How to Upgrade Your Razor MX650 or SX500: The Complete Electro & Company Guide How to Upgrade Your Razor MX650 or SX500: The Complete Electro & Company Guide

How to Upgrade Your Razor MX650 or SX500: The Complete Electro & Company Guide

Your Razor MX650 or SX500 is an excellent foundation for a high-performance electric pit bike—but building it correctly means doing more than installing the biggest motor you can find.

At Electro & Company, we design our power kits, batteries, brakes, suspension, wheels, and drivetrain components to work together as a complete system. In this guide, we’ll walk you through your upgrade options by component and explain the best order to build your bike.

Product prices, specifications, lead times, and availability can change. Always review the linked product page and select the options that match your exact bike, wheels, swingarm, battery, and intended use before ordering.

Before You Begin: MX650 Versus SX500

Most of our power kits, brake systems, forks, wheels, and swingarm extensions fit both the Razor MX650 and SX500. The most important model-specific difference is the rear suspension:

Your rear-wheel diameter also affects gearing. A sprocket combination designed for a 10-inch rear wheel should not automatically be used with a 12-inch wheel.

Our high-performance kits can produce motorcycle-level acceleration and speeds far beyond the stock bike’s original design target. Always wear appropriate protective equipment, inspect your bike before every ride, and ride only in permitted areas.

The Best Order to Upgrade Your Razor

For most MX650 and SX500 builds, we recommend upgrading in this order:

  1. Inspect and service the stock chassis.
  2. Upgrade both brakes.
  3. Choose your final wheel and tire configuration.
  4. Upgrade the fork and install the correct model-specific rear shock.
  5. Add swingarm extensions if your wheel or motor configuration requires them.
  6. Choose your complete power kit.
  7. Install the matching battery, controller, motor, and drivetrain.
  8. Add your display, charging equipment, lighting, and cockpit accessories.
  9. Test your bike in its lowest power mode before increasing performance.

Following this order helps you avoid one of the most common build mistakes: making your Razor extremely fast before its brakes, suspension, wheels, gearing, and chassis are ready for the additional speed.

1. Baseline Inspection and Chassis Preparation

Before adding performance parts, inspect:

  • Frame welds and mounting points
  • Steering bearings
  • Swingarm bushings and pivot hardware
  • Wheel bearings
  • Axles and fasteners
  • Brake mounts and rotors
  • Chain alignment
  • Tires and tubes
  • Battery tray and enclosure area

Replace worn or damaged components first. A loose bearing, damaged frame, or misaligned drivetrain becomes much more serious at 45–60+ mph.

You should also decide whether you want an off-road, mixed-terrain, or Supermoto build. That choice will affect your wheels, fork, swingarm, brake hardware, sprockets, and final gearing.

2. Brakes: Your First Performance Upgrade

We recommend upgrading your brakes before—or at the same time as—your power system.

Razor/ETM 4-Piston Hydraulic Brake Kit

Our Razor/ETM 4-Piston Hydraulic Brake Kit is an excellent starting point for an upgraded MX650 or SX500.

The kit includes:

  • Front and rear four-piston hydraulic brakes
  • Brake rotors
  • Caliper mounts
  • Necessary installation hardware

Four-piston calipers provide a larger pad-to-rotor contact area, stronger clamping pressure, and improved heat dissipation compared with the stock braking system.

This is the minimum brake upgrade we recommend for a bike running our Ultimate 5000W Razor Kit V3.0.

You can learn more about why we developed this system in our published article, 4 Piston Razor Brakes!?.

Extreme Hydraulic Brake Kit

For high-speed, heavier, or aggressively ridden builds, we recommend our Extreme Razor/ETM Hydraulic Brake Kit.

This system uses larger calipers and thicker custom rotors to provide increased stopping power and heat management. When ordering, you can select the appropriate configuration for:

  • Your front wheel
  • Your rear wheel
  • Your stock swingarm or our extended swingarm

These selections matter because the rotor configuration must match the parts installed on your bike.

The Extreme kit fits the Razor MX500, MX650, and SX500, but it does not fit the Razor Pro Spec, ETM V2, or ETM RTR.

Always install and properly bleed both brakes. Do not operate your bike with only one of the supplied brakes installed. Using a single brake can create excessive heat and lead to catastrophic failure.

3. Wheels and Tires

Choose your final wheel configuration before setting your gearing or purchasing wheel-specific brake hardware.

Razor Pit Bike Rear Wheel: Our Recommended Off-Road Rear Wheel

For an off-road MX650 or SX500 build, we recommend replacing the stock rear wheel with our Razor Pit Bike Rear Wheel.

The stock Razor rear wheel uses a factory freewheel and a light sheet-metal hub with small spokes. Our Pit Bike Rear Wheel replaces that setup with a solid ETM-style 10-inch rear hub and a direct bolt-on sprocket adapter, creating a stronger and more reliable drivetrain connection.

The kit includes:

  • 10-inch ETM rear wheel
  • Pre-mounted off-road tire
  • Billet sprocket adapter
  • Billet brake-rotor adapter
  • Billet wheel spacers
  • Billet brake hanger for our swingarm extensions
  • 160mm brake rotor and hardware
  • 180mm brake rotor and hardware

The pre-mounted tire uses tall knobs for off-road traction, while its wider profile improves stability and control.

The wheel fits the Razor MX500, MX650, and SX500. It can be installed with:

Because the wheel replaces the stock freewheel with a solid rear hub and direct sprocket mount, it is a much better foundation for an upgraded motor and #35 drivetrain.

10-Inch Supermoto Wheels

Our Razor 10-Inch Supermoto Wheel Set is intended for pavement-oriented builds that retain a compact wheel diameter.

This configuration gives your bike a lower, more responsive Supermoto stance. You must still select motor and rear sprockets that create an appropriate ratio for a 10-inch rear wheel.

12-Inch Supermoto Wheels

Our Razor 12-Inch Supermoto Wheel Set gives your bike a taller stance, enhanced stability, and a more road-oriented feel.

The set includes a rear sprocket designed to maintain an appropriate gear ratio. However, this is not an isolated wheel swap. You must also install:

Both supporting components are required for proper clearance and integration.

Read our published article, Razor 12-Inch Supermoto Wheels Are Here!, for more information about the handling, stability, and gearing benefits.

Razor Scrambler Wheel Set

Our Razor Scrambler Wheel Set is our mixed-terrain option for riders who want off-road traction without sacrificing smooth pavement performance.

The set includes:

  • Front and rear 10-inch spoked wheels
  • Pre-mounted Scrambler tires
  • CNC sprocket adapter
  • CNC brake-caliper brackets
  • 160mm and 180mm brake rotors
  • Required installation hardware

The wheels fit the Razor MX500, MX650, and SX500. They work with either the stock MX/SX fork or our ETM V2 Razor Hydraulic Fork Upgrade Kit.

Our Razor MX/SX Swingarm Extensions are required for tire clearance.

For the full compatibility breakdown, read Razor Scrambler Wheel Set: The Best of Both Worlds.

4. Front and Rear Suspension

Additional speed quickly exposes the limitations of the stock Razor suspension. Improved suspension helps keep your tires in contact with the ground, controls weight transfer under braking, and makes the bike more stable and predictable.

ETM V2 Razor Hydraulic Fork Upgrade Kit

Our ETM V2 Razor Hydraulic Fork Upgrade Kit is a direct-fit front-end conversion for the Razor MX500, MX650, SX500, and RSF chassis.

The kit includes:

  • Hydraulic fork legs
  • 12-inch front wheel with MX tire
  • 12mm front axle
  • 180mm brake rotor
  • Brake-caliper adapter
  • Forged upper and lower triple clamps
  • Forged bar mounts
  • Low MX handlebars
  • Billet chassis adapters
  • Fork guards
  • Front fender
  • Number plate
  • Necessary installation hardware

Choose your fork length according to your build:

  • The 630mm fork is recommended for a stock-height Razor and pairs well with our swingarm extensions.
  • The 670mm fork is recommended with our Razor Big Wheel Kit, although it can also be installed on a stock-wheel Razor.

Hydraulic brakes are required to run this fork kit.

Our article Hydraulic Razor Forks, They Exist! explains the direct-fit approach behind this conversion.

MX650 Rear Shock

For an MX650, use our Razor MX Upgrade DNM Shock.

This is a 190mm DNM AO-38RC air shock with:

  • Adjustable air pressure
  • Adjustable rebound
  • Adjustable damping
  • A tuning range of approximately 250–550 pounds through air pressure

We strongly recommend pairing it with our ETM V2 Razor Hydraulic Fork Upgrade Kit to maintain balanced ride height and suspension behavior.

Do not use this shock on an SX500.

SX500 Rear Shock

For an SX500, use our Razor SX Upgrade DNM Shock.

This model-specific DNM RCP-2S shock features:

  • 220mm eye-to-eye length
  • 66mm of travel
  • Adjustable rebound
  • Adjustable damping
  • A 450-pound spring selected for the Razor platform

We selected the 450-pound spring because it is better suited to the SX500 than the excessively stiff 550-pound alternatives commonly sold elsewhere.

Do not use this shock on an MX500 or MX650.

5. Swingarm and Chassis Geometry

Our Razor MX/SX Swingarm Extensions add approximately two to three inches to the wheelbase of an MX500, MX650, or SX500.

Benefits include:

  • Increased high-speed stability
  • Additional tire and motor clearance
  • A moto-style 12mm axle
  • Adjustable axle blocks
  • More precise chain adjustment
  • Reduced chain movement and tensioner noise
  • Improved balance with the 630mm fork kit

The extension preserves a manageable balance point while giving the bike greater stability under acceleration.

Installing the extensions requires drilling your stock swingarm.

The extensions are optional for some stock-size-wheel power builds, but they are required for:

6. Power-System Options

We strongly recommend choosing a complete matched power kit instead of combining unrelated motors, controllers, batteries, wiring, and drivetrains.

Our complete kits provide known connectors, mounting solutions, controller programming, gearing guidance, and documented compatibility.

Ultimate 5000W Razor Kit V3.0: Our Best All-Around Option

Our Ultimate 5000W Razor Kit V3.0 is the most approachable complete conversion for an MX650 or SX500.

The kit includes:

  • EC4P Lite brushless motor
  • 300-phase-amp FOC controller tuned to 5,000W
  • E&C Razor #35 HD Ultralight Sprocket and Chain Kit
  • Controller mount
  • EMX Lite three-mode throttle
  • Handlebar power switch
  • Key switch and voltmeter
  • Grips
  • Wiring harnesses and battery leads
  • Optional 72V 20Ah battery and charger

The kit is designed as a plug-and-play system, with no soldering or controller tuning required.

With the listed 72V 20Ah battery, we rate the kit for 45+ mph and approximately 1.5–3 hours of average wheels-rolling ride time. A compatible 72V or 76V battery is required.

This is our recommended option if you want a major increase in speed and performance without beginning with an 11–13kW competition-style build.

You can read more about the development of this platform in:

Extreme 11,000W Razor Kit: Our High-Speed Option

Our Extreme 11,000W Razor Kit combines:

The system can deliver approximately:

  • 8kW with the 52V 20Ah battery
  • 9kW with the 72V 30Ah battery
  • 11kW with the 76V 20Ah battery
  • Up to 14kW with the 76V 24Ah battery

The kit is designed to operate best at 11kW. Although the 76V 24Ah configuration can support more power, exceeding 11kW reduces available thermal headroom.

The TruMoto app allows you to monitor and adjust the controller through a straightforward interface.

A #35 drivetrain is mandatory because The “ONE” motor does not support the smaller stock chain systems. Pair this kit with our E&C Razor #35 HD Ultralight Sprocket and Chain Kit.

For this power level, we recommend completing your Extreme brakes, suspension, rear-wheel, and chassis upgrades first.

Read EC4P and Extreme Razor Kits Are Extreme! for more information about the development and performance goals of the system.

6+7 13kW Revolver Kit: Our Maximum-Torque Option

Our 6+7 13kW Razor Upgrade Kit adapts our ETM RTR Revolver motor to the Razor MX/SX platform.

The system includes:

  • Revolver motor
  • TruMoto Little Bit V3 controller
  • Heavy-duty 420 chain conversion
  • App-based power adjustment
  • Adjustable torque delivery
  • Adjustable throttle response and throttle curve
  • Regenerative-braking adjustment
  • Live speed, RPM, voltage, power, and performance data

This is the largest bolt-in motor system we currently offer for the conventional Razor MX/SX platform.

Unlike the Ultimate and Extreme kits, the 6+7 system uses a full 420 drivetrain. Our Razor MX/SX Swingarm Extensions are mandatory because the larger motor requires additional clearance.

Required gearing is:

  • 10-inch rear wheel: 8T/47T 420 sprockets
  • 12-inch rear wheel: 8T/55T 420 sprockets

The 10-inch sprockets are included. The 12-inch sprocket setup is not included.

Choose this kit if you want maximum torque, heavy-duty drivetrain strength, and ETM RTR-style performance in your Razor chassis. Your brakes, suspension, wheel system, and chassis should be fully upgraded before installing it.

Razor Pro Spec Compatibility Warning

Our Pro Spec Extreme 14,000W Razor Kit is designed specifically for the newer Razor Dirt Rocket Pro Spec chassis.

It is not the correct direct-fit power kit for a conventional Razor MX650 or SX500.

7. Battery and Charging System

Your battery determines more than range. Voltage, current capability, battery-management-system limits, connectors, enclosure construction, and physical dimensions must all match your controller and chassis.

Our current Razor-compatible battery options include:

Use the battery specified on the selected power-kit page. Do not choose a battery based only on its voltage or whether it appears to fit inside the frame.

Before installation:

  • Verify that the battery fits your MX650 or SX500 tray.
  • Match the battery connector and leads.
  • Use the correct charger voltage.
  • Secure the battery against movement and impact.
  • Protect the battery and electronics from water.
  • Never bypass the battery-management system.
  • Inspect cables and connectors for heat after your first test rides.

Our supplied batteries and electronics are splash-resistant, not waterproof.

You can also read our published Battery Upgrades! article for more information about our focus on voltage, power, and safety.

Charger Options

Use only a charger that matches your battery’s voltage and connector. Available charging products include:

Confirm compatibility with your battery before connecting a charger.

8. Drivetrain and Gearing

Your motor, rear-wheel diameter, sprockets, and chain system must be planned together.

Ultimate Kit Gearing

Our Ultimate 5000W Razor Kit V3.0 includes our E&C Razor #35 HD Ultralight Sprocket and Chain Kit.

Recommended ratios are:

  • 10-inch rear wheel: approximately 8:1 to 6:1
  • 12-inch rear wheel: approximately 9.6:1 to 7.8:1
  • 14-inch rear wheel: approximately 11.52:1 to 9.36:1

We do not recommend a 14-inch rear wheel for this system.

Extreme Kit Gearing

The “ONE” Brushless Motor arrives with a #35 motor sprocket. A compatible #35 chain conversion is required.

Use our E&C Razor #35 HD Ultralight Sprocket and Chain Kit rather than attempting to retain the stock drivetrain.

6+7 Kit Gearing

Our 6+7 13kW Razor Upgrade Kit uses a substantially heavier 420 chain system:

  • 10-inch rear wheel: 8T/47T
  • 12-inch rear wheel: 8T/55T

Lower gearing generally improves acceleration, climbing ability, and motor-temperature control. Taller gearing may increase theoretical top speed but places additional load on the motor, controller, and battery.

Begin with our recommended ratio for your installed wheel diameter.

9. Controls, Display, Charging, and Accessories

Once your mechanical and power systems are complete, you can finish the build with controls and accessories.

Useful additions include:

Accessories designed for 12V operation require an appropriate DC-DC converter. Never connect a 12V headlight, USB charger, or lighting accessory directly to a 72V or 76V traction battery.

We recommend installing cosmetic and convenience accessories last so they do not complicate your essential chassis, brake, drivetrain, or power-system work.

Recommended Build Packages

Our Recommended All-Around MX650 Build

Our Recommended All-Around SX500 Build

Our Recommended Street/Supermoto Build

Our Recommended Maximum-Performance Build

Our Final Recommendation

For most MX650 and SX500 owners, we recommend starting with our Ultimate 5000W Razor Kit V3.0. It delivers a dramatic performance increase while retaining a straightforward, matched installation.

For an off-road build, pair it with our Razor Pit Bike Rear Wheel. Replacing the factory freewheel with a solid hub and direct bolt-on sprocket gives your upgraded drivetrain a stronger and more reliable foundation.

Our Extreme 11,000W Razor Kit and 6+7 13kW Razor Upgrade Kit belong in builds where braking, suspension, wheel strength, chassis stability, battery capability, and drivetrain durability have already been addressed.

At 11–13kW, those supporting components are not optional extras. They are part of the power upgrade.

Build your Razor as a complete system: brakes first, followed by wheels, suspension, chassis geometry, power, battery, and drivetrain. That process gives you a bike that does more than accelerate hard—it gives you a bike that can put the power down, maintain its balance, and stop consistently.

Related to:

General Knowledge Dirt Rocket MX500 / 650 / SX500 guide

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