♠️ M77
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This is commonly , i mean commonly across the hyosung 125 to 650 twins is the regulator that fails a lot and tends to take the stator with it or the stator has waned down fast and has took the reg with it. bike running like its on limited juice off the battery then battery has issues.
Start your bike , unhook the 3 yellow color plug coming from the stator , and rev to about 5k ish , it should say about 80v AC (AC) strong across all pins (ie. 3 pin means join any of the 2 pins on your meter but do it 3 times so that all 3 pins gave the same readings)
and/ or bike is totally off , the stator yellow plugs will be about 0.5 ohms ice cold (less than 1)
the regulator should be saying 14v at 2k revs , any 13.x v DC (DC) readings at battery will mean regulator needs attetion.
There is different types of regulators used on the hyosungs , they are not properly made so even i wouldnt dare sell one for a 125cc bike , the 650 wont play games. Common upgrades are the shingden ones with some fabrication , but a “plug n play” reg would me i need to know specs of your reg or its part number printed, i can always build a mini harness to retrofit the regs that are sold on this site , I pray the stator is in good healthy , they don’t make em no more in KR , so aftermarket is usually the way but never ever ever chinese.
Happy holidays , im sure you’re like us taking it easy until the busy life rushes back to us lol.
Ill be honest off the top of my head, without knowing your age of bike or its carby / efi etc, but i know full well:
GTR digital displays don’t play nice on bikes with naked harnesses as wiring changes slightly and they have their specific ECU or CDI’s incase of carby . Trying to use a digital display from lets say GTR to 2001 Comet with manual clocks, we need the speed sensor and the GTR’s whole wiring trunk & CDI, just to make sure things run as they should without trying to cross-breed stuff too much, some cases the dashes will go up in smoke if done wrong, seen it with my own eyes lol. This info is based real hand experience with my 2 bikes one is Comet , other is GTR
Ofcourse EFI dashes aren’t backwards to Carb’d bikes, so i’d pray your dash unit probably has a harness fault to check , as carby dashes are getting rare to get lol. KR isnt making old ones anymore 👎
Let’s start with the carb so that this huge thing is out of the way, we all dread going to it but needs must sometimes!
– > check your gold discs inside carb mouths are fully shut when the throttle is shut or look out for possible “notching / grinding” feeling if you tried to force the carb throttle shut even more.If it doesn’t twitch if you tried to force the throttle shut, then gold discs should be OK. If the gold discs were not shut, even a small amount of air will leak in to the engine combustion ==> revs go up!
Any situation concerning high revs is almost always mystery air entering the bike in some way
So with the carb investigated, clean its jets , pilots especially make sure you can see the holes or shine a light thru. The pilots can gum up easy when fuel is bad , so the revs again will shoot up = leaning out effect because less fuel has entered the bike combustion cycle.
Carb done ? Be very very religious about your intake manifolds, make sure they have no cracks and the “manifold” o rings haven’t looked crushed or old (otherwise i’d recommend changing them if they are too old , they may sneak air in which leans out the fuel thats about to enter pistons.
it’s these ones here.Intake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
Next up, go inspect the airbox for anything suspicious that may sneak air in (eg. cracked mouth openings etc, filter not sat properly etc, loose clamps)
On the choke side, check your carb rails where the choke slides across, u will see the plunger come out (on) and go back in fully (off) , or else check cable isnt trying to pull it. riding on choke no good for piston rings , i might add.
If we deal with the carb and intakes properly, then it will ride better , see how she runs then we go from there to attack other things .
I have a GT125R 2015 and the exhaust end can i have ordered is an sc-project crt, this exhaust end can is straight through, what would you recommend? should i get the 90 front and 92.5 rear main jets or bigger. also the exhaust can has no baffles with it.
You will loose the intial torque that you want when taking off, the baffle should be inside , and a baffle with a hole size (inside or out) of a 10p size, is a good sized hole. HUGE HOLE baffles are almost pointless but still better than without 😉
Fuller size cans do better than shorties on any 4T bike if im honest, ive found out the same on both 125 n 250 hyosungs, No baffle = it will scream more to get going at the same speeds sometimes.
90 and 92.5 is enough for 125s.
Then follow this tutorial below (it improves ur 90 n 92.5 in top gear, also 4-7k rpm flat spot fixing)(so extra mod)
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
I’m a bit of a novice with my multimeter but will give it a go.. do I test each component while engine is switched off but ignition turned on? Or will engine have to be running to test ohms?
For ohms testing , bike is turned off (key out), unplug the connectors and probe inside their own pins (any order)
Stator 3 pin yellow under 1 ohm on the meter (the lowest) => probe pin 1 and 3 , then pin 2 and 3, 2 and 1 , all 3 combinations should have the same figures.
Stator 2 pin blue/green = under 200 ohms on meter
HT wire of coil (red meter) and frame (ground for black meter) => under 6,000 ohms.
That should be it.
the only test while engine running is the stator yellow plug telling your meter its producing 80v -/+ at 4k revs ish , 85-99 is the optimal range as per service book in AC
Regulator itself also depends on the effeciency of the stator , since they go in tandem anyway.
Hey Mick 👍
We use huge regs that are mosfet based than basic shunt tech, you are right to assume the hyosung ones are as lethal as they come lol. You will see the regs at shop pages.
The regs I get from supply chain are off Kawasaki ATV’s mainly, 15v limit, 3 phasing stator, however i can say my own reg has been good for many years. I just make sure it fits the bikes listed & is intentionally large.
Electrosport in USA isn’t too bad either, i have it on one of my other hyosungs.If you’re fancy, you can get the Shingden ones which are common thing to do on the 650cc hyos, though wire bridging may be possible without the hyosung-harness kit that comes with the reg.
Conside the coils should be under 6k ohms from HT wire to frame or replace them, the stock ones will annoy you once they start to add up resistance, even while its hotter running.
HT Caps are made by Golden (china), switch to NGK and call it day 😉
The spark plugs should be new but it is possible a bad carb or coil will foul them up and it means new ones again. Don’t touch IX-Blue plugs ever, the hyosungs hate it. Use platinum ones (laser) or the stock copper ones.
Last shout, only because its part of live ignition system, stator yellow wires must be under 0.7 ohms (no more at all) each wire must be identical. (3 pin) do this when bike is turned off ofcourse.
Otherwise it should be about 80v strong AC at around 4k ish revs.Stator blue/green plug = 100-120 ohms .
As you go through the cleaning process & testing the initial stuff above^, from there then we shall see what else it needs or hopefully not.
You got this 🤺
Hi, Been lurking for a while and decided to sign up, currently have a GT125R but its currently in for repairs at the moment, would like to just say appreciate the effort Marcel puts in to keeping this place alive and answering questions!
Welcome fella, good to hear the feedback! – one of these days in march and summer there will be a meet, so maybe we might see you when your damsel is ready! 👌🤺
Moved to Technical.
Yes you are correct for the 125 it is 90 front and 92.5 rear as an upgrade.👍
More about that here
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
I’d be careful also to not force the jet in to the tube unit as its threads may change for good (soft brass)
for mikuni bds26 jet is 9mm tall , 8mm round head, should be m5 thread
I can’t find any screw holes for the bobbins, I’m thinking about having a couple of bosses welded on, but to be honest I was looking for an easier option
I’ll be honest, if the swingarm comes off, re-paint it and the bike shall thank you lol. Hyosung uses a lot of paint on plastics, tank, and the frame but swingarm tends to get patchy much sooner,
alas… salty roads in UK though lol. It shouldn’t bother you much if bike doesn’t see the rain everyday where you staying now.
If your GV has a swingarm taken off the 650 GT, but usually most 650 GV/GT will have holes under the swingarm to screw in aftermarket bobbins, which their size should be either 8mm or 10mm threaded.
Does your bike not have the holes ? Could dave you fabrication work to get hole spots welded on lol.
I’ll be looking to do it another way similar to what the 125s have (replacement adjuster block with intergral bobbins) , i’ve been thinking about it the past year as a new mod.
87.5 Front / 90 Rear = All 125R / RC
Some more reading on changing jets below:
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
Have good inspection on that bike, sounds like engine internals need attention for sure, as rare as 250s are becoming in UK, I know full well i cant take chances on what i own and maintain as best as i can
welcome to the forum 👍
Absolutely stunning! and the scenery, looks like a good spot for a boat ride in that heat while the bike stands there looking pretty lol.
Would you be doing the whole body purple ? That would certainly pop. (hmmmm, cadbury purple is yummy too)
As for the fender removals, the seat comes out , if you get the wheel off you sure have room under the bike should you want to move the plastics around, the best shout i can say is to change the bolts to some stainless variants.
Goes a long way, less fighting with the bike over seized bolts in some places, ive made sure ive got rid of every cheap external bolt i can see lol.Welcome Daz,
Dare i say, you wouldn’t like to be in UK right now lol, it’s hella wet and most of us aint even riding out that much , hell my GTR will go on a hiatus soon and will just ride the naked comet for short winter sprints, thats it lol
Hope the weather is better over there! Sunnier than it should be lol.
Check your float levels, so that the carb isn’t overfilling itself , to the point it will leak out of the top pipes near diaphragm covers
The T piece is something Mikuni does but can’t the closest Hyo part number i can find is:
13357HG5100 = KR Motors America appears to have it in stock, so can you ring your local garage where you live to ask KRMA to send it to you or dealer for pickup?Similarily Yamaha does this on their XJ700/900 bikes in the US with a part number of:
1j7-14988-00 ===> I must warn, i am not able to verify if this is brass or rubber T (which we want), so best to ring up your local yamaha garage for confirmation.hope this info helps , good luck. I think i will get a few myself lol, i do fix a lot of carbs now days but the T is rarely touched by the owners of bikes.
I got your email and replied, Printcutgfx in UK makes hyo stickers for me when i want them too , i think they can send it to your location as they have an ebay portal too.
if not, message me for actual genuines then ill see if it is possible to get them from KR
Hello Marcel, Checked all clutch parts but found no obvious damage, wear or out of tollerance parts. Plate 1 (7) are 2.97 mm, plate 2 is 3.48mm so well above the minimum, steel plates all flat and no warping or burn marks. Clutch release bearing looks fine as well as do all spacers, the basket does not show any damage or marks. Think I need to start looking at the gearside, may be the shifter forks or a bearing. Lost of work of course as I need to take the whole engine off the bike for that. Bike has done 8000km (5000 miles) and has had regular maintenance like oil and filter changes. If you hear of anything else to check please let me know. I will update as soon as I have time to disassemble the engin completely and check all parts.
Before diving to splitting the motor, also check the springs also vs the service limit?
Check the actuating arm (where cable connects) is aligned according to the cartoon diagram in the books (so clutch is actually disengaged, rather than being slightly pulled even though its neutral)Grasp the hub of the clutch with your hand and see if it “moves” even the slightest, but crank bearings should be ok, as 5k miles is a young machine
When re-testing the bike, see if the clutch makes any noises , this time your ears are at the basket during idling, and also hearing & feeling the engine while riding , the wind is noisy but see if you can pay attention only during gear changes?
