♠️ M77
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I’ve considered doing this myself and as I need new sprocks and chain I’ll have to go for it me thinks
Go for it!
Send me an email of your riding style please and what kind of roads you use so i can customize the gearing if need be , otherwise i will send the kit as optimal as i can be for both accel and top end (balanced but better than stock 😉 )Hi Marcel, Thank you for your comprehensive reply. I have posted a photo of the fuel tap that I need as requested. From your suggestions I have a plan and a list of things that I need to check and to buy. I will start with the more essential fuel related parts and then review. I have some questions: 1.The manual says not to touch the mixture CO screw so does this definitely have to be left alone? 2. How do you remove the pilot jet? 3.How many turns is recommended for the pilot screw? Thank you again and I now feel that I have a more methodical approach following your advice
- & 2 = We will get to the mixture screws and adjustments when the bike feels like it needs to or when you replace the mixture screws (with orings)
Korea generally discourages it as they have done it spot on from the factory, some GV Aquilas use the same engine and carbs as the GT , but they tune it different sometimes but not “that much” , as to keep things uniform with 2 cylinders in harmony with each other They also make the rear slightly richer as it’s the hottest (due to less air flow going to it)Either way i will advise accordingly , privately , i’ve known someone to copy my mixtures and didn’t turn out very well on their bikes because i have modified the bike differently to theirs & different parts on different bikes etc . General rule of thumb is that beyond 3 full turns out has no effect on most bikes with a CV carb like yours .
3. A screwdriver that’s flat will slot in the pilot jet. And turn it left gently, it should just unscrew out pretty easy , unless dirty , allow the carb to be soaked in carb cleaner for sometime to agititate the dirt.
You can remove the tap, and soak it in carb cleaner to ensure all debris is gone.
Also you can unscrew the dirt trap that’s under the tap (it’s a cap than needs a socket/spanner to unscrew it off)Then it is pretty much ready to go. You may not need to replace it unless there is a leaking concern with it (ie. orings)
Carb, probably the first part we can address, so here’s some pointers to check for:
- Float height is indeed 7mm when the carb is upside down on the carb , that is the float resting on the fuel valves.
- Lift the float gently, and see if it bounces a little? – If it doesnt, consider the fuel valves to be replaced under it.
- Pilot Jets should come out as they are soft brass and the carb body is just as soft too.
- ultrasonic cleaning really does pay dividents or air compressor session on every hole thats inside the carb.
- This topic is also a good read in regards to jet sizing, ensure the Pilots are both size 15 each. The factory mains are 87.5 front and 90 rear , upgrade size is 90 and 92.5 optimally
https://hyoriders.club/forums/topic/tutorial-hyosung-gv-gt-125-250-how-to-swap-carburetor-main-jets/#post-5592 - Check the slides for wear, and check this topic out below to see if the needles are on “middle setting” or “rich setting” – you don’t want it on the LEAN setting
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
it should be noted slide needs from the shop are upgrade ones that allow more fine tuning (5 or 6 grooves) – They always come as a pair for good reason.
https://hyoriders.club/shop/service-maintenance/jet-needle-carb-diaphragm-hyosung/ - lastly when the floats come out, the fuel valve assemly has a mesh under it, it can get clogged with some debris , becareful taking it out as its soft brass
But you will get new ones anyway , should you end up getting yourself a rebuild kit as precautionary. Who knows how old the gaskets are at this rate.
Fuel.
E5 only. Hyosungs don’t really E10 , even modern cars in general due to the fact:
– Extra ethanol doesn’t stay fresh for that long, and can be corrosive towards rubber parts (any thing rubber related including intake manifold pipes) , and can be corrossive towards steel parts (tank etc) , and makes carb cleaning annoying after a while of sitting.
Air Box fitting to avoid leaks
- Make sure carb is empty first
- Put the carbs on to the air box
- tighten the clamps on the airbox hard. but not too much.
Now then,
- Hold the airbox and carb together, and carefully drop the whole thing in to the bike until you feel the manifolds swallow the carbs secure.
- Please… manifolds are very hard to source now, as Korea stopped making them, so try your best not to stress them or cause them to split. It can be a costly thing to get a new one!
- make sure the carb clamps are NOT catching linkages of the throttle of carb
- test the choke is working
- test the throttle cable is moving freely
- check your carb to make sure nothing is catching the metal clamps when the throttle is twisted on and off.
- and ofcourse, secure the fuel line tight , it may get awkward trying to do it with the airbox already there
or Fit the fuel line on to the carb before carb goes on the airbox, then the fuel line other end will just join the rear pump when you are ready.
This is the best way to guarantee there is no air leaks.
Speaking of air leaks, see below
Intake Orings.
I can’t stress it. Be very patient if you see an old bolt thats on the manifold rubbers and measure their length. Run to halfords and replace with Stainless steel with a washer.Now then, make sure the surface of the engine is very clean where manifolds sit on, and do your best NOT to allow dirt to go inside as valves may get scratched up or cylinder walls of pistons when debris is floating around inside. So mask the holes!
Don’t sand anything off, just use a plastic scrapper for stubborn dirt.Make sure the metal surface area of the intake pipe is sanded off (use fine or extra fine sand paper)
Get racing white grease (high temp motorbike grease) such as Putoline i use.
Get new orings below (they come as a pair)
Intake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
Now, everything might be perfect ? But if orings are old or fishy ,it will cause half the issues you have described above too.
Often overlooked, but just as crucial as you sealing the airbox too!
Mixture Screws = This will be address as a last resort when we are sure we have diagnosed every part of the bike first. But please, they are literally the most easily rounded off , ensure the area there is soaked with carb cleaner and flush out the dirt before attempting to turn them.
Mixture screws do have orings too, (for a reason) under the spring so nothing leaks fuel or air otherwise and can make fine tuning annoying, new screws already come with the orings anyway as you saw at the shop.
But make sure the mixture screws HIDE under the black bungs when done or see this product here for clarification
Make sure the screw driver is “exactly” fitting, or it rounds off easy. Could be a day job trying to extract the old screw out!
Have i helped so far ? Let us know how you get on!
Plus, i did not see the picture of your fuel tap, so please upload on this forum if you can – Click the “Add Media” button above reply box you write in.
Hello,
If your LEFT FORK at the bottom has a digital sensor attached to the wheel spindle,
Take it off;- Inspect the wires for water including plug end that connects to the dash harness.
- Add some thick grease on the actual speedo drive unit, the factory grease tends to wash away in rain.
- Test run and see if that helps
- Your dash will have a “digital” LCD display bang in the middle of RPM & MPH counters . The LCD unit counts the fuel level digital
This is for GV’s that are of a later model (which i assume you have)
If the left fork has a MECHANICAL speedo driver which a cable that hooks “directly” under the MPH counter of the dash (not electric)
- Take the cable off and inspect it. The cable is more likely to fail than the actual manual speedo drive unit
- As before with the digital comments above, inspect the mechanical unit and grease it well.
- Your dash will have a “Manual Fuel Level Gauge” for older GV with mechanical speedo drive as a hint.
Lets see if that helps ?
In regards to the TALE TELLE lights above the LCD Screen…]
Full Beam = Powered directly via switch gears
Indicators = Harness & Switch gear signals sent to dash.
Neutral = Your new incoming sensor should bring the green N light back onAlso the dash has its own mini harness trunk that deals with lights too. Have you checked the mini harness ?
It may sound silly to ask, but i hope you have been using E5 fuel havent you?
E10 fuel in this country is doing no one any favours even the most efficient injected cars / bikes do better on E5.Also , if the filter is very clean (zero particles) , the tank isn’t rusty (phewww)
Go to halfords and buy WYNNS GOLD PETROL CLEANER. Pour the whole bottle per 2/4 full tank. Ride until the bike is low.
Let us know if the “soft-clean” did the trick , if not , then i’d advise the carbs to have a good blast from the air compressor everywhere inside it with carb cleaner from WYNNS too. Or your local carb ultrasonic man can do this for you.
Can’t hurt to make sure the carb unit of the bike is totally checked over, cleaned and out of the way.
Then if the bike still misbehaves, we can dive in to other areas since carb is fully rulled out.
Also try what the guy above me has suggested too ^ .
You’re more than welcome. Ride easy this winter and enjoy the bike 🙂
That’s great news.
Can you show us when you get a chance what the center of the spark plugs look like ?
K&N doesn’t exist for the GV125, however, the panel filter & airbox flows enough air to power a 250cc. I wouldn’t worry too much here. The GV250 carby uses the same airbox. GV250 EFi Injected & Carby use the same air filter as the 125GV Carby.
Lets see the analysis of your plugs i’ll determine what’s going on in the piston chambers.
Hey,
Now i understand…. I’ll try to break this down.
TOP BAR FITTING:
1. Remove the clip ons , they are for a GTR ofcourse. Keep them as backup
2. Since the top steering yoke plate is off (aka. Top Tree Clamp)
3. You will see 4 spots which Korea generously put there.
4. Drill through them.
5. You can now fit the bar risers + straight bar + long bolts and nuts x4That’s the steering done.
SWITCH GEARS
The GTR ones are shorter, so caution that.
You may also have to drill the STRAIGHT BAR some holes for the switch gears to fix themselves in to , so they don’t spin. Same spots as the clip on bars. You will see as you disassemble the bike.You may “50/50” be able to get away without messing with the harness or changing switch gears.
CLUTCH , CHOKE, THROTTLE & BRAKE CABLES
If this bike was a GTR, you “must” change the cables above ^ in the bold title for a GT NAKED version because GTR lines are only short enough for the low clipons.
Get a KOREA 7.6inch headlight off a GT650 Carby or GT250 Carby
The classic round shape. (I haven’t got one, it got sold)do NOT get GV125, GT125, GV250 ones. They mount different.
and these 3 bikes use SLIM upright forks too. It’s messy.If you want to use your aftermarket ones, be ready to use spacers.
See below….
Headlight sorted? Get this item below:
https://www.ebay.co.uk/itm/255073173921?hash=item3b638bc1a1:g:24MAAOSwZNRhBaNK
Proper Dash Mount…. Get this item below (digital dash only)
https://www.ebay.co.uk/itm/255073179908?fits=UKM_Make%3AHyosung%7CUKM_Model%3AGT&hash=item3b638bd904:g:2w0AAOSwqGxhBZr7
Front End Styling, get this item below
https://www.ebay.co.uk/itm/255058268696?fits=UKM_Make%3AHyosung&hash=item3b62a85218:g:EIIAAOSwc01g8dEU
Now you have a proper GT Naked bike that’s OEM looking as Korea intended.
Hope this helps!
The ebay links are from my shop.
Have you looked at this topic below ?
Which shows how to add a nose cone from the GTR to a Naked Bike that doesn’t have 2 factory holes at the head stock (where VIN is engraved)
Can you attach pictures of the bike to see if Korea mounted the factory holes for the GTR Front Nose cone mount (under the ignition barrel where VIN is engraved)
Also helps us to see the situation you have…
What colour is the plug sparking on each coil ?
How are the coils ?
How does the plug look (if you can attach pictures ?)
Also watch for the temperamental HT caps (common)Henceforward, we tend to change the whole ignition sparking system parts to better items.
Keep us updated, as i have eyes on this topic and have responded to your email , i do hope the main harness is salvageable to be saved and like simon says go ocd with it or least go crazy with the tape and also ACF50 is a good friend to prevent weather turning gold terminals of (any) connector in to yucky green which signals or electrical juice won’t pass through efficiently (oxidization of terminals does happen) , winter sucks (hence we do things to make their life easy and we don’t fancy having to take something apart every week in the ice cold!) but summer is great.
Hey welcome to the forum club 🙂
Post some pictures of your ride as some journal topic , we’d like to see how you get on with it considering there is a lesser amount of 650s in the UK than smaller CC Hyosungs actively on the road. So keeping this one on the road is music to us all.
Let us know what you have discovered from it , any history , any changes (like some part that’s been changed from the stock setup etc)
We could end up narrowing down the “to do list ” / “to look out for” list as you wanted to know , and sooner you finish your project the sooner you can go about with it.
If there was any ideas of putting more 650 parts on this shop , let me know and i’ll do my best , it’s not hard for me to query & get stock parts in trade but wherever possible i tend to replace & stock things with better ones . What’s on the shop will also give you an idea what direction I am going for , and what people commonly replace. It may be smaller CC bike parts occupying most of the shop catalogue but principal can be applied to the 650 although they tend to live well untouched as long it’s definitely taken care of & serviced accordingly as per service intervals. Just the smaller CC bikes have a harder life that’s all .
What a nightmare, no wonder you are talking about cliffs. Must have driven you nuts. Well done for sticking with it and not torching the bike. What advice did Marcel give that eventually fixed it?
I sent him a new pickup coil as everything else checked out to be inspec as per service oem limit. Hence we got busy with the meters.
What happens when you unplug the stator and regulator from the bike then add a fuse back on ?
If the bike turns on the dash without the stator or reg connected, you found the issue (although it’s rare in UK , but dead blown regs actually blow fuses if the rider tries to turn the bike on)
However nothing great about Korea’s charging system even 650cc, so hence we change that to slightly better or go all custom (varies on different models and cc’s )
If unplugging the reg and stator made no differece, let us know
Hi Guys, is this on the new 2021 bikes, I hope to god it’s not, as its getting sent straight back to Korea2 or 5 Year warranty (dependent on Sinnis UK and your dealer & if Hyosung still wants to Honor 5yrs , but i think so.) , and i wouldn’t worry too much as the injected engine is entirely different , so any issues your dealer will sort it for you under warranty , just take care of her and she will keep going.
- & 2 = We will get to the mixture screws and adjustments when the bike feels like it needs to or when you replace the mixture screws (with orings)
