♠️ M77
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Welcome to the forum, man that’s a very clean GT Naked. We don’t see too many of them with that new facelift front in UK.
It should freely rev to 10k revs max , as that would be about 90mph which is about right for an EFi bike without redlining it (They don’t like being redlined anyways for too long except simply to overtake a slow car at high speed)
Perharps also consider it’s still under 600 miles , so you’re still “running it in” meaning go very easy with it for the 1st 1,000 miles.
Take it in for service at 600 miles as per service manual, they will check the clearances are good and compression is great . in USA, you should still have access to E5 grade fuel, use that forever. E10 isn’t great on cars or bikes in UK anyway, it’s a wasted economy so to say!
I have a 2002 GV250 I managed to get the carb off the bike after a lot of yanking, pulling, and twisting. Now it is time to re-install the carb on the bike, any suggestions on how to get it back on the bike given the very small space to work?
Hey, take a look at this rough topic i just created below
[Tutorial] How to Remove & Re-Install the GV125 Carby | GV250 AirBox
Hope this helps you and look after those intake pipes, they are now the most difficult parts to get! (Korea stopped making them)
Can you attach a picture of your current cdi so we see the plugs , some CDI have 3 plugs and some have 2 and some have 1 (too rare as usually thats for a GA cruise but korea can surprise us with their cruiser variants of bikes)
GT125/GT250 carby bikes are always 3 plugs.
As per Simon, he is correct on both replies. Nothing to worry about here , they face the road indeed.
However….
If you have a carb bike, please check your carb top diaphragm covers must have 2 tubes joined to 1 long long long tube that travels to the rear of the bike then faces down to the road.
Carb Bike has 3 overflows/breather zones mainly
- Fuel Tank – As per your picture and simon’s confirmation.
- Engine Overflow/Breather – As per your picture & simon confirming it too.
- Carb Unit – if unsure take a pic of BOTH sides of the carb (front and back)
If online, then try Demon Tweaks UK . Good source for tyres and i use them for various bikes.
Michelin Pilot Road (2 to 5)
I find 2 being the longest wearing and just as great as winter tyres too (remember no tyre is snow proof, so caution the icy winter seasons!)
However, Michelins always come out on top, i try not to be biased because my fav other tyre is Bridgestone BT92 , (very sticky tyre!) God i miss it but its harder to find, you may end up having to ask whoever is local to you to import it that does bike tyre fittings on the spot.
Also try Michelin Pilot Street Radial (it must say “Radial” if getting a Street tyre than Pilot Road) , avons displace water sure , but i don’t like them as they slide too much in wet and believe me i’m not always calm when i go to the countrysides to get a bit of a lean down so i don’t square my tyres off lol.
So yeah, unless it’s a matter of preference , opinions may vary 😉 , take what i say with a grain of salt too and this is all from my fav experience wth them and i won’t look back;
- Pilot Street Radial 🤍
- Pilot Road 2 🤍
- Pilot Road 3
- Bridgestone Japan BT92 🤍
- Bridgestone BT23 (dry days only, as winter they get skittish)
- Bridgestone HYPERSPORTS BT016 PRO BATTLAX (rode all wet winters with them, they are great in summer but slippy in wet if you get too excited or go grazy with brakes, be calm in winter with these and they will get you home fine) === My current tyre ATM
Factory size is 110/70 front and 150/70 rear.
Believe me, there is absolutely no need to go bigger and it’s overkill as half the modern small ADV bikes have 140-130 tyres already, so this 125cc is generous enough. the wheels weigh 15kgs each as i post them in general. Ignore people who say stick a 200 tyre on. If in doubt, just trust Hyosung who made the bikes.Hello, I was away for a few days, have you managed to sort this then ?
if not take a picture of the front carb , and behind it , it should have a long cable idle screw with a spring and washer going to a throttle “PLATE” that is under the front FLOAT BOWL (where fuel rests upside down) (aka. left side of the bike is all you need to be, don’t go to the right side of the bike)
I would screw in really gently as threads strip and use PUTOLINE Race Grease on “anything” that moves on the bike because weather wants to rust your bike every chance it gets and parts seize. Parts are for carbies are getting rarer now, so you want to look after it as best you can.
Hide your brake discs , –> wash bike -> dry up —> get ACF50 can —> soak the entire bike engine , parts in it, and it will thank you. I know , i said it too simple but a youtube video of applying acf50 on the bike exists by now. If unsure, ask and i will find an appropriate video.
Hey Lee,
A draft tutorial should be totally fine, i’ll do my best to send a rough copy as soon as the order is made and may even use your own videos to publish on the forum publicly to your credit to help other GV125-S owners indeed.
I like that you have helping hand should you need it but nothing like you doing it yourself fella , you got this!
I would not touch them whatsoever if it is an original bike that’s never had any mods or last keepers fiddling with it. Korea nailed it perfectly so much they don’t even reveal on the service manual how to adjust them, they actively discourage it.
90% of the time carbs just need a good old bath session with an ultrasonic man and a sessision with the air compressor man (as per service manual)
Rattle cans don’t always do it properly. So an ultrasonic bath + air compressor (these 2 together is a must) then carb will really thank you for it.This should be done on a carb wizard, as balancing will follow next and either the exhaust pipes of each engine is analyzed or sticking some meter to read A/F ratio at the end to ensure mixture is correct.
Too little = new piston rings soon (with this summer heat = very very soon)
Too much = a very moody woman to start, and poor riding in general.If you’re looking to improve the top end fuel, check this below.
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
If you are looking to improve the mid-range (4 to 7k rpm), check this below
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
Here is an old topic what may have some little wisdom to check certain things on the bike, while you are near the carb area and becareful with rubber intake manifolds , you will see why in the link below.
Hello,
Yes 650 forks fit 650 bikes no problem
However, if you have silver forks, use 650 silver forks because they use the grey TCTC Calipers.
If you have black 2018 forks, then use black 2018 forks , due to the fact Hyosung upgraded the calipers to bigger black ones
Out of couriosity , what has happened to the GV650 forks ?
If you get any issues, reply here and keep us posted. We do have those Acorn Nuts and Needle Jets (NJ) at the shop pages should you need them
I must say to caution with them little nuts , they don’t take much to get snapped , i’ve been there myself!
Hey,
Do you plan to fit them yourself or are you getting a helping hand for it all or was the mechanic asking?
Sorry for slow reply today
I suppose I could make up some draft tutorial ? – If you see the shop page i have asked customers to email me pics of their bikes before, after and during instal, just to prove how much of a “swap & go” business it really is, assuming they have worked on bikes before and knew the process. Most owners fit the kits themselves , with the odd owner or 2 asking me directly for assisstance on a small thing regarding a sprocket orientation etc. (which way it faces etc)
Welcome Marcus , its really good to have you on the forum , i can see more owners are growing on the forum that own the newer version of the GV125-S EFi
As last year, there wasn’t that many on road. I like the look of them but i do have my heart set on the eventual GV300SA , that’s the one i want 🙂
You will enjoy the GV125-S EFi for sure, plenty of support here if you need us! Although the EFI 125 is Hyosung’s 1st ever EFi Injected 125cc , they have been doing carb bikes for 125cc until 2019 ish and EFI 250/650 since 2008 , so other members will still chime in for whatever crops up.
Though, if you bought it new, you should be okay under a good care of your dealer. I say “good care” as some dealers/garages around the UK won’t touch Hyosungs which is silly so this is just a heads up! keep your warranty papers intact for servicing incase sinnis needs to send anything as they are the main importers of the bike (Real Hyosung UK through them as proxy)
Enjoy the summer !
Let us know the results of the compression test results (after the engine is hot, and crank bike full throttle with both plugs out) but tell the mechanic also cause sometimes they leave one plug inside causing bike to fire, the spark plugs must be physically out of the engine not just disconnected from the HT casps.
Just adding to what Tom said above ^ , go with what he says , even clearances pay dividents (valves too loose or too tight gets worse when bike is hot) thus , alas , the speed woes happen as valve head isn’t being 100% efficient.
If we can deal with the engine from top to bottom , before we can focus on any parts outside of the engine (whatever is under the frame responsible for keeping the bike going)
Clutch may be next , have macro meters and vernier calipers ready to measure the clutch , HP losses can happen on heat fatigued old springs and worn glazed up clutch plates , hence Korea says in their service books clutch should either be “looked at” or “changed” around every 4/5k due nature of the heavy bike with 2 hungry pistons , it can tax the clutch a bit.
keep us posted!
I don’t suppose you know of anywhere I can grab a service manual for the GV125S-EFI?
It will usually be supplied with the bike by Sinnis (the exclusive importer of Hyosung GV125 now/GV300S)
However, they will provide the “very least” an owners booklet and the service manual stays with the garage (whoever the garage is responsible for fixing your bike as per warranty schedules) ,
Being a brand new bike, i don’t expect drama already as long as its looked after , but ofcouse shout in this website if you’re stuck with something!
It looks correct, i can’t see how that will stop the bike running to be fair.
It sounds something else has gone off during the assembly / disassembly of the bike.
Also idle-adjuster is under the coils or it is near the front carb if korea put a short one.
I can see fuel in the filter, it is flowing. So that leaves out the tap & pump.
However, check vacuum leaks with a carb cleaner by spraying the intake pipes and check air pipes for any splits or kinks or bends
Also Hyosungs don’t like E10 , the carb 125s will usually make sure to punish the owner eventually when it keeps using e10. So if you have e10 , get rid of it and be ready to clean the carbs by only ULTRASONIC or AIR COMPRESSOR —- (Rattle cans won’t do the job, they aint agressive enough)
Firstly, welcome sir 🙂
This may go over your head but please trust me, can you do the following below first
- Let it get hot for 10mins. Then do a compression test.
Tell us what PSI each cylinder is , on full throttle. both plugs out. - Can you allow the bike to get overnight ice cold (required) then wake up , do a clearance check with a feeler gauge by taking valve covers off.
Tell us what each valve says,
eg. Exhaust Rear (sprocket side) = 0.26mm
eg. Exhaust Rear (cam chain side) = o.28mm
eg. Intake Rear (each side) = 0.13mm
Repeat
This
For the front engine.I will upload more manuals on the site when i get time. In meantime, checkout manuals lib site for “GT125 Service Manual” and follow instructions on how to test compression or clearance or let a garage do it real quick and get proof on paper. Don’t trust their lips.
- Also,
While at it, check your clutch plates with a VENIER CALIPER and measure thickness of each plate.
Also check how long the spring is (standing) , don’t compress a clutch spring. Eg. springs x2 35mm and other springs 32mm long etc..
What i said above, is critical to hit the 80 mark, otherwise the bike won’t do it no matter how tuned it is. So to save you money buying random things. Lets make sure the engine itself is healthy with the above checked.
Please report back and let us know how you get on!
