Ucvmn
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I already did that, but with a 250 EFI engine. I used 125 carbs, but I replaced the main and pilot jets. I had to replace the rotor and the stator in order to make the ignition system work. Now the bike runs, but I have some problems. I suspect it’s fuel starvation… I’m figuring it out.
Check your float height , after every ride on my carb bike = the big filter is usually full. Or your float needles are jamming causing some internal engine slow leak of fuel in to cylinders = Your manifolds will be “wet” inside as a hint. Also open “OIL FILLER CAP” ( on the clutch cover) and sniff inside hard. ==> If you smell fuel => change oil before riding again. Can you also clean your spark plugs , go for a short ride => wait to cool down => Take pictures of spark plugs so we can see the mixture ? Simon also has the EFi 250 motor, he knows if the fuel system is too rich or too lean,. Pictures of spark plugs will help OR It could be electrical! (Coils? Stator unit?) (Since stator is also part of ignition system = high revs , more pulses to cdi , cdi talks to coils to spark the plugs. , dashboard tells you how much RPM engine is doing
Okay, I’ve never checked the float height. One question, should I change the needle jets on the carburetors? Because in the manual, I see that for the 250 and 125 they are different. The spark plugs now are new CR8E, I’ve ridden 150 km today, I’ll take them out and upload a photo. This might take a bit because I’m a bit busy this week.
If the float needles aren’t working, the fuel filter should lower the level when the bike is off, right? It doesn’t. Last week, I removed the airbox and the carburetors to change the spark plugs, and the intake manifolds weren’t wet with gasoline. The fuel filter only empties if I accelerate to the maximum.
Do you then see it’s alright how I’ve connected the vacuum lines?
Thank you very much to you and Simon for the help.
I assume as it’s a 250efi engine & yours was a carb bikes your using the carbs from the 125?
Yes, but I’ve changed the main jets on the carburetors to FRONT = 92.5, REAR = 95, and I’ve put the pilot jets at 20.
I forgot to mention that the bike is a Hyosung GT125R with a 250 engine. Because the 125 died and i had a 250 EFI near for a replace.
Hi, I forgot to mention that the EFI engine worked well with carburetors. I replaced the stator and the rotor to get it running.
Thanks. 😀
Does the Hyosung GT125R ’10 have a rev limiter? I’ve revved it to 13k and got scared. 😐
10,000 rpm is more than enough as there is no power after 11k rpm. Valves Start floating & crank gets more rapid wear if bike is always at 11k + rpm , so to keep her healthy 10k max is good. We rarely need to go beyond 10k , even people on 650s here in UK. A vtwin makes peak power lower revs but Gt125 will peak at 10k. but yes there No rev limiter.
I usually do not exceed 10,500 rpm. I find it strange that Hyosung decided not to include a rev limiter, as the CDI changes the pre-ignition depending on the RPM range, correct? Is this common in motorcycles?
I ended up using my power tool; I don’t like those noisy things, but I had no choice.
There’s no reason it won’t work, they are the same engine the efi stator is a higher output that’s the only thing I can think of. You have the carbs, manifolds, wiring etc should just fit right in.
Replace the stator of EFi to Carby Stator , so use your old carby stator And also use your CARBY flywheel This is because the EFi flywheel does not work with Carby CDi’s Next thing, use Size 20 pilot jets and 92.5 + 95 main jets See full tutorial of jetting here
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
Don’t throw away the old 250 engine, you will NEED IT for spare parts in future 🙂
Can you give me a hint on how to loosen the flywheel nut? The manual says that I have to lock the connecting rod with something, but I don’t want to remove the cylinder head, cylinder, and piston.
Sounds like weak battery if it can’t handle lights being ON and trying to crank it at the same time. I would recommend a fresh battery from halfords or SportsBikeShop website (trusted) , to get YUASA YTX 14BS , little batteries degrade faster and will soon mean new starter motor and relay , engine is happy when battery has around 200CCA capacity to crank considering its a thirsty 2 piston vtwin. Then confirm yourself or replace regulator or stator unit , if the following fails (even korea says change it too in their manuals) – Idle Voltage = 14V DC (max 15v/14.8) —> Lowest accepted 13.6V – 5,000 rpm voltage = 14v-15v (If it is 13.xx above 3,000 rpm, replace regulator, it will burn)
Try with or without lights
Try with jumper cable.
I guess it’s a battery issue.
But I forgot to use the multimeter to test the regulator.
The fact it’s both sides messing around says its probably the connector blocks behind the headlight unplug spray with contact cleaner, the starter switch could be the side stand switch playing up.
Lights going dimm when pressing start usually means either of these:
- Tank Tap has burst,causing fuel to keep flowing to the carb , causing cylinders to hydrolock (dangerous), remove “OIL FILLER” plug on your clutch cover and sniff hard. if you smell fuel, drain oil, replace oil filter, service the carb, replace intake orings , and definitely replace the tap Or Lift tank safely , and cover electronics (be wise!!) , disconnect fuel pipe from the tap and see if tap bursts fuel in to bucket while bike is totally off. I say use extreme caution as petrol fumes near battery can easily cause instant flames should spillages happen. You have been warned 😬
- Relay is burst (common)
- Battery too old or weak. Get it tested free at halfords or bike shop with their own “specialized bettery gauges”
- Battery too small (too low CCA to crank 2 pistons)
- Charging system wanning (causing battery to have low volts to start next time) common culprit is a regulator (which can annoy the stator next and kill it)
- Starter Motor too old (last but not least, but it is not uncommon)
Good luck and see about doing what Simon said above ^
Hi again, I recently noticed that if I turn off the light switch, the bike starts with the first push of the start button.
PS: I don’t think it’s hydrolock because the bike starts after pushing the start button 3 to 5 times with the light on. Also, I don’t believe it’s a battery issue because when the starter begins cranking, it performs very well.
The fact it’s both sides messing around says its probably the connector blocks behind the headlight unplug spray with contact cleaner, the starter switch could be the side stand switch playing up.
Thanks, I will do that and update with the results.
P.S.: I already bypassed the side stand switch because it was causing my bike to shut down while riding, haha.Also, today I noticed that when I press the start button and the bike does not start, I can see the neutral bulb dim, and I can’t hear the starter relay either. It could be the starter relay, but that does not explain the horn button issue.
We do not see a video link? Mixture is 2.5 full turns from closed. Do not adjust this ever again because it is very difficult to optimize if bike has other issues. So if bike has issues after 2.5 turns. Dont turn it again. Replace jets and have the carb ultrasonic cleaned. Then look for cracks in intake rubber manifolds.
- Sometimes it helps to replace intake manifold O-RINGS (like the ones you see at our shop)
Regarding airbox fitting…. 1. Attach carbs to airbox 2. Tighten clamps holding carb to airbox 3. Airbox & Carb together will slowly (slowly!) Go inside intake rubber manifolds 4. Make sure manifolds do not get stressed. Be very gentle with that as they are very difficult rubber parts to buy. Korea stopped making them.
Yes, I intend to change the intake o-rings. I have looked in the store and it seems that you do not ship to Spain, right?
I’d just seal it up with a sheet of 3mm plastic. Avoid using through bolts if you can. You don’t want hardware going through the engine.
The hyosung doesn’t like pod filters, many of us worldwide have tried to use pods but the bike becomes unstable and its a very frustrating war of messing with the carbs everyday. Trust me, the airbox wins. As Jim said above ^ , why not a metal/plastic sheet there and use “JB WELD EPOXY HIGH TEMP” for plastic. This could be the cheapest and easiest solution. No screws. Otherwise it may rattle and end up inside the engine and it explodes , very good advise from Jim
Ok, I have glued the hole with a plastic sheet and glue that says it can withstand 100ºC.
But it still goes bad. I have recorded a video, the motorcycle starts cold without the need for the choke. I also noticed that the AIS hose was not attached to the airbox but is attached to the exhaust. Plus it does a lot of “pop pop pop pop”. The intake nozzles are cracked.
Well, in the video it looks like the bike is going well, until at one point it seems to die but it recovers and finally dies suddenly.
At minute 0:30 and 1:18.
I suspect that the previous owner has messed up with the screws of the pilot jets.
At the moment I have ordered a gasket kit to clean the carburettor.
Regarding the intake nozzles, do I cover them in silicone?
Oh, by the way, putting the airbox in has been a pain. Any advice for next time?
Thanks again.
I’d just seal it up with a sheet of 3mm plastic. Avoid using through bolts if you can. You don’t want hardware going through the engine.
The hyosung doesn’t like pod filters, many of us worldwide have tried to use pods but the bike becomes unstable and its a very frustrating war of messing with the carbs everyday. Trust me, the airbox wins. As Jim said above ^ , why not a metal/plastic sheet there and use “JB WELD EPOXY HIGH TEMP” for plastic. This could be the cheapest and easiest solution. No screws. Otherwise it may rattle and end up inside the engine and it explodes , very good advise from Jim
Ok, I’ll do that, today I’ll probably go to the garage. As soon as I fix it, I’ll update.
Thank you so much.
Can you show us a picture if possible to see what kind of damage the last owners did to it ? We have airboxes on ebay and happy to ship worldwide. Maybe there is a way to fix yours if possible ? but try attach a picture here if you can
I have drawn it with paint, all the area with gray is cut off.
I was wondering that since the air box is cut, wouldn’t it be better to put this type of air filter and change the main jets of the carburetor?
Do you see it as a good idea?
Thanks for the reply.
