Umbau von Gt125r motor auf GT250 Motor
- This topic has 29 replies, 3 voices, and was last updated 5 months, 2 weeks ago by
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If its an EFi 250cc , you need the full donor bike (EFi Tank, All electronics, Exhaust because it has lambda sensors , EFi airbox, EFi dash)
This is assuming you are using an EFi 250.
Otherwise if it is a carb model, upgrade your 125cc jets to 250cc one and keep using the 125 vacuum pump (that electric pump in picture is worthless = too many problems that’s why Hyosung used vacuum pump on all carb models after this)
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It is a 250 Naked Model from 2005 with Mikhuni Carbs.
I Read that 250 musst have a elektric full Pump…
I heard the 250 needs an electric fuel pump to keep up with fuel delivery at higher RPMs.
Can I use the vacuum pump, tank, and the rest of the setup exactly like on my 125cc?But doesn’t the 125cc have a narrower intake manifold with one of those nipples in it?
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If I convert to vacuum, can I use the intake hoses from the 125? With the carburetor setup from the 250?
Yes you can.
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Use 250 jets pilots and mains, because of bigger pistons, or it will be lean and burn a hole in the piston.
Don’t worry about the vacuum pump, all 125 / 250 are using 650cc pump – Hyosung uses a 650cc pump on their 125/250 motors. So if a GV650 can use the vacuum pump, your 250 will never max it out.
Good luck!
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Should I only change the main jet and pilot jet?
Because according to Hyosung’s technical data, I also need to change the main air jet, needle jet, and starter jet.
I wanted to raise the needle and install a sports air filter.
I also have a 95 and a 98 main jet; would that work as an upgrade, or does it have to be a 95 and a 97.5?
Thanks for your help, and I’ll let you know how it goes.
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The first carburetor is from the 125cc, while the second image shows the one from the 250cc.
Since I’m converting to a vacuum system, I noticed the 125cc carburetor has differences that the 250cc doesn’t. Do I need to use the 125cc carburetor body and install all the internals and controls from the 250cc into it?
Since I see this on the 125cc carburetor, I assume it’s also part of the vacuum system, right?”
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Your just have older style carb, use the 125cc as it is updated. It has jet pump on the side. It is not critical , but helps a little bit on throttle that is all.
Coils = Same for all GT/GV carby models for 125 and 250cc. You will be fine. Otherwise, take 250 electrics and put it in 125 if you’re worried and keep the old 125parts for spare.
Service manual will tell you more on electrics if you want to check coil & stator resistance etc.
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It’s likely not necessary because it only activates with full throttle and doesn’t pump continuously; it’s probably just for priming before the first start.
Alright, if it’s not strictly necessary, I’ll just leave the 250cc carburetor in.
Installed the 250cc carb using 125cc intake hoses to maintain vacuum delivery.
Okay, if you say the electronics are all identical, including the coils and everything, then I’ll leave it just as it is.
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- You cannot reply to this topic.
- This topic has 29 replies, 3 voices, and was last updated 5 months, 2 weeks ago by .
-
Posts
-
-
-
-
-
-
If its an EFi 250cc , you need the full donor bike (EFi Tank, All electronics, Exhaust because it has lambda sensors , EFi airbox, EFi dash)
This is assuming you are using an EFi 250.
Otherwise if it is a carb model, upgrade your 125cc jets to 250cc one and keep using the 125 vacuum pump (that electric pump in picture is worthless = too many problems that’s why Hyosung used vacuum pump on all carb models after this)
-
It is a 250 Naked Model from 2005 with Mikhuni Carbs.
I Read that 250 musst have a elektric full Pump…
I heard the 250 needs an electric fuel pump to keep up with fuel delivery at higher RPMs.
Can I use the vacuum pump, tank, and the rest of the setup exactly like on my 125cc?But doesn’t the 125cc have a narrower intake manifold with one of those nipples in it?
-
-
-
-
If I convert to vacuum, can I use the intake hoses from the 125? With the carburetor setup from the 250?
Yes you can.
-
-
-
-
-
Use 250 jets pilots and mains, because of bigger pistons, or it will be lean and burn a hole in the piston.
Don’t worry about the vacuum pump, all 125 / 250 are using 650cc pump – Hyosung uses a 650cc pump on their 125/250 motors. So if a GV650 can use the vacuum pump, your 250 will never max it out.
Good luck!
-
Should I only change the main jet and pilot jet?
Because according to Hyosung’s technical data, I also need to change the main air jet, needle jet, and starter jet.
I wanted to raise the needle and install a sports air filter.
I also have a 95 and a 98 main jet; would that work as an upgrade, or does it have to be a 95 and a 97.5?
Thanks for your help, and I’ll let you know how it goes.
-
-
-
-
-
The first carburetor is from the 125cc, while the second image shows the one from the 250cc.
Since I’m converting to a vacuum system, I noticed the 125cc carburetor has differences that the 250cc doesn’t. Do I need to use the 125cc carburetor body and install all the internals and controls from the 250cc into it?
Since I see this on the 125cc carburetor, I assume it’s also part of the vacuum system, right?”
-
-
-
-
Your just have older style carb, use the 125cc as it is updated. It has jet pump on the side. It is not critical , but helps a little bit on throttle that is all.
Coils = Same for all GT/GV carby models for 125 and 250cc. You will be fine. Otherwise, take 250 electrics and put it in 125 if you’re worried and keep the old 125parts for spare.
Service manual will tell you more on electrics if you want to check coil & stator resistance etc.
-
It’s likely not necessary because it only activates with full throttle and doesn’t pump continuously; it’s probably just for priming before the first start.
Alright, if it’s not strictly necessary, I’ll just leave the 250cc carburetor in.
Installed the 250cc carb using 125cc intake hoses to maintain vacuum delivery.
Okay, if you say the electronics are all identical, including the coils and everything, then I’ll leave it just as it is.
-
-
-
-
-
- You cannot reply to this topic.