♠️ M77
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Hi Guys, I have tested the stator and it works well. Also ignition coils and sparkplugcaps are ok, as tested with a multimeter. The Regulator and the CDI seem to be faulty. The reg is already on shipping, thanks again Marcel. Can I replace my CDI with any DC CDI from Amazon? Or can/would anyone recommend an explicit one for replacement??
Sorry for delay.
It should be only a “GV125” cdi specifically for yours. Because some Hyosung GV CDI’s have 3 plugs and some have 2 plugs.So i will assume your GV has 2 plugs under it. Replace CDI with the same one with 2 plugs for HYOSUNG GV125 only.
Other cdis from any bike or random ones may not work or will damage parts sometimes.
However, do test your CDI with ohms meter if you can , if you can try manualslib website for GV125 Service Manual page for your bike, it will show you how t test cdi.
(((I will upload more manuals on this hyoriders site when i get more time)))
Because the only way the bike gets power to the dash is via:
- Fuse/Relay box = as per simon
- Ignition Barrel (even its wires) =
HOWEVER, if the mechanism inside the “key barrel” acts intermittent, it will translate to power cuts instantly - The entire loom itself may need investigating because if there is a “shortt” anywhere inside the cables fraying or touching exposed inside the tape jacket
OR
The 1 cable somewhere is touching the frame, that will instantly turn the bike off and possibly blow the fuse too
However, if the “rear” and “front” lights stay on , and the dash stays “off”, then investigate the dash area and its mini loom that tries to join the main skeleton harness. Just a little heads up.
Hey welcome!
I hope you share pics of the bike when you get it on the forum, and wish you the best life with it 🙂I’d usually stay away from places like aliexpress for hyosung things as the general consensus on the whole internet can attest that fitting china stuff on hyosungs usually means buying twice or problems later of some sort. so i’m not sure to advise further here sadly.
However, because GV125-EFI is an entirely different animal, it shares zero parts from its older generations , so much so that even all the part numbers i know in trade all have “1234567KGZ0000” as opposed to older hyosungs having “12345HG0000”, cross referencing will not be easy until you yourself see the gear switch in the flesh aswell as seeing how the shift linkage works.
Hell, ive seen a chinese item with 2 magnets that basically signal each other on every gear shift until the rider stops , and the gear indicator is ofcourse its own LCD.
When I press the starter button the engine starts to turn over and then stops with a clank noise. I changed the starter and battery. Still happens but it’s intermittent.
Are you certain there is no missing teeth on the big sprocket that is behind the flywheel drum ?
It will start to turn over and then come to a crashing stop in the first second or so of kranking it. It almost sounds like it’s hitting something as it’s trying to turn over. The only other observation is that when it’s having this problem the wires to and from the solenoid get very hot. I also checked the starter clutch and it is solid in one direction and spins freely in the other direction. Any ideas would be welcome. Thank you!
I am very suspicious of the “Sprag Clutch” that sits behind the flywheel drum, if in doubt, i’d replace it. Sounds similar to a bike i’ve worked on a while , it was a GV250 that was notorius for having missing teeth of the sprocket or sprag clutch got too old / annoyed causing the starting system (electrics) to get drained fast
– Alas starter motor dies sooner from stress cranking
– Solenoid, burns out.If it starts on pushing and dropping to 2nd gear.
This issue now points to funny behavior that concerns these parts mainly
- Starter Motor Unit
- Check the wires, if in doubt, use thicker gauge wires.
- Sprag Clutch
- Flywheel sprocket
- Hopefully flywheel “Half-MOON” shape key is in still inside the crank shaft where the drum slides in to, so it clocks the “drum” only from free spinning
(I would assume so, otherwise if a drum free spins, it will certainly undo the center flywheel nut)
Red Paint is “Hyuindai Electric Red”
You’re welcome 😉
50 will will have a slightly higher heat tolerance before the oil starts to break down. The “10w” in the bottle must stay that way forever as the hardest life the engine gets is also when you start it , the oil must race to the crank and lubricate so the parts don’t degrade too fast (metal to metal grinding)
15w/20w is too thick for our climate. However, 40/50 on the bottle (without “W”) is safe for all year use.
Hi Marcel, the revs rpm reading, I heard it could be an empty battery.
RPM Revs reading comes from dashboard wire that is colour “Yellow/Black” (usually) and it works by signal from these devices below (so check them)
– Stator
– CDI
– Harness (Mystery sensors inside hardness/ aka. Mystery diodes)
– Ignition CoilsHave a look at this topic below for some ideas on electrical troubleshooting and how to test parts with a meter
It is a GT250 yes but still carby, and they sometimes use same coils , caps, & regulator as GV125
Only stator / harness / switches and some other electrical parts are only for GV125 but either way it should give you some idea.
No it will love highway rides more than little city rides because there is not enough speed & air in the city to keep it cool due to speed limits. But the city sucks because too much time is spend in traffic and idling.
Motorways are fine.
For even better benefit , get a Hyosung 250 Cooler (GT250 or GV250) and the rear cylinder will thank you. The GTR gets a little less air at the rear engine to cool it because it has plastics hiding it (for aerodynamics and sporty look). The Naked GT do not have the problem.
Also Ester oil helps, use good quality oil. In my own opionion (because everyone on the internet always has a “favourite” brand) but i can assure you Hyosungs love Motul or Silkolene oil (Motul 7100 or 300v //// Silkolene Comp 4 or Pro 4)
I use 10w40 in winter and i use 10w50 all summer. I do not buy 5w because its too thin, and avoid 15w/20w because it is too thick. Our European countries do not need 15w/20w even the UK (even if its out of EU, it is still mostly a cold climate)
Hi all Still having starter issues. Is there a way to adjust the timing on the GV65O 2007 and would that help the starting problem? Thanks
Can you explain more of the starting issues?
Also secondly, do you see good sparks from the plugs and fuel is getting to the cylinders?
Motul 7100
Motul 300v
Silkolene Pro 4
Silkolene Comp 4These 4 are always what i love to use and wouldn’t even touch the likes of castrol or some other hyped up brand. Silkolene & Motul Ester oils do exactly as they say and i always seem to get a better mileage out of and gearbox is always smoother to shift thru , like butter.
But other brands work , however after 500 miles or something they quickly turn black and the gearbox can feel crunchy sometimes.
Just my 2 pence 🙂
Hello Marcel, since yesterday the speedo does not work anymore. which part of the motorcycle is responsible for the speedo?
Do you mean MPH reading or revs (rpm ?) or fuel gauge reading ?
Hi Marcel, I have already done valve clearance —> everything in tolerance Clutch —> Already replaced
—> air filter new —> manifold orings new Regarding the cap, just any cap from a mechanic near by, not even new I think. There were cracks in the previous cap. How long is the shipping of the coils from the store? Caps would be good too in that case.. What do you think about the CDI?? Not possible that it causes the problem?An NGK cap would be better, some caps have too much resistance. (20 ooo ohms etc, not good for carby hyosung) , Hyosung oem caps are under 10K usually, NGKS would be less, like the ones i keep on the store.
Speaking of store, you will need to send me an email with your address so i can see how long it takes to arrive for the coils.
CDI can be faulty yes but usually when it is dead, it stops sparking. You may download the GV125 service manual and check resistance of the cdi terminals with a pocket meter.
12 Bar is very good, that is like 175 PSI for a 125cc Hyosung twin. So engine is OK.
For the engine, now if the top speed is poor, i would definitely check with service manual these 2 because it is also true;
- Valve Clearances
Get a feeler gauge and follow instructions and see if any valve is out of spec?
Tight valves = hard starting / overheating / poor speed.
Loose valves = noisy / poor speed / dangerous if too loose, it will annoy the chain tensioner. - Clutch Plates
Get Venier Calipers and measure clutch springs and measure plate thickness vs manual oem limits.
Bad clutch = bad speeds.
Beautiful big (heavy!) girls the Korean bikes are but they like to eat clutch and brakes!
So if engine is sorted, next step try these tips:
– Show us which caps did you get ? If they are NGK CAPS, then no problem, ignore this message.
– Next tip, replace ignition coils. (Better ones , like these we have )
Do not buy rubbish chinese knock offs.
If you do not want to wait for us to ship coils, then you can go to your local junk yard (scrap yard) and find SUZUKI SV650 1999 (1999 only!) good condition working coils and try them.
They are BIG, so they may cause issues fitting it!
Hyosung GT650 (2003 iirc) and SV650 use same coils because they are japanese and made by Mitsubishi. These are the “only” korean coils we don’t mind keeping haha. After 2003-2005 iirc , Hyosung used different coils
Fuel System next,
– check air filter is new and clean ? If i have already send you new air filter, then ignore this
– Carb cleaning by ultrasonic will help.
– Did you replace manifold ORINGS rubbers ? (intake pipe o-rings) ? Maybe i have already send you new ones ?Hello!
Welcome to the website, it is good to see you here 🙂 , we have other riders from Japan too , this guy below is a regular customer of mine and he rides a GV125 too, this is his profile.
https://hyoriders.club/members/eisukesaito/profile/If you see other riders in Japan, maybe you can share this website to them too 🙂
I like your bikes, the Side-Car (we call them in UK) , is quite a rare thing to see on our roads, that’s amazing! Nice work!
You are welcome to share more pictures here ;Hey,
I am very happy for you that the bike finally ran, i did think the CDI was sort of the last resort item for sparking woes, now if anyone has similar woes, i will make sure to make them digest this topic. Very informative! Hell, you even laid out you tested some electrical components and what the specs are.
Usually some folk can’t or won’t want to read the manuals if it is too confusing for them , but not always!
I’m quite jealous you won a cheap auction backup bike but that will come in handy as parts donor for your racing days, you won’t have to wait to replace anything or just have an extra girl ready to go! A little switcheroo won’t hurt haha.
As for the harness, if the ignition system has to pulse 10,000v to spark the plugs, i would not be surprised if the koreans added one way diodes or some other mystery sensors embedded in the harness so that things don’t retrograde back if something doesn’t go to plan.
The horn does draw some power to be fair and it’s always live (as long as engine is running) , so all the rider does is press the horn button to complete the circuit. You don’t have to be a full electrician right now to know sometimes bad coils will arc the sparks or zap signals out of their HT leads , the harness must not get fried back or the cdi. It isn’t fool proof since the stator unit can still blow the cdi or blow ignition system system.
Just make sure it produces 70v around 5k revs and never exceeds 90v in any revs , it is almost the hottest thing on the left side of the lower crank.
When starting the bike -> magneto tells cdi how fast the rotor is spinning -> the CDI then tells the dash board (rpm signal bouncing around 600 rpm) , now the cdi next has to communicate with the rest of the ignition system to spark the plugs (as long the clutch switch & kick stand doesn’t prevent the CDI from doing so – – ie. safety cut out — (ie to avoid setting off with the stand down or starting the bike without holding clutch)
Neutral sensor isn’t foolproof , it may say N but gearbox may still be “slightly engaged” , alas when bike starts , it rolls 3 seconds later and falls , oh yes , i’ve witnessed it haha. I always make sure to roll the bike forward and back anyways to make sure its really neutral , keep gear linkages greased up and sparing no expensive on quality oils. That will keep the valve train silky smooth (oh yeah, the engine doesn’t have a camshaft under the gearbox too)
I’m a bit sad you’re leaving haha, i though the bike would stay married to you even if as a winter hack ?
Keep the big toys in hibernation till next summer even.
Perharps a GV650 will tempt you ? haha
The 2 black spade connectors going towards the oil cooler is for the horn system.
I know even the 650 has a wiring diagram that says “igniter” on it and it is usually a strange mystery object or plainly exposed , however korea makes the harness.
Otherwise if there isn’t some sort of mystery sensor for the coil at the front section only , then i will suspect the harness itself allow the CDI to deal with igniting the coils directly without some sort of diode assist / or igniters.
Since fitting new coils …. These would also cut sparks off (and i will also assume they have been checked already ?)
– > Clutch Handlebar switch (bypass it, because it’s a race bike, you won’t need it unless your local club says it must be present)
– > Kick Stand switch (bypass it)
– > PickUp Sensor from the Stator (but it works as its circuit isnt dead and is in good ohms spec)
– > CDI unit.
-> Regulator Unit (You can contact some local wreckers and ask for a Kawasaki Mule regulator and a genuine Yamaha r1 regulator. Please avoid knockoffs because it’s not fun to see regs in smoke – its so common usually electrical issues we tend to only blame the coils, reg and stators because Hyosung doesn’t make them , but they are outsourced parts to some other korean company to do it. I digress, sorry.Here is another hint, if you have a Digital Dash connected to the harness, you will see the rpm counter bounce when its cranking – That confirms it magneto is spinning 600 rpm as the typical speed of the stator motor to crank a heavy 250 flywheel.
I know you said the harness is checked from end to end with a meter, every wire colour you can find matching, so that’s great. I “should” assume the harness is okay , i can’t see it being fried from the pics or toasted up.
Perharps a spare harness from the wreckers and swap over the diode sensors and try again also ?
Keep us posted please. This is interesting.
Yes, Hyuindai Electric Red 🙂
Credits to a member from facebook, so i’ve remembered it ever since. I know because my bike is red and i like colour to match exactly.Just gotta figure out the exact Korean car that has diamond sparkle white , if anyone ever knows , share it away!
It could be advised to replace the front ignition or both of them (and keep one as backup).
Also when bike is running this is OEM values for charging system on your battery
- Idle 1800 rpm hot = 14v
- 5,000 revs = 14.8V (15v max)
Regulator that’s producing 13.x or 12.x volts in any revs is not good. And to be honest , a lot of owners worldwide replace regulators for better ones because the Korea ones are not great. Hyosung does not make them but they ask another Korea company to make stators and regulators for them. But i digress sorry , have a good session testing it and let us know.
Also, maybe get a USPRO Compression Tester from Amazon and check your compression for your pistons , after the engine is about 20 mins hot.
Sorry for the delayed reply. You got this 🙂
As per photos , you are correct 🙂 Diodes / Mystery Sensors and the black ball thing is likely the “igniter” which is part of the sparking system too.
They have wrapped that so tight with only black wires out of it suggesting its not something that fails often , i hope not.
