Honda Grom ECU Reflash

Unlock smoother, stronger power delivery from your Honda Grom/MSX125 with our basic Stage 1 ECU reflash, designed specifically for stock engines or those with light bolt-on modifications such as an aftermarket intake or a higher-flow exhaust. This service is not intended for complex engine builds such as big bore kits, high-compression pistons, aggressive camshafts, or other advanced performance setups. From the factory, these bikes tend to run lean, especially when fitted with aftermarket exhaust or intake systems. Our calibration addresses this by improving fueling for better performance, smoother throttle response, and a safer air/fuel ratio. What This Tune Does Our Stage 1 reflash makes subtle yet effective improvements to your ECU’s calibration: Slight ignition timing adjustments in select conditions and RPM ranges for crisper throttle response. Refined fuel mapping to smooth out power delivery and improve rideability. Increeased rev limiter to 9,500 RPM Expanded closed-loop fuel trim range, allowing the O₂ sensor to make broader corrections during normal cruising for better adaptability. Optional Features At the time of service, you can request any of the following adjustments: Disable O₂ sensor feedback (disables closed-loop mode entirely). Disable tip-over sensor (for track or custom applications where it is not desired) Compatible ECU Part Numbers This service is compatible with the following OEM Honda ECUs: 38770-K26-901 38770-K26-911 38770-K26-921 38770-K26-B02 38770-K26-B13 38770-K26-B42 38770-K26-C01 38770-K26-C31 38770-K26-G01 38770-K26-G11 38770-K26-M01 How It Works Purchase this reflash service through our website. Send in your ECU to our shop for programming (Fill out service form for instructions). We perform the reflash and return your ECU ready to install. Important Notes This is a basic reflash, intended for stock or lightly modified Grom/MSX125 engines. Not for use with advanced engine builds requiring full custom tuning. Intended for off-road/competition use where emissions compliance is not required.