all over amazon / ebay. Keep doing it with the pads inside , so that all pistons push the pads together (don’t attach to brake disc)
Then disconnect it (dont push pistons) , connect the front and rear brakes together again (making sure the rear caliper has pistons pushed out to touch the pads without touching the disc.
Now Reservoir caps off from both cylinders for air to escape.
Push the pistons down flat inside the caliper (front) , you should see air bubbles in the cylinders making a sound or moving. Pump the front again until pistons full extend to touch the pads maximum, push the pistons back to flat, repeat this until you know the front is now good.
The rear should be getting better, push the rear pistons flat , and repeat, then test your brakes. It will be time consuming, but this is another “old school” method i use sometimes when i am doing multiple brakes at the same time or even my older generation GV that has two discs at the front!
Another way the bike loses pressure;
- Copper Washers on the banjo bolts need replacing.
- Pistons seals are hissing air or not sitting properly.
- Seals damaged for pistons.
- master cylinder is wanning. (if your pistons seized, your master cylinders where probably tired from fighting to push the pistons out?)
If it is a carb model = Don’t worry about rear (it uses drum brake) , just focus on the instructions i said about the front only.
Hey,
if you disconnect the RR itself, and do this:
– Rev the bike to 5,000 rpm maximum.
( I know the GV650 doesn’t have a Rev counter , so i assume you have a tach reader of some sort?)
(If not, try idle voltage + 1/4 throttle + 2/4 throttle) And Max throttle again (although hyosung does have a hard limit on their manuals for the AC output at 5K RPM mark, if it exceeds that , then further revs don’t matter as its replacement time)– Connect the meter to 500V AC and probe any of the 2 pins of the 3phase yellow wires in any order and do it 3 times.
Eg. Pin 1 /Pin 2 = Voltage?
Pin 2 / Pin 3 = Voltage?
Pin 1 / Pin = Voltage?Then let it cool down for least 12 hours outside in a shade (away from any sun heat radiation) , or overnight is best.
Get the meter out again switch to 10 OHMS (Ten) and probe those 3 pins again. And report what each combination says 3x
Resistance is the pretext to fry electronics (slow cooking) therefore the harness weakens. Hyosung has used thinner gauge wires on the EFi models compared to carb models. And also any oxidization of the pins , increases the resistance of the plugs connecting the stator to RR to harness.
Furthermore, is the stator OEM or aftermarket ? and I assume it is still using DAEWOO ECU? (We got Delphi in 2012 here in UK but also Daewoo units phased out by 2014) – It is the Daewoo Electronics that have plagued the 650 models and 250cc models but fortunately we can fix certain aspects of it.
Normally I put an extra red wire from the RR to the battery with a 10A fuse. I’d rather a 10A fuse blows up so i know it won’t cook the battery next and the RR is also still connected to the main harness which either uses a 20A relay box or 15A fuse or 20-30A fuses (Hyosung made variations of EFi harness over the years, so small things change)
Before I digress further, I will await the report of the stator information, it is best we start there. The RR can’t do anything until the stator feeds it.
i will assume you’re not using a Lithium battery (if so, I would advise against it due to the variable voltage nature of the Hyosung charging system which Hyosung manuals state it can tolerate up to 15V but 13.5V minimum DC to start charging the bike)
Keep in mind, if the fuel pump is OEM and suspicious or some aftermarket version, it may contribute to the additional charging system taxation which the RR will just get hot. Daewoo pumps are specific as they run different pressure ratings compared to later Delphi units. Daewoo pumps are Black with OEM numbers printed on it (the Aliexpress clones are black/blue intended to run the Delphi systems – Daewoo stopped making their pumps as they went out of business. So fi you find another used Daewoo pump , look after it.
I can’t remember if it is 3.5BAR or 3.0 bar but it is possible to manually check the pressure yourself.
Something else came to my mind but worth thinking about, in the context of the charging system, this “extra” resistance (aforementioned above^) does not necessarily mean the regulator will “cook” due to higher current; rather, it indicates a failure in the efficiency and thermal integrity of the stator itself. henceforward we must address the stator first. The general consensus amongst 70% of Hyo 650 owners who keep their bikes longer than 5 years (not the stupid 1 summer riders who switch bikes after abusing it with cheap china RR’s and fitting lithium batteries or crashing them because they are too throttle happy on the streets as their race track are ones you should not seek advice from) is to make sure the Stator is in good spec all the way through , connectors are not oxidized (common for brown burns to to happen there) and fit MOSFET RR’s but beware there is a LOT of fake mosfet RRs and even the fakes are now becoming almost hard to detect , real Shingdens (mosfet kings) are very expensive brand new. A used one from a local bike you can see running with your own eyes is better salvage but still costly. OEM RR’s have always let me down as Hyosung doesn’t make them , so its an outsourced product.
Also where i mentioned checking OHMS of the stator cold (about same temps you would check valve clearances) , this springs to mind , If one phase is example 3OHMS and others are different like 2OHMS (Pin 1+2 = 3Ohms , Pin2+3=2Ohms , Pin1+3=2Ohms), the RR must handle an unbalanced load. the OEM RR uses either SHUNT or older diode tech (depends what Hyosung gets as they have many variations of their RR’s being made, it’s hard to keep up) , which dumps excess current “somewhere” to regulate voltage. That kind of imbalance could cause uneven heating of the SCR, or diodes within the regulator, leading to premature failure as you said that as soon as you run the bike , it is not long before it’s “cooked?” . Just my random suspicions but please investigate and correct me if i am wrong as i am hoping we don’t have bigger issues on the bike and it could just be something small that was overlooked!
Can you show us a picture of this part ? Upload it here. Just to make sure Hyosung hasn’t updated the spring design (caliper stays the same) but spring (anti rattle might change as they outsource these things to other companies making it)
