3
I did some research and these injectors are meant to be paired up with the Yuminashi bore kits.
They have injectors meant for the 150cc kit, and the 150cc+ kits.
![]()
This Light Bore High Performance Fuel Injector looks exactly the same as your genuine MSX125 fuel injector, and you only can see, or better said, feel, the difference once you have installed it on your MSX125 in combination with the Yuminashi 145cc Light Bore Piston set (to bore your genuine 125cc cylinder up to 145cc), or with the full 150cc light bore cylinder kit.
This injector is not mentioned to be installed in the 31mm throttle body, but very simply to replace your genuine 125cc injector in your genuine 125cc manifold.
Like this you don't need to buy any electronic device for your PGM-FI to upgrade your stock 125cc until a light bore 145cc or 150cc.
**The Light Bore High Performance Fuel Injector is not recommended to be used in a full stock 125cc MSX125 engine...
![]()
This High Performance Fuel Injector is mentioned to be used on the Big Bore kits in combination with the big valve heads.
These High Performance Fuel Injectors are looking exactly the same at first sight as your genuine MSX125/GROM injector, but have 2 extra holes that you need if you start to work with the larger, +150cc displacement Big-Bore cylinder kits.
These injectors don't fit in our 3-sensor PGM-FI 31mm throttle body, but can perfectly be used in combination with our 34mm PGM-FI 3-sensor throttle body.
**This injector would fit in your genuine MSX125, but is overkill on an engine less as 160cc...
If you start to work with the Big-Bore or Super-Bore cylinder kits, then keep in mind that you need to check, and control the AFR ratio (Air Fuel Ratio) from your engine, not only to improve the performance, but also to keep your engine alive.
We recommend an AFR ratio from 13.2:1 (this means the stoichiometric Air–Fuel Ratio (mixture) where for every gram of fuel, 13.2 grams of air are required).
The Air Fuel Ratio inside your engine is changing all the time, and we know from experience that in a high performance engine with a high-lift/ longer duration cam like the Yuminashi SX270 camshaft, a peak at high engine load of 14:1 is allowed.
Anything higher as 14:1 at high engine load will increase the risk on detonation/pre-ignition dramatically, where you blow a hole in your piston as soon as you hit the 15:1.
To avoid this, you need to install our High Performance fuel injector on the big bore and super bore kits, and you need to check then your AFR ratio to see where you are.
If your AFR ratio is to high, which means a to lean stoichiometric air-fuel mixture, then you will need an electronic device to correct it.
**Make sure that you are checking your AFR ratio with a wide band O2 sensor. The narrow band sensor like the MSX125/GROM and all motorcycles have installed standard is useless to measure the accurate AFR ratio.
They also sell a 31mm throttle body set
![]()
This 3-Sensor YUMINASHI 31mm PGM-FI Throttle Body (MAP sensor (Manifold Absolute Pressure Sensor), IAT Sensor (Air Intake Sensor), TP Sensor (Throttle Position Sensor) with EACV (Idle Air Control Valve)), is mentioned to bring your simplified 1-sensor genuine MSX125 / GROM PGM-FI system without an Idle Air Control Valve and only a TP Sensor to a higher level and ready to be used to get the best optimal performance/potential out of your engine.
This set comes complete with all sensors installed, inclusing the High Performance Fuel Injector and the Idle Air Control valve, plug & play ready to be programmed (if you have a programable ECU unit) to achieve the best possible results...
This throttle body has to be used with a special wire harness, and 3-sensor racing ECU and the YUMINASHI 31mm PGM-FI Manifold Set for Honda MSX125 / Honda GROM.
The venturi is machined in to a stack to optimise and achieve an improved velocity. The entire inside of the throttle body is mirror shine polished.
**For racing applications best performance will be achieved without air filter. For road use we recommend original air filter K&N R-1100.
They have injectors meant for the 150cc kit, and the 150cc+ kits.
This Light Bore High Performance Fuel Injector looks exactly the same as your genuine MSX125 fuel injector, and you only can see, or better said, feel, the difference once you have installed it on your MSX125 in combination with the Yuminashi 145cc Light Bore Piston set (to bore your genuine 125cc cylinder up to 145cc), or with the full 150cc light bore cylinder kit.
This injector is not mentioned to be installed in the 31mm throttle body, but very simply to replace your genuine 125cc injector in your genuine 125cc manifold.
Like this you don't need to buy any electronic device for your PGM-FI to upgrade your stock 125cc until a light bore 145cc or 150cc.
**The Light Bore High Performance Fuel Injector is not recommended to be used in a full stock 125cc MSX125 engine...
This High Performance Fuel Injector is mentioned to be used on the Big Bore kits in combination with the big valve heads.
These High Performance Fuel Injectors are looking exactly the same at first sight as your genuine MSX125/GROM injector, but have 2 extra holes that you need if you start to work with the larger, +150cc displacement Big-Bore cylinder kits.
These injectors don't fit in our 3-sensor PGM-FI 31mm throttle body, but can perfectly be used in combination with our 34mm PGM-FI 3-sensor throttle body.
**This injector would fit in your genuine MSX125, but is overkill on an engine less as 160cc...
If you start to work with the Big-Bore or Super-Bore cylinder kits, then keep in mind that you need to check, and control the AFR ratio (Air Fuel Ratio) from your engine, not only to improve the performance, but also to keep your engine alive.
We recommend an AFR ratio from 13.2:1 (this means the stoichiometric Air–Fuel Ratio (mixture) where for every gram of fuel, 13.2 grams of air are required).
The Air Fuel Ratio inside your engine is changing all the time, and we know from experience that in a high performance engine with a high-lift/ longer duration cam like the Yuminashi SX270 camshaft, a peak at high engine load of 14:1 is allowed.
Anything higher as 14:1 at high engine load will increase the risk on detonation/pre-ignition dramatically, where you blow a hole in your piston as soon as you hit the 15:1.
To avoid this, you need to install our High Performance fuel injector on the big bore and super bore kits, and you need to check then your AFR ratio to see where you are.
If your AFR ratio is to high, which means a to lean stoichiometric air-fuel mixture, then you will need an electronic device to correct it.
**Make sure that you are checking your AFR ratio with a wide band O2 sensor. The narrow band sensor like the MSX125/GROM and all motorcycles have installed standard is useless to measure the accurate AFR ratio.
They also sell a 31mm throttle body set
This 3-Sensor YUMINASHI 31mm PGM-FI Throttle Body (MAP sensor (Manifold Absolute Pressure Sensor), IAT Sensor (Air Intake Sensor), TP Sensor (Throttle Position Sensor) with EACV (Idle Air Control Valve)), is mentioned to bring your simplified 1-sensor genuine MSX125 / GROM PGM-FI system without an Idle Air Control Valve and only a TP Sensor to a higher level and ready to be used to get the best optimal performance/potential out of your engine.
This set comes complete with all sensors installed, inclusing the High Performance Fuel Injector and the Idle Air Control valve, plug & play ready to be programmed (if you have a programable ECU unit) to achieve the best possible results...
This throttle body has to be used with a special wire harness, and 3-sensor racing ECU and the YUMINASHI 31mm PGM-FI Manifold Set for Honda MSX125 / Honda GROM.
The venturi is machined in to a stack to optimise and achieve an improved velocity. The entire inside of the throttle body is mirror shine polished.
**For racing applications best performance will be achieved without air filter. For road use we recommend original air filter K&N R-1100.
