Topic Tag

gv250

Fuel System Problems and Question about GV250

Hi all,

My girlfriend just picked up a 2007 GV250. We knew when we bought the bike that there was an issue where when you twist the throttle, it dies. It was too good of a deal to pass up on, so we decided to give it a try as her first bike.

When we got it home and started working on it, I figured it would be a fuelling issue, so we took the tank off, and there only appears to be one carburetor. Everything I saw online for these bikes showed that there should be 2 carbs, so I’m wondering if that was a factory thing on some of those bikes, or if someone has swapped this in since. If anyone happens to have any diagrams showing a single carb, that would be much appreciated.

The issue with it running does appear to be fuel related, as I did get it revving slightly by playing with the throttle adjustment on the carb, but it still does sometimes die, and when I do get it running sometimes it won’t idle now. Also when it is sitting not running, there is sometimes fuel leaking out of the intake side of the carburetor.

If anyone has any advice on what to try to make this work properly, I would really appreciate it.

Thank you in advance!

Kevin

GT250 EFI DSpec Stalls at Idle after Warm Up

I own the above mentioned bike bought second hand from the original owner who had purchased it in 2013. When I bought it, it was still under warranty with about 3000km on the clock. It is important to note that this version, the DSpec, has some minor differences in the number of sensors than similar GT250’s of that period. It is a twin cylinder equipped with Delphi electronics. The bike, which is always garaged, worked flawlessly for the first couple of years but after that it had started to loose power erratically after warm up. This was happening after about 15mins of starting from cold. From time to time I was also getting error code 132 intermittently which indicated problems on cylinder one. When the O2 sensor was inspected it was found to be covered in soot. Because of this I had assumed that the problem was limited to around cylinder 1. I replaced the plugs and high voltage cables and also swapped the coils and the O2 sensors around but the problem did not seem to change or move. I also had the injectors cleaned up by an experienced bike mechanic. I was also lucky to find a nearly new ECU which I could purchase at half price, but even this did not improve the situation.

Finally I decided to replace the coils which solved the problem completely.

Unfortunately a few more years down the line I am starting to experience a similar, though not so drastic situation so far with the bike starting perfectly but after warm up it starts missing occasionally at idle and if I stay at idle long enough the engine stalls. I don’t feel any loss in power when I am revved up.

Because of this I am starting to suspect the coils again even though these are no more than 3 years old.

Any ideas?

Regards

Adventures With Rosie

Well the following nonsense is coming out of something Marcel said last week “You could post a forum journal on the front page, incase we make threaded replies to follow your outings or garage workings”. I can’t see where or how I do that exactly – hey I’m 62 years old, we didn’t have social media in the seventies, no internet, just great music and lots of fun, so if Marcel wants to move my bloggy blatherings somewhere more appropriate he is very welcome to do so.

So this is Rosie, my 2016 GV250 EFi, that had just 2,785 on the clock when I bought her 17th December last year, and is now showing 3,190 so she’s done 3 times the mileage in the last three months than she did on the previous 3 years. And you know, I think she rather likes it.

As with any new girlfriend you have to start spending money on presents, so the boring black air filter covers have been replaced with chrome and, more practically, a centre stand has been fitted. I was pleasantly surprised that the 5 minute job as demonstrated on YouTube (see https://www.youtube.com/watch?v=jzljlX9CyHI ) took just that although my garage floor was a lot more cramped, and very much colder, than lucky old Two Wheel Exploits in Melbourne. With shipping the stand cost about £70* from South Korea, and I’ve seen these on eBay for £115 – £125 so I’m happy with the deal.

I think I’ll probably recoup that cost the first time I do my own oil change, plus I can fill the tank on the level without risking a crotch full of Ethanol.

Next bit of bling was replacements for the missing front fork top covers. Now it annoyed me that I hadn’t noticed that these were missing when I inspected the bike, the headlamp has been replaced with a unit held on by two clamps attached to the fork tubes. Now these clamps are either stopping the front forks from working, or are scratching the tubes any time the forks depress, and they are certainly stopping the refitting of the chrome covers.

Front forks with the offending headlamp brackets

So when it became apparent that the headlamp couldn’t be refitted with these clamps gripping the fork covers rather than the forks an order had to go back to South Korea for a proper headlamp mounting unit, which fits into the lower fork brace. Oh, and a new headlamp housing to fit on the mounting. What’s the betting I then need a replacement headlamp lamp unit to fit in the housing that goes on the mounting?
“And the foot bone’s connected to the leg bone.
The leg bone’s connected to the knee bone.
The knee bone’s connected to the thigh bone.
An’ that’s the word of the Lawd.”

Just in case anyone’s thinking “you’re wasting money on bling! What about brake pads and tyres and…??” rest assured they have all been checked and are perfectly in order for a bike with just 3,000 miles on the clock.

BTW: If anyone knows of a really cool looking and powerful LED headlight unit that fits into the standard GV250 EFi 7.6″ headlamp housing, then I’d be much obliged.

Once these geegaws have been fitted that will probably be it for bling. For a while. Although I’d love to fit a lamp rack with a pair of fog lights. And of course I do need some saddle bags for the gear I have to tote too and from the office.

Meanwhile I’ve been trying out my ‘A’ roads route to Northampton that misses out the M1. Although hampered by a light spot of rain I had a very enjoyable blast along the A6 today that certainly exceeded 60mph and may have reached the dizzy figure of 70+mph. Rosie certainly seemed to be enjoying herself.

Why have I called her ‘Rosie‘. That’s in honour of Bon Scott, Malcolm Young and of course surviving brother Angus, who on the 16th May 1978 blew my ears off with one of the loudest sets I ever heard. Like I say, we had a pretty good time in the seventies. For a 250cc bike there’s a ‘Whole Lotta Rosie’, and she’s quite a ride. Although at 27 stones she’s a bit heavier than the original
“Doin’ all the things
Doin’ all the things you do
Ain’t no fairy story
Ain’t no skin and bones
But you give it all you got
Weighin’ in at nineteen stone”

‘ave a gud ‘un
Zigger Zag

GV250 Chrome Front Fork Covers (Upper)

Does anyone know whether there were any changes to the Upper Front Fork Covers (Current Part #51881HJ8200) for the GV250 over the years? I have a 2016 registered GV250 EFi Aquila with missing upper fork covers (only noticed it last night after delivery – Doh!). There’s a good looking pair from a breaker not far from me noted as from a GV250 Aquila 2001. Does anyone know if there was a change in the part design over that time? Admitted, 15 years is a long time frame, but it looks as though there’s no change in this cosmetic feature on all the pictures I can see.

Many thanks
ZZ

2003 hyosung gv250 carb model – idles ok but wont go

Hello guys, i have a problem with my 2003 gv250 carb model, its having trouble revving. While stationary it idles well, and can take slow rev ups, however when i pull the throttle quickly the engine turns off. I tried letting it warm up a bit but it made no difference. When i try to move into gear it instantly turns off. The modifications ive made are iridium spark plugs cr8eIX, after i changed the plugs the bike worked well except for a little loss of power for a second at about 7k revs, later i changed to these ht leads (https://hyoriders.club/shop/gt125-gt125r/hyosung-spark-plug-cap-cover-gtr-gt-gv/) which is when the no go problem really became a problem. Has anyone encountered a anything similar? Or can maybe guide on how i can fix this?

[Tutorial] How to Change Oil & Filter on Hyosung GV + GT125/250 +R

Time for an oil change ? …One of the crucial things to stay on top of!

This short tutorial aims to show you how to change your oil with ease on the 125/250 twins (2001-2018) and let’s not forget the filter too!

This applies to: GV125 (01-2018) / GV250 (upto 2018) / GT & GTR 125 (03-2018) inc GT250+R too.

Personally, one of the other twins I own gets its oil changes every 1,000-1500 miles using Ester oils . I’ve been this way for almost 4-5yrs at time of this writing, the manual suggests the oil can be changed at longer intervals. This is optimistic to say the least, so i’ll leave that there. I know too well, oil acts funny around the 1500 mark tops (gearbox, clutch, false N’s, hotter, louder). The internet will send you down a rabbit hole, so my opinion? Use more premium oil marked JASO MA2 , Ester is good. Change around every 1500 tops.

Moving on, let’s prepare the parts & tools first…

Oil . Get 2x 1L Bottles (Bike needs 1.5L total)	Oil Filter & O-Rings (don’t skip filters!)	Drain Pan/Bucket (that can hold 3L+ of fluid.)
Torque Wrench (too crucial, you’ll see why below⏬)	Size 15/17mm Socket (12 sided!)(NO SPANNER)	Size 10mm Socket / Driver

Plus these bits also…
Pliers | Funnel | Plastic/Rubber Gloves | Clean Rags/Cloths. | Measuring Jug

1. Okay let’s go, Undo your filler cap first!
For stock caps – use a Pliers to open it (anti-clockwise).
For custom CNC Caps – We use either 19/21mm socket.

2. Go under engine & loosen the drain plug
For GTR owners, use a bar extension to aid you in undoing the drain bolt or just take your fairings off.
This tutorial was done on a Comet that’s all (& it needed a clean!😬)
⚠ Be slow to prevent this plug falling in to the bucket!

3. About those drain plugs…

Roads are salty, the stock plugs can’t fight off their bad rust. A seized plug will easily round off and you’ll replace more parts in the long run (strainer cap, o ring, bolts😬).
We avoid that by using a made coloured plug that has some weather resistance to it and it’s less prone to seizures.
Plus its magnetic tips are larger to catch those metalic shavings in the oil!
You will find them sold on here….

4. Finished draining? Close the drain-hole!
– Clean up under your engine
– Grab your torque wrench and set it to 15ft lbs max.
– Tighten your drain-bolt until your wrench clicks once.
⛔ DO NOT OVERTIGHTEN THIS BOLT.

5. Go to your oil filter cover next!
– Grab 10mm socket & undo the 3 nuts that hold the small cover.
⚠ Oil WILL fall out (leftovers from filter), so place a rag/cloth under the cover and potentially a small pan too. You will see why further down. Wear plastic/rubber gloves too. Ditch your old filter away 🗑
Hyosung Oil Change FIlter

6. Filter Cover Inspection & O Ring Change (Pt.1)

– Clean up your oil filter cover
– Check the spring is still good and not gone soft.
– Change the big o-ring (dress it up in oil first!⛔)
Hyosung Oil Change FIlter

7. O-Ring Change (Part2)

This part needs some more focused attention so we don’t damage the inside hole you’re about to see.
On the picture below, replace the o-ring that is sitting at the back inside the filter area.
⚠ Use a small hook/claw to pry it out , don’t force it. ⚠
CHANGE THE OLD ORING TO A FRESH ONE SUPPLIED.
Hyosung Oil Change FIlter

8. Next, your new oil filter goes in!

See the picture below? That’s exactly how it should go in.
The “hole” of your filter goes inside the engine.
Hyosung Oil Change FIlter

9. Close the filter cover!
– Once the filter is in, close the cover.
– Make sure the nuts are tightened to 6 ft lbs max!
🚦 Check the new Cover O-Ring is dressed in oil (a reminder!)
Hyosung Oil Change FIlter -

10. Done? Grab your oil (& measuring Jug!)
– Get a measuring Jug and pour inside 1500ml of oil in there (1.5L)
Not less, not more 😉
– No Measuring Jug ? That’s fine, as long as your bottle has volume-markers on it too.

11. Get your Funnel and pour the oil in….
Self explanatory here.
⚠ It’s messy doing an oil change without one, so I dare not digress.
Hyosung Oil Change FIlter

12. Close the oil filler cap!
Self explanatory here.
Just make sure the hole is clean and it’s o-ring isn’t damaged.
Hyosung Oil Change FIlter

🚦 Complete. – Idle for 60 seconds & turn it off!

– Start the bike and let it idle for less than a minute.⌚
– Switch it off. Let your bike sit upright temporarily⚠
(NO PADDOCKS. Both wheels on the ground)
– Check your sight-glass says “F” and oil level matches it.
– ^ Is your oil higher than “F”mark ? => Drain some.⚠
– ^ Is your oil lower than “L/M” mark => Topup/Refill⛔
– Finally, Check your drain plug is good & secure. 🚦

Tidy up & Go ride. 🏁

Questions? Fire away in the comments! 🤺

[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250

How to adjust/tune the carburettor slide needle for improved riding…

⚙ What does this do?
This modification allows the bike to reach better cruising speeds , via the slide needle adjustments. The throttle slide needle is what controls the main jet fuelling as revs go up & down while riding. This also eliminates some of the odd flat spots that happen during the 4k-7k rpm range , commonly on the 125s. In other words, for example if the bike starts to pull at almost full twist throttle , this mod will make it pull with less of a twist. Your bike should run better from 1st to 5th… fuelling wise…

👇 Before we start, This tutorial will assume the following:

You will do this at your own risk & without rushing.
You have better spark plugs (ie. Platinums) or older common IX plugs.
Your ignition coils & HT caps are sparking good
Your carb has already been upjetted (tap here…)
You have a performance filter (K&N, BMC, etc)
or if you have a white-stock cotton one -> cut its snorkel.

Tools needed:

JIS type screwdriver ( +philips style )	Large & long flat___ head screwdriver	Wynns Carb Cleaner
or … Allen Key (if using stainless bolts)	Size 7mm socket (sometimes bolts near the front are hex shaped.)
Watchmaker flat screw driver	Clean microfibre cloth

1. Go to the right side of your bike
You will spend most of your time here. Do 1 pot each time.
Make sure you do not get distracted as we are taking out small parts!

2. Unscrew the 1st diaphragm cover
Remove the 4 bolts that hold the diaphragm cover
⚠ You need to disconnect your throttle cable also.

3. Remove the spring & the diaphragm
Once the cover is off, gently remove the piston slide & its spring.

4. Inspect the parts for any debris and clean them.
Use Wynns Carb Cleaner to clean these parts including the diaphragm cover👍
This will stop your slides sticking between revs / gears & scoring to the internal carb walls.

[Tutorial] How to adjust Carb Slide Needle (Tuning) - Hyosung GV & GT 125/250

5. Unscrew the plastic plug holding the needle
Use a long good flat blade screwdriver for this and BE GENTLE – ⚠You do not want to damage this plug!

6. Do not forget the order of re-fitting back!
Keep this image in mind, when you refit the needle back. The order of these small bits is crucial too.
[Tutorial] How to adjust Carb Slide Needle (Tuning) - Hyosung GV & GT 125/250

7. Remove the E-Ring (Circlip) on the needle (SLOWLY!)
⚠ This tiny part must be removed gently with a small watchmaker screwdriver only,don’t pull it!

8A. See those 3 grooves on the needle? Read on…

A. The pointy end of needle FACES DOWN
B. Push down the “black spacer” a little bit.
C. Put the “E-RING (circlip)” in the 3rd GROOVE
D. Push the “black spacer” back against the E-Ring (Circlip)

[Tutorial] How to adjust Carb Slide Needle (Tuning) - Hyosung GV & GT 125/250

8B. Here is another view for you…

You want your “E-Ring” on the 3rd notch mark like the finished example including the black spacer being pushed back to where it was.
(Lowest groove with pointy end of slide needle facing down. The Factory set-up is usually the 2nd (middle) or top (1st) near the FLAT end of the needle.)

9A. Grab the throttle slide and look for this hole…
Make sure the hole shown in image is clear and proceed to 9B ….
hyosung throttle slide piston gv125 gt125r gt250r gv250

9B. Grab your needle too and follow the image….

9C. Slot the “Needle => first.” & its mini-spring on top.
⚠ Go back to #6 ^ , to remember how the needle spring goes in.
⚠ Remember what was said in 9A & 9B ^

10. Check the needle for free movement (a little bounce back)
Follow the 2 images for instructions/check up…

10B. Dress up the ring of the throttle slide with a temp oily coat.
It is going back to the carb, so you want to make sure the ring of the slide will sit firmly & create a good seal once fitted. This is to help prevent any unwarranted air leaks / external particle trapping.

11. Put the slide and big spring & close it up.

– Don’t forget to connect back your throttle cable
– Ensure the 4 screws are nice and tight (finger tight)
– Finished? Go open the next cover…

12. Repeat at the rear carb, what you did at the front…
Repeat steps 2 to 11^ on your rear carb.

13. Finished? 🏁 Check your lines before riding…🚦
Final check ups before you start riding , so attention to the following:

Air box clamps are still tight – check.
The carb slide cover bolts are finger tight (x8)
Throttle cable & choke cable are checked.
check your air lines and tighten them (preventing any vacuum leaks)

Done! this should have been a straightforward process , if you are unsure of something , just comment on this topic. Otherwise, go ride! 🏁

FAQ’s / Troubleshooting 🎳

My bike runs worse after I did this mod, what gives?
Check again the covers are tight so its not leaking air or check your intake system too (airbox area)
No air leaks, but it still runs worse?
Your spark plugs may need to be looked at, if its very sooty, clean it.
Also remember this mod expects you to have some better sparking than a stock hyosung does
It has new spark plugs, but still worse…?
If you have Platinum plugs fitted or the IX ones , but the plugs appear sooty…
You may need to investigate your HT Cap & Ignition Coils.
HT Cap on its own (removed) = 6k ohms on your multi meter it should say.
Ignition Coil = 6k ohms max when you measure coil HT WIRE and you bike FRAME.
Okay, the HT cap or coils are showing higher values than 6K ohms? Any fixes?
Replace them both. The stock ignition sparking parts can’t be user-repaired.
All Hyosung stock coils and their “GOLDEN” branded caps not great, another main cause of boggy runs on the 125cc bikes especially.
I changed the coils and HT caps already, its still worse?
Look at your main jets are clean and also investigate your pilot jets
The ofricies in the 125cc jets are very small! like this text!
Tap this link (here…) to learn how to remove the carbs off the bike
Can I do this on a stock 125cc un-modded bike (ie. brand new machine)
Not really, it is already running leaner, so raising the needle may help a bit but jetting and uprating the electrics a little will make this mod more effective , because raising the needle makes the mid range a bit richer. (extra fueling)

FI light on! GV250

HELP!

The FI light on my GV250 Comes on as usual with the ignition, but stays on even when the engine is running.

The EFi manual talks about a “Flash Code” but the lamp is just “On” no flashing!

Is there an on board diagnosis socket anywhere?

Any ideas how to reset the ECU?

Any help or suggestions welcome.

David.

GV250 Can chain adjustment.

Hi, Can anyone tell me how to check/adjust the cam chains on my 2011 gv250 please?

Thanks

Wellsie

How to change Vacuum Lines on Hyosung GT125R GT250R & GT Comet (Air Hose Diagram)

Changing the vacuum Lines on carburetor 125/250 vTwins, should be fairly easy. All you need is 15-30 mins of your time, let’s start with the basics first.

Hyosung says if your “standard” factory lines are 2-4yrs old. Discard them regardless.
Old pipes can also rot inside , especially those chinese ones with trashy rubber
Larger colder air pipes can help improve the vacuum system but get strong clips!
Strong clips are very essential to avoid all possible air leaks.
This tutorial applies to all carb operated 125/250 GT & GTR Twins (includes GV125 too)

Let’s go now… Strip your fairings down (GTR owners)
(if you have a naked bike, go to next step)
hyosung gt125r air vacuum line gt250 gv125

Below is a diagram of how the “AIR LINE” system should be connected.
Study (look at) the diagram images below first , before moving on to the next step….
//
//
hyosung gt125r air vacuum line gt250 gv125

VACUUM LINE #1 = CONNECT THE REAR FUEL PUMP FIRST
Got your lines ready?
On the LEFT side of your bike Grab a hose for the fuel pump & follow the next diagram pictures below:

hyosung gt125r air vacuum line gt250 gv125

VACUUM LINE #2 = CONNECT YOUR FUEL TANK TAP
* Once your rear fuel pump is connect from the left side.
* Now, move on the the RIGHT SIDE of your bike
* Grab a second vacuum pipe and follow the next diagram images below:

hyosung gt125r air vacuum line gt250 gv125

That’s It – Vacuum Setup is done! 🚦
However, if you have an AIS Device (Fake emissions/EGR) then read below!

*Remember above ^ , there is a cartoon diagram of the infamous “EGR DELETE” mod, right ?
*Remove it or block anything that feeds it.
*This image is another example for you.
* Personally, it’s a useless device.
* But, if you want it connected -> replace “blocked” with “connected”
//

Alright, we are done. Go test ride! 🏁

I hope this fast toturial was easy to follow, however if you get stuck or need help. Just comment on this post! This tutorial should also help GV owners since they use the same rear pump anyway.

[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250

Hyosung Carb 250 125 GT GV Pilot Jets Main Jet

How to swap Carb Main Jets on Hyosung 125/250cc v-Twins

Carb Main Jets one of the most common upgrades to do on these 125/250 carby twins. This tutorial will show you how to swap carb main jets the easy way. #SwapNGo!

First things 1st, if your bike has warranty, consult your dealer before attempting this. This may void warranty on new bikes.

Anyway, Let’s cut to the chase!

0. The tools required:
– Large Mole Grips (& a small one too)
– Philips (+) Star screwdriver – Regular Length
– Philips (+) Star screwdriver – STUBBY LENGTH (Shortie)
– A small amount of cooking oil
– Hex Bits (& screwdriver Bit) (if you have stainless bolts on the carbs)
– 10 or 12mm Spanner or Socket Tool.
– Flat-Head ( – ) screwdriver

1. Whenever you’re ready, unscrew the bolts that hold the side-panels of your bike. Then take off your fairings!

Owners of Naked Bikes = Skip to #2. (GT Comet)

Tip for GTR Owners = Place a rug under the bike, and when your fairings drop to the floor as “ONE piece”. Carefully push one side under the bike, so the whole “one piece” can come out safely off the bike. One Piece means “left/Right Side Panels & Middle Engine fairing attached as one.”

2. Get the tank off the bike next…
* Unscrew #10 (fuel tank bolt) pictured below & lift up the tank “slightly up” so you can see the fuel pipes.
* Disconnect the fuel pipe safely from under your tank (marked in red circle!)
* Don’t forget to also disconnect the “small” vacuum-air hose that is also attached to the tap
(Some GT Naked bikes use a manual tap on/off Tap instead of a vacuum fed tap)
* When the pipes are off, remove the whole tank away from the frame.
(Watch out for item #3 – These rubber things fall out sometimes)
(Save Picture to device to view it much larger)
hyoriders

3. Loosen the airbox clamps
On the LEFT side of your bike, directly under the airbox. Grab a stubby/shorty (+) screwdriver and unscrew loose the 2x clamps on each side of the carb.
They are marked in the red arrow as reference. They are black in colour.
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

4. Remove the airbox away from the bike.
Take your airbox off & put it aside for now. Jump to #5 next.
* Don’t forget to remove the 2 bolts holding the airbox to the frame!
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

5. Your bike should now be exposed like this…
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

6. Next up, let’s loosen the rubber intake clamps…
On the red arrows pointed -> unscrew loose the clamps holding the carburetors down.
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

7. Lift up your carbs out of the intake boots (just a little!)
Yes leave everything still connected (cables & pipes)
We still have to drain the fuel out , so jump to #8
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

8. Get a bowl & do this on a VENTILATED area or outdoors! (Fuel Vapor)
* On the red arrows , unscrew these 2 bolts about half-way out.
* Fuel will start dripping down the small pipes under the bolts
(fuel is draining out)
* Grab a bowl or bucket and capture the fuel (watch for spillls!)
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

9. When the fuel is drained completely…
UnHook the idle-screw adjuster.
* On the left side of your engine, there is a black “hand” screw that controls idle speed.
* Unscrew the STEEL bolt that holds it down (Look at red circle picture)

GT Comet Owners = Skip to #10.
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

10. Phew…. Let’s remove the float bowls now!
You can do this SIDEWAYS or FLIP the carbs over a bit, as pictured below…
Remove the 8 screws that hold the float bowls down.
* Be warned! = Some original screws can be harder to unscrew loose. So be ready to use some force!
* To be honest, Mikuni should really start using stainless bolts anyway!

11. Struggling? Grab a pair of mole grips!
* When a screw is being difficult to remove with a screwdriver.
* Adjust your mole grips to bite a small bolt head
* Make sure it’s strong enough , so it’s doesn’t slip!
* Bite the bolt head –> Turn left. It should squeek loose.
* When the “bolt” is loose, use your original screwdriver to remove the bolt entirely.
* * * It’s common for these carbs sometimes to have rusty looking screws. * * *
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

12. Finally, we get to the real thing. Your carb’s undersides should be exposed now!
* Next up , get your “Upgraded” Jets ready!
* Take a 5 min break!
* You are going to swap your standard carb main jets jets for the bigger ones.
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

Information On Carb Main Jets
Depending on which model 125/250 v-twin , it is important to remember these points:
* Stock GT125 / GT125R & RC = 87.5 Front Main Jet & 90.0 Rear Main Jet
* Stock GT250 / GT250R = 92.5 Front Main Jet & 95 Rear Main Jet
* Stock GV125 Aquila = 87.5 Front Main Jet & 87.5 Rear Main Jet
* Stock GV250 Aquila = 90.0 Front Main Jet & 87.5 Rear Main Jet

All 125 vTwins = Size 15 Pilot Jets (Front & Rear) = Don’t change it.
All 250 vTwins = Size 20 Pilot Jets (Front & Rear) = Don’t change it.

If you change exhaust pipes to “free-flowing” (aka. stainless pipes/straight through) = Then it is even more necessary to upJet the v -twin carb main jets.
If you have an aftermarket Air Filter such as “K&N” = You also need to upJet
(more air = more fuel!)

13. Ready? Let’s upgrade!
Swap the front & rear carb main jets for one size up each.
GT125/GT125R = Upgrade to 90 FRONT & 92.5 REAR
GT250/GT250R = Upgrade to 95 FRONT & 97.5 REAR
or
GT250/250R = 95 & 95 ( For Aquila 125/250 = One Size Up each. )
* Okay, see the red circles ?
* Unscrew each jet & replace them with a bigger one.
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

14. Double check that the jets are secure & tight before closing up!
* Take note! – These jets are brass, so don’t over-tighten them!
* Make sure your carb is also clean from any visible dirt or dust particles.
* The Jet Holes are very tiny! …(So a clean area is a must)
* A Carb Cleaner helps clean up old carb parts & carb main jets !
[Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Jets

15. Grab some cooking oil (or old motor oil)
* Drop a “SMALL AMOUNT” of oil on your FINGERS
* Use your fingers to SLIDE OVER the black gaskets…
* Keep doing this until both gaskets have a nice coat of oil-film over them.
[Tutorial] Carb Main Jets Hyosung GT & GT 125/250 - How to swap carburetor Jets

16. All done? Time to close everything up,
^ let’s do things in reverse now ^ #12 -> #1…
Start from #12 going back to #1 – Always double check each step you take!
Fit all your parts back together.

17. In the end , this should be the final outcome
[Tutorial] Carb Main Jets Hyosung GT & GT 125/250 - How to swap carburetor Jets

18. Install the Fuel-Tank (& also connect pipes!)
* Also, check that all screws are nice & secured such as: 2x Intake Rubber Clamps, 2x Airbox Clamps, Carb-Float Bowl Screws & 2x Carb-Fuel Drain screw closed up too.
* Inspect your throttle cable (Twist your throttle grip to test!)
* Ensure your Choke Line is working (Test your choke = The carb will slide its choke rail!)
* Check your fuel drain cable is AWAY from the engine (zip tie to frame & let it point to ground)
* Lastly, make sure the “ENGINE IDLE” HAND-SCREW is also attached properly
[Tutorial] Carb Main Jets Hyosung GT & GT 125/250 - How to swap carburetor Jets

19. You should now be ready to start!
This quick ten second video was taken, while the bike was still cold & we swapped carb jets.
This 125RC was only 600 miles old, no choke was used.
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20. Trouble starting?
* If it doesn’t start the first time around. That means the fuel inside the carbs hasn’t reached “capacity” yet.
* Put the CHOKE lever on max setting (towards YOU)
* Then Crank the bike for about 5-7 seconds (while TWISTING the throttle a few times).
* Then it should fire in to life. Let it idle for few mins to burn off any excess fuel that could have made the spark plugs wet.

Still got some trouble? Get a can of Bradex EASY START – Spray lots of it inside your air filter hole. Now crank the bike again & it should fire this time round!

Factory Troubleshooting Guide for starting issues.
(Save the images to your Device to view it much larger)
[Tutorial] Carb Main Jets Hyosung GT & GT 125/250 - How to swap carburetor Jets [Tutorial] Hyosung GT & GT 125/250 - How to swap carburetor Carb Main Jets

21. The end!🏁

You should be miles away in to the countryside or your other scenic spot!

I hope this tutorial was easy for you to follow. As always, if you have any questions or feedback, just reply below!

– M

[Tutorial] Hyosung GV/GT 125 & 250 Clutch Plates Replacement How To

Learn how to change Hyosung GV/GT 125 & 250 Clutch Plates on the GV125 / 250 Engines (GT/GV)

💥 NOTE! – SOAK YOUR CLUTCH PLATES IN OIL FOR 24HRS BEFORE DOING THIS! 💥

🛠 Tools needed ::

Size 8-10 “O-Spanner”	Stubby Flat Screwdriver	Allen Keys (if needed)
Oil DrainPan	Size 15/17/19 Sockets	Pliers or MoleGrips
Rags	Time	Patience

Optional 19mm socket/spanner for CNC Magnetic Oil Filler Cap

🎁Parts Replaced ::

Clutch Plates (fibre)	Clutch Bearing	Steel Clutch Discs
Oil (1.5L) JASO MA2 Grade	Oil Filter & O-Rings

💪Skill Level = Anyone can do it, but if unsure, speak to a mechanic. (Take this guide with your risk)

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

⚠ Symptoms / Troubleshooting Hints …
Always replace your clutch plates when you notice the following:

every 5000 – 6000 miles. Regardless. (just like “brake pads” have a wear limit!)
when you see your self adjusting clutch line frequently.
when gears feel notchy / hard.
when bike slips up during gear changes.
Does your “Clutch” basket have any “knocking” feel during idle ?
Does your bike “rumble” when you hold the clutch lever in?
not as fast as before (acceleration wise)
Clutch seems to “slip” on hard acceleration

🔧 Let’s fix it….

Technical Inspection (What to look for inside…)

Clutch Plate Thickness Limit = 2.6mm (New ones range from 3-4mm)
Clutch Spring Free Length Limit = 36.2mm (Normal range is 3.8 to 4.6mm)
See any deep grooves on the Clutch Basket?
Time to replace it entirely! – This applies to some bikes after 13-20K miles of their life regardless.
or if the damage is very minimal, gently file it until it’s smooth.
Silver Clutch Metal Discs (separators) – 1mm distortion limit.
Loud Rattling Sounds on the clutch cover?
(your clutch plates *may* have cracked in pieces)
(Must replace them ASAP as these things can block oil passages inside or worse!)
Clutch basket center nut must remail tight with its washer intact.

🚦 Let’s begin!!!

Park your bike , get your tools out. Start with the drain pan…. Drain Oil 1st…

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Get either “15mm / 17mm / 19mm” Socket , go under the bike and drain the oil.
A. Clean the Oil Drain Plug
B. Once the oil is 100% drained.
C. Fit the plug back inside.
D. Tighten to a maximum of “15 Foot Pounds” (or 20 N.M) (Torque Wrench Value)
If you don’t have a “Torque” wrench. Then just tighten your nut UNTIL you yourself know when it feels tight enough!

🔥 BE WARNED! – THIS IS THE “DRAIN” PLUG
(DO NOT UNDO ANYTHING ELSE UNDER)

Ready? Get the NEW clutch plates & discs out…

In the blue circles^, remove the engine cover bolts.
Remember where each bolt goes! – Some of them vary in size.
🔥 Be warned, left over oil will spill out!

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_

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

When you reach the oil filter – Be warned, that the rod goes all the way in to the engine.
So the quickest way to remove the rod safely is to:
1. Put 2 nuts on top of each other.
2. Undo the 2nd nut…. (the TOP #1 nut is a “stopper”)
3. Undo the 2nd nut until the rod comes out entirely.
🔥 NOTE – in some cases , a pair of mole grips can undo the stud with some force – but it may scratch the bar!
_
_

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB
Don’t Lose the O-Rings for the filter cover!
(there is 1 for the cap & 1 INSIDE the oil filter hole. = 2x rings.) (Ps. Its not blood^ but red oil! 😉 )
⚠It is always recommended to replace o-rings & filter “whenever” there is an oil change job or clutch changes.

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Once all the engine clutch cover bolts are removed….
Use a stubby tool like a small screw driver…
1. Go under the bike and tap slightly the “marker” in the blue circle (^LEFT PICTURE)
2. Once the cover splits – Go to the TOP of the clutch cover.
3. Near the oil cooler pipes, put the screwdriver or a blunt knife to twitch the cover (towards you)
4. Now, we have some movement…
5. Remove the clutch cover!

. HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB
🔥 NOTE! = The “gasket” must be removed and replaced with a new one
(Sometimes old gaskets may tear off!)

.
.

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Now your clutch system is exposed.
Get size 8 O-Spanner & take the bolts out…
From top down….
Undo => Top Bolt 25% out => Bottom Left 25% => Bottom Right 25%
We now have 3 bolts undone slightly => now undo the rest 100% (take em out)
Then remove the last 3 bolts – This method protects the clutch springs.

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Remove: front clutch hub facia plate cover and investigate the parts below (just inspect them)

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Take out your plates one-by-one … this is very important…
Remember the ORDER of each plate
‼Hint: The last plate is always “Fibre” & the FIRST plate is always “Fibre”
‼Hint: STEEL DISCS (Seperators) go in between.
Done?
⚠ Use the SAME ORDER to fit your new plates! Or use the diagram below…

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

Then fit back the other parts in the diagram above^
These numbers are the parts in diagram above^ #13 => 17 => 16 => 9 => 10
This is the ORDER of fitting them….

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB

It’s time to tighten it!
Remember start from the TOP 25% screwed in => then bottom left & right 25% each respectively => Then maximum (100%) on the remaining 2 => The first x3 bolts , 100% also.

This method is to apply equal pressure everywhere to protect the clutch springs. Hyosung books also mention the criss-cross star style of fastening bolts.

🔥NOTE = A CLUTCH BOLT IS HIGHLY SENSITIVE TO OVER TIGHTENING.
ALL CLUTCH BOLTS => MAX TORQUE 5 FT LBS (FINGER TIGHT!)
A torque wrench really helps!
or else Tighten with 2 fingers (and that’s tight enough)

HYOSUNG GV 125 250 CLUTCH PLATES uk hysoung FORUM OWNERS CLUB
Last not, least – Close the clutch cover. Top up your bike with oil.
Remember these points below…

MAX Torque for “clutch engine cover boltd” – 5.5 ft.lbs
(It’s made of aluminium)

Required Oil = 2x 1L Bottles
(Fill up 1.6L of oil)
Tap this blue link here for a tutorial of oil change

Use fresh Oil, O-Rings , Filter & Gasket.

Record this event in a book somewhere or back of owners manual – This creates a log of your work & record mileage

👍 Recommendation = Make sure your oil is marked 10w40/10w50 JASO MA2 ESTER – Nothing upsets these v twins than running junk overhyped (yes, over-hyped) castrol oil , (Many small parts in a hot small v twin!)- That tells you all you need to know – Good oil is a MUST. Motul & Silkolene are best.

🏍 Ride Safe! Any questions hit the comments below!