Just got my hands on “new” bike and I need help – GT250
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Bike Model = : Comet 250GT
Hello!
Today I bought a bike for the first time in my life, and it’s not even mine. I got it for my girlfriend who is just about to finish the biking school.
I bought a Hyosung GT250 for around 1000€ (felt like a steal for me) knowing it has some issues (the charging regulator is blown) and a dead battery (or, I just assumed these were the only issues)
When i got at the place, after a 4-hour drive, found out that the motorcycle had a FI system equipped from factory, and it was swapped with a carby (including the CDI and main harness from a carby GT250).
I want to switch back to injection, since the previous owner gave me the original main harness, with one CDI and the original ECU, and everything else that was on the bike.
Now, i have the feeling that the original main harness might have been chopped here and there in order to make the swap possible.
Does anybody have and is willing to share a complete wiring diagram with me?
Also, to be mentioned that the cluster doesnt work. The only light thats coming on is the Neutral light. Even the display isn’t working.
Thank you!
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I would stay on the carb system as the FI system on the 25o means you have a lot of EFi parts to stay on top of. Carby is better as its less maintenance and less worry, it’s just better. However, in regards to your cluster , post a picture so we see what it looks like first.
If still wanting to go EFi , check the wiring tables posted by another member in this forum , including this too https://hyoriders.club/fuel_induction_manual/
Also wiring diagrams vary wildly so choose the appropriate manual (on this forum) or ManualsLIB site , Hyosung used 4 different harness on EFI models and 4 different ECU, they use different sensors , it is a big thing to match everything right or you get problems trying to run things properly. Common now is DELPHI ECU (it will say it on the ECU) and uses Delphi Harness (2013-2015) and Delphi V2 harness (different connectors and more fuses) (2016-2019)
Older ECU is not possible anymore (Sentec, Daewoo, etc due those companies not existing anymore) – Hyosung is using Delphi Electronics going forward , you need a tank that accepts EFi pumps too, and possible EFi throttle bodies and a wide array of sensors, EFi air box, injectors , Exhaust should have 2 ports for lambda (Delphi later models) or 1 lambda port for older Delphi or older ECUs .
Though It is hard to comment further until you provide pictures and details of what you have laying on the floor , and possible tell you what system you have.
If the harness has been chopped up , it can be saved but be suspicious! There is a reason carby was better outcome for the bike probably and Regulators are common fault for ALL OEM Hyosung and Chinese Junk ones. Use a TrueMOSFET one such as SHINGDEN Japan , if not , just visit ElectroSport USA , they make an “OK-ish” regulator for the bike.
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I would stay on the carb system as the FI system on the 25o means you have a lot of EFi parts to stay on top of. Carby is better as its less maintenance and less worry, it’s just better. However, in regards to your cluster , post a picture so we see what it looks like first. If still wanting to go EFi , check the wiring tables posted by another member in this forum , including this too https://hyoriders.club/fuel_induction_manual/ Also wiring diagrams vary wildly so choose the appropriate manual (on this forum) or ManualsLIB site , Hyosung used 4 different harness on EFI models and 4 different ECU, they use different sensors , it is a big thing to match everything right or you get problems trying to run things properly. Common now is DELPHI ECU (it will say it on the ECU) and uses Delphi Harness (2013-2015) and Delphi V2 harness (different connectors and more fuses) (2016-2019) Older ECU is not possible anymore (Sentec, Daewoo, etc due those companies not existing anymore) – Hyosung is using Delphi Electronics going forward , you need a tank that accepts EFi pumps too, and possible EFi throttle bodies and a wide array of sensors, EFi air box, injectors , Exhaust should have 2 ports for lambda (Delphi later models) or 1 lambda port for older Delphi or older ECUs . Though It is hard to comment further until you provide pictures and details of what you have laying on the floor , and possible tell you what system you have. If the harness has been chopped up , it can be saved but be suspicious! There is a reason carby was better outcome for the bike probably and Regulators are common fault for ALL OEM Hyosung and Chinese Junk ones. Use a TrueMOSFET one such as SHINGDEN Japan , if not , just visit ElectroSport USA , they make an “OK-ish” regulator for the bike.
As far as I could document myself in one day, its running on the first gen of Daewoo CDI and harness.
Currently, I have put back on the bike half of the EFI harness, and also mounted the throttle bodies. I have to re-make the fuel lines and vac system since the previous owner took it all out, and i would really need some help(pictures of a standard one) to get it done.
I will try to take the CDI to my workplace, since we have some electricians that could try to fix it. If not possible, I will accept my defeat and switch it back to carburetor(and do it right this time, since it was all messed up) and hoping it would start.
Couldnt start it up anymore since i got home, but the guy I bought it from started it right up.
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Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them.
airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies.
The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
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Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them. airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies. The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
Okay, but what about the return line? I cant figure it out.
Thanks a lot!
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Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them. airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies. The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
Okay, but what about the return line? I cant figure it out. Thanks a lot!
have to see what your setup looks like, not all needed and it’s complicated to give a straight answer due to differences between the older and newer pumps and wether the past owners have made modifications to the fuel railing systems such as using a Kemso aftermarket pump or changes to the pressure relief valves on the pumps.
The older black pumps had different pressure ratings and had 1 pipe ==2 pipes ==then single pipe down to the frame == then 2 final pipes to either throttle body where the injector is.
Most of the time , you will see a single hose leaving the pump going to the middle section of the bike frame. It breaks off in to Front Pipe and Rear Pipe after that junction. The 250 is a little less complicated than the 650 thankfully.
You will deal with more air pipes for the throttle bodies , air lines from airbox to Electric Valve Pump which sends even more air down the exhaust pipes (emissions control) (Some bikes out of UK actually have far more , like the american versions for some kind of extra emissions control) , more pipes from either engine cylinder going in to the airbox etc.
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Doo a deep dive in your area to find any wrecked 250 EFi, they would be great for parts. Daewoo uses an OEM black pump that has a different pressure rating (harder to find) , Delphi pumps are OEM Blue and have OEM numbers printed on them. airbox EFi has port to slot in the ISC valve (idle speed controller) , and it sends 2 air pipes down to the throttle bodies. The pump splits 1 fuel pipe in to a T-Piece which joins 2 smaller pipes feeding either injector (front + rear )
Okay, but what about the return line? I cant figure it out. Thanks a lot!
have to see what your setup looks like, not all needed and it’s complicated to give a straight answer due to differences between the older and newer pumps and wether the past owners have made modifications to the fuel railing systems such as using a Kemso aftermarket pump or changes to the pressure relief valves on the pumps. The older black pumps had different pressure ratings and had 1 pipe ==2 pipes ==then single pipe down to the frame == then 2 final pipes to either throttle body where the injector is. Most of the time , you will see a single hose leaving the pump going to the middle section of the bike frame. It breaks off in to Front Pipe and Rear Pipe after that junction. The 250 is a little less complicated than the 650 thankfully. You will deal with more air pipes for the throttle bodies , air lines from airbox to Electric Valve Pump which sends even more air down the exhaust pipes (emissions control) (Some bikes out of UK actually have far more , like the american versions for some kind of extra emissions control) , more pipes from either engine cylinder going in to the airbox etc.
Alright, from what you said, I found out that my model doesn’t have a return line.
Yesterday I stripped the wiring loom for the injectors+throttle body sensors and found out that the some wires were broken, the wires for the injectors had the insulation melted (probably from touching the engine) and covered up + some weak connections. Soldered everything up and insulated them very well and hoping not to have to do this to the main harness, also hoping that the injector wires didn’t generate a short and fry the CDI.Fuel lines are done, I just need to do the air lines from the air box, add a fuel filter, finish swapping the carby wiring loom with the EFi (about 50% done), check for spark, add a new battery and crank it up. Hope I can get it starting this week.
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1st pic is hard to tell but , focus on the ECU and relays first , then go down to the front, less headaches that way actually. Better to work from the back as connectors will be more self explanatory (rear eg = relays , lights , thats it. there is a 2 pin socket next to relay, leave it. and another 4pin socket hiding itself inside a black jacket, ignore)
If not, more pictures will explain it better.2nd image = there is a little white plug with 1 brown and 1 green wire = Engine temp sensor ,
ET sensor sits at the front cylinder head under the throttle body.
Take your time. Also this may help (it is for a 650 but use it as a guide to follow where most parts connect to) (especially where it says “DASH CONNECTIONS”) https://hyoriders.club/forums/topic/wiring-tables/
You noted speedo problems. The link above ^ may verify your harness connectors towards the dash itself.
Then follow the wire colours down your harness, if a dash says “Blue/RED & GREEN” this is 2 wires in a 2-pin plug, it will say fuel gauge, find it on the harness and collect the fuel gauge sensor on the tank
Blue wire from the dash on its own (example) , might say “Neutral” , find it on the harness near the middle so it can reach the N Sensor on the engine, the N Sensor will have 2 wires , the extra wire is for the ECU + Signal to trigger the starting processing (not all 250’s have the same harness or ECU, hence again i can’t always give an easy answer but generally in my experience touching every ECU i got my hands on, DAEWOO is more fussy, very fussy! – excercise patience if you can and do 1 small thing at a 1 as it helps you study too )
I am sure this forum and manualsLIB already have 250 manuals with wiring diagrams at their last pages of the PDF documents. Or even look at the 2008-2009 650GT (It uses a daewoo ECU , only a few of of its parts will work on 250 , so it gets easier to follow. Ie. 650 EFi and 250 EFi early model use the same neutral switch , same clutch switch, the manuals will tell what colour wires they are. Other things like Fan Control, Thermo Switch, etc don’t apply to 250cc as it doesn’t use water cooling.
Hope this helps and good luck!
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