♠️ M77
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Welcome to the site fella,
Before we get to the electronics, lets go straight to the core engine itself.
– How old is it ? Total lifetime miles?
– Have the valve clearances been done in the last 4000 miles (very very, important)
– Have you done a compression test ? = Low psi will make it hard to start & generally runs rough sometimes while riding.Hey, i mentioned similar comments on facebook you posted also.
I can also add that via private discussions with owners with these bikes, they are capable bikes!
The only complaints so far i’ve heard (no fault of the owners),
– 1 ex keeper messed with the coils and plugs so bike is temperamental, so atm i am helping the client replace those parts as Sinnis will not get involved as he isn’t the original owner, so warranty has been void. All because the ex keeper put wrong parts!
– 1 abroad has had to change the air filter as it was drawing back some speed.That’s about it as far as i am aware.
1 Owner has even said the bike pulls better with some upgrade clutch parts i have sent him , he has a 520 kit too.
The real draw back for us here in UK i guess is the top speed is a little lacking, hence i started doing 520 conversions for them. The stock speeds are usually around 65 ish , so after the conversion process they now peak at 80 which is more than sufficient without sacrificing the acceleration (which is also key to get the bike going as soon as lights go green)
All in all , I like them , i hope to get the GV300 version for myself.
Tom has been helpful in your diagnosis , so go with what he says because i deal with wayyyyyy worse hyosungs and i usually have them running within a week. I am in yorkshire, so you ain’t to far fella. But don’t race to bring the bike to me just yet since i have faith you will be able to work on it and your hands are free labour.
Hey, if you crack this thing, you will be half-way being your own self-hyosung wizard!
I wont lie I wish korea spent more time in the electronics sector , but i can’t entirely blame them as my own inlaw has a new 2021 Jap bike thats flashing EML light and has been happening since the rains of 2021. The weather’s elements can be unforgiving, thus any bike i own personally i am usually ocd by;
– re-wrapping the harness all over tight , tight , tight.
– using “Suzuki Harness Boots” to hide any plugs subject to water attacks
– using ACF50, in every terminal, just a tiny bit , even if one bike doesn’t see rain , but least i can aid in preventing some form of oxidization. (Oxygen + Steel is a constant war, in of itself. but don’t panic, we have ways around these things to keep our 2 wheels longer)Remember if the loom is great (fixed or inspected by you) then this is the usual sequence to start the bike;
– Is Neutral ON?
– Is the kickstand switch bypassed (yes , but don’t forget to always PULL in clutch when starting, fake neutral starts are rare but can happen and bike falls to the ground!)
– Is Clutch Switch Sensor ok ? (Multi meter = ohms in zero will mean its dead if you squeeze the clutch handle lever on / off , it will mean the circuit is dead)
– is the CDI ok ?
– is the Stator Pickup coil connected? (critical) = no stator, no sparks.
– is the stator 3 yellow plug connected (not critical to “ignite” the bike)
– bike rolls freely (real neutral) (this is on you to make sure just in general)
– Solenoid OK? (it will make click sounds if its dying or needs replacing)
– Battery is 14BS? (OEM size for GT bikes of any CC)
– Battery is not old ? (Hint = just turning on the bike, the volt meter will quickly drop from 12.8v to 10v in matter of seconds) (Replace it.)Garages have a special yuasa analyzer that can check your battery and their screens will either say “battery good” or “battery needs replacing”. They do this for free anyways.
– Kill Switch Red Button is “pressed down” ? (towards you)
– Start Button isn’t broken?Press start ==> check plugs for sparks ….
very Dull yellow sparks = Replace battery (common, winter is usually the harshest time for them), or check coils (common) or plugs (faulty plugs) or fishy HT caps ? – ensure plugs are CR8E ,dont buy LASER PLUGS until it runs. Its cheaper to run through basic CR8E for now . Don’t bother with Blue Box Iridium IX as the Hyos don’t like them much but yes they will run with them.
Hope i have made sense!
Welcome Stu!
Post a picture of your ride here -> https://hyoriders.club/forums/topic/owners-photography-thread-new-rider-show-off-your-ride/
To answer the 520 part, yes what you see on this website’s store is generally self-fitting (meaning yourself, some correct tools and skill level depends on your confidence to take certain things off and put them back exactly the same way back) but a garage can definitely do it. However, i would caution and watch what they are doing, it has come to my attention via private communications my clients have had mechs take silly shortcuts or can’t be arsed to work on hyo cause its Chinese (really ?) and they half-arse the job , thus meaning what ever mods they fitted became quickly pointless if the bike behaves worse than it did before.
Speaking of behavior, let’s assume you are a brand new owner and bike is total blind buy (no history whatsoever or last owners lied etc), so to make it a good “standard” bike , can these be done at your end (trust me, the hyosung will really appreciate you for it)
– Full tank flush and put e5 , cause e10 is from hell.- Carb = Ultrasonic clean , Rebuild it (with this kit) , do the slide mod (click here), check jets are okay (here)
Standard Jets are OK, if there is no air intake mods or exhaust mods. I am assuming this bike has zero modifications? - Do not mess with the mixtures. Only thing you have to do is allow the carb to someone ultrasonic clean it, because sometimes rattle cans don’t always get the job done or be ready to go through at least 4L of rattle cans just to really assure the carb is cleaned, remember it has many holes inside , not just jets.
When i deal with customer carbs , i use air compressor (as korea advises) and liquid cleaning ofcourse in a bath. Neither a garage should not mess with the mixtures UNLESS they have experience with a BDS26 carb and a Hyosung GT125. Just because they know other 125s doesn’t mean the hyosung will behave the same way inregards to them messing with the mixtures - Go (here) and look for the picture of float height, make sure it is certain. Also, read that topic i just linked in this sentence as it has some back and forth chatter which can help you diagnose other potential running issues. The lad in that topic may have a 2003 Naked 125 but they have the same carbs and same engines.
- Before opening a carb, make sure to get “JIS” screwdrivers. I can’t stress it. Normal UK Made or Chinese made philips (+) drivers WILL ALWAYS ROUND IT OFF. Sorry for the caps , it can get frustrating later so JIS screwdriver set is a good must. I use a set fron USPRO , they are great!
- Head over to the shop of this website and get yourself some stainless bolts! For both top and bottom. You won’t regret it.
- Just looking around the hyosung it is almost a consensus for everyone now to use stainless fasteners or titanium all over the bike. Pricy? Yes. But its not just for looks , the maintanenance of the bike will be a lot better in general.
The only thing that can stay standard is the axles for the wheels and mono shock linkage parts. It is not a good idea to go stainless on axles. I dare not digress. - Putoline race grease (apply it on ANYTHING that moves) –> except Wires! & brake discs!
- Wires = Every single plug that exists on the bike –> use a little drop of acf50 on them. This every biker’s “must” do list, UK is salty and weather likes to rust exposed things given the chance!
- Copper Grease = back of pads , on the fork bolts near the bottom of the bike, mudguard bolts, things that look like they will seized under constant water attacks which is usually the areas where wheels are.
The is NO need to apply copper slip on the AXLE BAR NUT on the rear wheel. No need
Apply copper grease on ALL fairing bolts or Go Stainless.
Moving on…..
- Clutch = Overhaul it (especially if its beyond 4k miles from new, it tends to be forgotten about. HP passes through the clutch before spinning the back wheel, so you want the clutch to stay punchy)
- Gearbox and many parts inside the motor = Use Motul 7100 or Silkolene Comp 4 forever. These 2 brands forever. No matter what sales man tells you in his bike shop, they are not that slick to sell crappy Castrols (no pun intended). The service manual says use costly oil if you can (premium) if bike has a harder life which the 125 generally does compared to a 650.
- Compression Test = A garage can do this within 5 mins , please get it done and tell us the figures.
- Clearances check = A garage must only do this below….
– – Open the valve tops of each engine.
– – Open the “Timing Viewer” hole , he spins to “F” mark = Front Engine
– – Spin 10 times the crank.
– – Put a feeler gauge and write clearance values for front engine. Dont pay him if he can’t provide this info.Repeat for rear engine.Come back to this forum and let us know the clearancesBelieve it or not, clearances are almost 50% (if not the main cause) of poor starts, hard to tune the carbs due tight valves, slower top speed if valves are too loose, engine is generally louder if valves are loose in terms of clearances under heavy load, and it goes on. Good news if the clearances are good, then you don’t have to worry about costly garage bill to do it!
I could go on , but you have only just joined so sorry if this overwhelmed you, knock off what i said above ^ , one by one , and if she is a super well behaved standard bike, then pimping her “mod wise” will be easier to advise on what benefits what and to save you some cash where possible. Some silly mods on in the internet are placebo effect (like the infamous CDI cheat on Hyo 125s which is silly but a stronger electric system will be noticeable instead, the CDI isn’t restricted whatsoever, so this is just an example)
Hey Tom,
That’s fine, if you ever need a fresh plug, just let me know!It’s okay to admit you have a thing for Hyosungs haha, if interested i do have a GV250 frame if you want it , it has no number plate as i lost it. But no V5 as it was a barn find . It is HPI clear , so if you need the chassis number i can aways provide it and do your own HPI checks. Offers on the frame are welcome! Just be happy to see it being made to good use for someone else 🙂
The air filter box, if you take another pic of your situation, this time a bit further way from from the bike so i can see what’s not fitting for you or not.
Part metal and part rubber manifolds is not a bad idea. Keep in mind, GV125 Aquila is easier to make inlets. And the 650.
The GT125s & GT250s & GV250s have all different inlets , trust, they will not cross breed and are harder to copy due to such awkward shape and how the airbox is 100% accurate straight under it
The 250 box for GT is even factory tilted at the bottom! I digress!
Can you get some pictures of your situation if possible, so we can see where you are stuck exactly , as it should go in the same way you took it out.
However, i would caution not to stress the manifolds, korea doesn’t make em any more and be ready to fork out ££££££s just to even get a decent half -cracked up one .
Hey, I am really sorry about the golden drain plug!
Do you want me to send another? i sent the wrong size!
Korea uses the same airboxes for both the GV125 and 250. The air filters either white or red, always come with some 5% of error margin of accuracy but with some force they always fit. I believe the struggle was intention to keep it air tight once it finally goes in!
Sorry i delayed,
Get some pics of the wiring harness plugs and your cdi unit, also show us the part number of the cdi , just incase its the wrong one (GV cdi instead of a GT one.)
Check these also,
– Primary and Secondary resistance of the ignition coils (WITHOUT the HT Cap attached)
– Check Resistance of the HT CAP on its own (up to 10k ohms)
– Check resistance of the stator PULSE (pick up) sensor (this unit determines sparks, if its too low or dead, no sparks will happen)
– Check Handle Bar clutch switch (if its bad, no sparks here either)
– Side Stand Switch (bypass it by joining wires, highly encouraged) (make sure to waterproof the wires safely!)I have done about 50 miles in this barcelonian style heatwave until the country cooled down again to 7c! – It has been really nice, so i can imagine you and Rosie made a nice picnic style trips out of it. April is around, so we shall expect some consistence 15c weather as it rises up to the summer 20s.
It was nice to know there is a garage out there that isnt going to treat the bike like its chinese and take silly shortcuts , sometimes its what other clients tell me and their bikes behave worse due to mechanic errors. So well done on you for being hands on , i suppose working on a “hyosung” will make you a bike wizard that’s for sure haha!
I have a GV myself and i’ve been thinking to make it a bobber style similar to the upcoming GV300SA 2022 , but ofcourse it means no screens. I wouldn’t mind the wind in the summer! – Winter time, means i will have to wear some kind of heated vest. Function/Practicality vs Looks is a debate i have with myself each day. However , short screens aint too bad , similar to the GT250P model hyosungs, i might do that , if i have a batwing , i wouldn’t be any faster as there isnt much aerodynamics vs the wind, then again im not a racer.
The bike looks good without the screen sir! Nice photo
Hey,
In my experience without trying to follow Korea’s english. I try and keep it simple.
– Legs off. Drain oil. Inspect hardware.
– Change seals , if burst.
– Sort the hardware back together, add the total oil it requires, usually 10w as factory 5w is too thin.
– Fit legs back on the bike. Test ride gently, go through some speed bumps and see how it feels leaning around, increase speed, see if it judders or not.Then job done haha
hello everybody im new here and i was wondering if anybody can help me out with the pinout of a 2006 comet gt 250r cdi unit? please and thank you.
Hey welcome!
What seems to be the issue with the CDI unit ? – These things rarely fail unless electrics spiked out to die (ie, fishy coils , battery, stator, reg) .If the fork oil is drained from the tubes completely, i would go with the total amount to refill from the service manual. Unless somehow its leaking elsewhere (causing amounts to drop?)
Did you get the new parts from this site or somewhere else ?
How is the regulator ? How is the stator ? = These 2 parts (if not in spec by meter readings) will definitely make them weakest links for ignition systems and charging systems.
Stator is part of sparking system due to the fact it supplies energy (yellow wires) and communicates to the CDI how fast the flywheel is spinning etc (blue/green wires)
So the stator must output least 70v at 5k revs max. 80-90v is optimal. Max is 99v. The korea OEM stators are infamous worldwide either 125 or 650 or 250, most owners upgrade them. There isnt much positives about them.
Same goes for the regulators, it is usually the 1st thing we change electric wise for something better.Reg will say 14v both idle and 5k revs = any less than 13.5v (whatever revs) = must change. Manual also says this.
Hey, even Korea says to check bolts every now and then, it seems like they knew about this. While you at, you can be OCD like me and make it mission to replace every bolt with stainless steel except the axles and shocks.
Coppa slip is good in certain places such as panels that hide the coils and batteries.
Michelins i usually get them from Demon Tweaks, trade supplier but also open to the public, you may know them already, so give them a quick ring otherwise i don’t mind brigestones. Jap tyre! – I have some bridges on my donor GT bikes. They are okay.
Hey,
You can buy EGR blanking plates at the website shop above menu.Also, you can do this ….
Intake pipe 1 = hose.
Intake pipe 2 = hose.Run both hoses to the back —— > T PIECE JUNCTION —– Junction 1 to tank & Juntion 2 to tap.
if that was too confusing, do it how the Koreans did it originally below in a simplified way…
Yikes! – Before i could say anything more , how is it all going so far then ?
Expensive to replace but won’t stop me getting them if i was asked to , even if i have to scour the earth for some!
Much rarer than GT manifolds, it is wise for GV owners to do their best to treat the manifolds well.
Hey Rosie looks good! – I see you have took my advise so we can feast our eyes on your bike.
Hey , i don’t really socialize too much on FB unless answering queries , i am getting old myself , but i know half the members on here don’t even use facebook to chat about bikes (in this case doing journals) or posting pictures of their outings & excursions with the bikes, this site may just be about the “closest” thing to some kind of “social network” should we say!
Tom , i dare not show my age but i have vague memories about hearing that song at one point as a much younger man lol.
@Zigger – “As with any new girlfriend you have to start spending money on presents, ” —- You said it right there, either its a woman or a bike, once our eyes go left , so does our wallet and we usually don’t think to get it “right” till way later haha! –
Tyres do take a lot of my budget every year as i usually spend best of the best (michelins) i guess but i do a lot of miles each year , so its unavoidable. Just as is pads are always going to get change probably twice or thrice a year!
Some modifications = spend once, smile later, now those i can live with.
They did exist but much rarer though! – It is now common they are now 5 speed, as is the GT125 bikes.
It is the GT650 and GV650 still to this day share the same engine but the GT650 has 6 gears. (Sometimes the GV does!) – Also depends on the markets Korea sells the bikes to.
Don’t worry though, the 5 speed gearbox on the 125 is more than adequate for it as the 6th would be like some kind of overdrive gear.
- Carb = Ultrasonic clean , Rebuild it (with this kit) , do the slide mod (click here), check jets are okay (here)
