♠️ M77
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All factory bikes i’ve worked on = 92.5 front , 95 rear on the 250cc models.
I wrote 95 front and 97.5 as upgrade jets because people start using freeflow pipes like black widow stainless and use proper afternarket cans such as Lextek OP1 , Black widow cans , MTC cans (not the crappy stubbies from china) and they put K&N air filters (not cones!) – never use cones.
This is to stop the bike leaning out on full throttlePilot Jets are size 20 front and rear, forever. (this size is more than sufficient for a 400cc even), so no need to upgrade.
The nut that snapped is called HOLLOW BRASS ACORN NUT , you will find it at the shop (purple button right at the top of the site black bar), it is very fragile! 👀
if the carb is that dirty , i implore you to change the INTAKE ORINGS that sit under the rubber sockets going the cylinders (inlet manifolds) , same rings are at the shop , use stainless bolts everywhere possible!!!
Other carbs = big money to a wizard to make airbox and new manifolds , cables , then carb tuning etc to make hyosung engine happy to run it.
Mikuni being japanese is a good carb if the last owners did not piss them off, so i can understand your frustrations.
you have to explain in a lot of detail what it is doing ?
how does it start?
how does it idle?
is it worse when hot ?
what rpm is best for her ?
which rpms does it bog down bad?
have you replaced the pump ?
are fuel lines and vacuum lines kinked?
is the tap on the tank replaced or did you clean it ? (it has dirt trap at bottom too like a big square nut)
what size pilot jets?
what size mains?
go to mixture screws , replaced them? the rubber orings may have gone bad and is leaking out
did mixture screws got touched ? how many full turns out are they ?
as cobra says = float height is key
Glad you got that resolved 😉 , yes Hyosung uses the same tube for GTR bikes that have shorter cables , and your naked GT is longer, so it helps to adjust to suit your comfort. who knows if the previous owner did things the wrong way!
Welcome to both you and the young mechanic in your garage!
tutorial for egr block off is in tutorials section even for the 650cc is the same principal
tank – how will you know you have low fuel ? the bike behaves worse when fuel level is too low in tank (as quoted from service book)
the vacuum taps are okay , they work nicely with vacuum pump – i tried bypassing, the bikes hate it. so respect to korea for leaving the pump on the frame for high speed runs
so far we are okay, just be patient extracting the exhaust off lol.
ever tried a yamaha local dealer for the jets? cant just use random jets as the carb has soft threads. easy to damage them.
the service manual should have a page that talks about what oils and anti freeze to use in engine and how many litres
cute seeing mini damsel going over dad’s ride before he sets off lol. get that ‘all clear’ from her first! 😉
Due to the nature of our 3 phase stators and our regulators , the Hyosungs flactuate between 13.5 to 15V max as the accepted service manual standard , so in thus , they advise to use AGM batteries (maintenance free type)
The best brand is YUASA , with UniBatt & VARTA (German) coming a close 2nd tier. Everyone else is overhyped junk. I’ve always trusted YUASA ones from Halfords and Bike shops (rather than getting it online due to risk of fakes or outdated old stock) – If buying online, make sure the seller verifies the battery isn’t older than 2 months max even if he says its fine (he wants money) , batteries are not things i want to play with lol.
Lithium relies on a constant steady supply of 14v (not more than 0.1 v above 14.00, not even o.2v less) and if something goes badly wrong, they are very explosive!
Get a JIS screwdriver as it is not normal philips. So a JIS driver is easier.
Then remove only the float bowls and top covers. Leave the rails attached to keep the 2 carbs joined. Gain access to an ultrasonic cleaner. There is a lot of videos on youtube if you type in “how to clean CV carb” as our carb is a CV type.
Red pin is idle adjuster. Looks aftermarket as old owner likely snapped old one.
Cables that go to the carb are CHOKE on the rail and also THROTTLE cable at the side of the carb.
If not access to Ultrasonic cleaner or lend the carb to someone in garage who can do it. It is possible to use 10x cans of carb cleaner at halfords (yes you will go through that much believe me)
Will edit original title when i get back for sure. Whatever you do. Take your time. Believe me you will keep your hair that way!
Edit, i was typing a long reply , and my stupid PC deleted it! and it’s almost 9pm , long day lol – Frustrating lol. So here is the short version
Email us below with a specific list of what you need , if i don’t have it on ebay (where you found us) or on this Hyoriders Shop, then ofcourse i will buy a new one for you
If you can’t be sure what the part is called , i will respond back asking for a picture you can edit with a circle or point your finger showing me what it is.
I was also going to say i am glad you’re saving her and this thread could be renamed/edited to have a new title saying “Saving GT125R from Hades, Rising a phoenix!”
I will follow this topic as It would be interesting to see how you get along with it 🙂 , don’t scrap anything that can be future handy spares!
Yes it is needed to stay there because both cylinders actually move fuel back and forth , and sometimes it is to help escape some air pressure on to the road if it builds up in the float bowls.
Shorting peharps ?
Ie, a naked wire touched the frame somewhere near the steering head , or along the left side of the frame towards the back or back seat has water in the wires going to tail lights ?So its a full strip down to investigate the harness (ONLY if you have tried my previous comment above first)
Try my previous comment above where i talked about plugs to check , sometimes maybe the ignition wires broke off under the oil cooler resulting no power to the bike.
I hope it’s that , instead of a bad regulator frying the electronics for good.
Speaking of parts = Send us an email for personalized sales quotes , otherwise , have a look around the shop and email us if you want something else we didn’t list up.
I realize this topic is old from 2020 , so whatever you do, reply on a brand new topic of your own if you can ,
Nice Job! – Edited the title so its easy to find for anyone else too.
The GT250 Naked uses 1/2 or 3/4 piston due to it having a single disc.
The GT250R uses a 650R master cylinder that has a 5/8 piston to be able to brake 2 discs.
So if you want to use 2 discs , get the 250R cylinder (which borrows from the 650R anyways)
Yes 1 & 2 join together = then it becomes overflow to the road surface. If the bike falls on its side, or accident , the carb should dump its fuel right out of those pipes 1 & 2
#3 = Yes join both bowls there , the accelerator pump actually sends fuel to both bowls , to squirt fuel towards the cylinders.
No problem,
I recommend Motul 7100 Ester Grade oil , it is best oil for Hyosungs and the second alternative i trust is Silkolene Pro 4 Ester Grade oil
You can check out the other info in the service book (click this link here)
Hope this helps
Go on the carb , remove it and see if there is a “throttle plate” attached to stop bike going full throttle (some EU countries have restrictions until rider upgrades license)
Or take it to a DYNO shop , and tell us the real power made, the guy will also look around for any restrictions added by previous owner to limit its power. Usually its the throttle , carbs , and exhaust and intake restricted.
It’s not possible to restrict Korea’s CDI’s.
If it is EFi , yes it is possible to fine tune it but it has to be DELPHI ECU only. Older ECU’s on EFI bikes are too difficult.
On the plus side, with Kawa bars you can fit custom bar ends!
