Genuine Control Module (Speed Controller) for Razor MX125 Dirt Rocket & SX125 McGrath — Part #W15118260015

The control module — also referred to as the speed controller — is the electronic brain of the MX125 and SX125's drivetrain. It sits between the battery, the throttle, and the motor, interpreting the rider's throttle input and delivering precisely the right amount of current to the motor to produce smooth, proportional acceleration. Without a functioning control module, the motor receives either no power at all, or uncontrolled full power — neither of which allows the bike to be ridden safely.

Control module failures are among the most common electronic faults on the MX125 and SX125, and the symptoms are distinctive: the bike clicks when the throttle is applied but the motor does not turn; the motor runs at full speed with no throttle control; or the bike powers on but refuses to move despite a fully charged battery and a functioning motor. In each case, the control module is the first component to investigate after ruling out the battery and throttle.

This is the genuine Razor factory replacement control module for the MX125 Dirt Rocket and SX125 McGrath (Versions 1–5 for the SX125; all versions for the MX125), supplied with the mounting screws included. It is a direct, plug-in replacement for the original unit, using the same 5-connector wiring configuration as the factory-fitted module — ensuring that the bike's throttle response, motor protection, and speed control are restored exactly as designed

Genuine Factory Specification — Built to the exact electrical specification of the original control module, ensuring that the motor receives the correct current profile for smooth, proportional throttle response. Aftermarket controllers frequently deliver on/off power rather than true variable speed, fundamentally changing the riding experience and removing the progressive acceleration that makes the MX125 and SX125 safe and enjoyable for younger riders.

5-Connector Plug-In Replacement — The genuine module uses the same 5-connector wiring configuration as the original, ensuring a direct plug-in replacement with no wiring modifications, splicing, or adapter cables required. Each connector is keyed to prevent incorrect installation.

Built-In Motor Protection — The genuine control module incorporates overcurrent and thermal protection circuits that prevent the motor from being damaged by sustained overload. Aftermarket modules frequently omit these protections, leaving the motor vulnerable to burnout under heavy use.

Supplied with Mounting Screws — All mounting screws are included, ensuring a secure, vibration-resistant installation without the need to source additional hardware.

Resolves the Most Common Electronic Failure on the MX125 and SX125 — The control module is statistically the most frequently replaced electronic component on both models. Replacing it with the genuine part is the definitive repair for a bike that clicks but does not move, or that has lost throttle control

Razor MX125 Dirt Rocket 
All versions (V1+)
Razor SX125 McGrath 
Versions 15

SX125 version check — important: The SX125 McGrath introduced a revised controlmodule from Version 6 onwards (Part #W13112260030), which is not compatible withthis part. Always confirm your SX125 version before ordering.How to identify yourversion: Locate the barcode sticker on your battery cover or the bottom of the frame. The7th and 8th digits of the product ID code indicate your version number (e.g., "01" =Version 1, "06" = Version 6).Not compatible with: Razor MX350, MX400, SX500, or anyother Razor dirt bike model — all of which use different control modules with differentvoltage ratings and connector configurations.