The Complete Razor MX500/SX500 Upgrade Guide: Everything You Need to Know

Introduction: Why Upgrade Your Razor Electric Dirt Bike?

If you've been riding a stock Razor MX500, MX650, SX500, or SX650, you already know these bikes punch above their weight class. But if you're ready to take your build to the next level — more speed, better handling, stronger brakes, and longer range — aftermarket upgrades are the answer.

At ThatRazorKidd LLC, we specialize in precision-engineered, durable parts built specifically for the Razor platform. This guide walks you through every major upgrade category, from motors to batteries, so you can build the Razor of your dreams with confidence.

1. Motor Upgrades: Stock vs. Aftermarket

The motor is the heart of your build. Stock Razor motors are fine for casual riding, but they hit a ceiling fast — especially if you're running higher voltage or pushing the bike hard on trails or tracks.

Sotion GTS11 – 7Kw Motor
The Sotion GTS11 7Kw Motor is one of the most popular upgrades for serious Razor builders. With 7 kilowatts of output, it delivers a massive power increase over stock and pairs perfectly with a 72V battery system. It's a direct-fit upgrade for MX500, MX650, SX500, and SX650 frames when paired with the right controller.

Kunray KR5V V2 – 72V 5000W Motor
The Kunray KR5V V2 72V 5000W BLDC Motor is another top-tier option for Razor upgrades. Running at 72V with 5000W of power, the KR5V V2 is a proven performer with a strong community following. It's a great choice for riders who want a reliable, well-documented upgrade path.

Pro tip: When upgrading your motor, always upgrade your controller at the same time. A high-powered motor paired with a stock controller is a recipe for a fried board.

2. Controller Upgrades: FarDriver Mounts and Throttle Systems

A quality controller is what unlocks the full potential of your motor upgrade. FarDriver controllers are the gold standard in the Razor community for their programmability, reliability, and power handling.

FarDriver Mounts
Our 3D Printed FarDriver Mounts for ND72300, ND72450 & ND72680 are precision-designed to fit FarDriver controllers cleanly into Razor frames. No fabrication, no guesswork — just bolt them in and go.

Throttle Systems
Pairing the right throttle with your FarDriver controller makes a huge difference in ride feel. We carry a few great options:

• Domino Throttle Kit with 3 Speed Switch, Volt Meter & Pro-Taper Grips — the all-in-one premium setup for FarDriver builds. Includes a volt meter and 3-speed switch so you can monitor your battery and dial in your power delivery on the fly.
• Cable Throttle Adapter for FarDriver Controllers — a clean solution for riders who want to run a cable-pull throttle with their FarDriver setup.
• 3 Speed Switch — add selectable power modes to your existing throttle setup.

3. Suspension Upgrades: Bolt-On Kits for MX/SX Frames

Stock Razor suspension is one of the first things riders notice when they start pushing the bike harder. The forks are stiff, the travel is limited, and at higher speeds it gets sketchy fast. A proper suspension upgrade transforms the ride quality completely.

Razor MX/SX/RSF Fork Fully Bolt-On Suspension Upgrade Kit
The Razor MX/SX/RSF Fork Fully Bolt-On Suspension Upgrade Kit is exactly what it sounds like — a complete front suspension upgrade that bolts directly onto your existing Razor frame. No welding, no custom fabrication. This kit dramatically improves front-end feel, bump absorption, and overall control at speed.

Ride or Die Premium Fully Bolt-On Suspension Upgrade Kit
For riders who want the best of the best, the Ride or Die Premium Fully Bolt-On Suspension Upgrade Kit steps things up with premium components for the most demanding builds.

Pair either suspension kit with the Generic Bolt-On Rear Swing Arm Extensions to improve rear geometry and give your build a more aggressive, planted stance.

4. Brake Upgrades: Hydraulic Brake Kits and Rotors

More power means you need more stopping force. Stock Razor brakes are cable-actuated and simply aren't up to the task once you've upgraded your motor and battery. Hydraulic brakes are a must-have upgrade for any serious build.

We offer a full range of hydraulic brake options:

• Front and Rear Hydraulic Brake Kit — the complete package for riders who want to upgrade both ends at once. Best value if you're doing a full build.
• Front Hydraulic Brake Kit — upgrade the front brake independently for improved stopping power where it matters most.
• Rear Hydraulic Brake Kit — upgrade the rear brake for better modulation and control under hard deceleration.

Hydraulic brakes offer dramatically better feel, more consistent performance, and require less hand force than cable brakes — especially important when you're hauling at higher speeds.

5. Drivetrain Upgrades: Sprockets, Chains, and Gear Ratios

Dialing in your gear ratio is one of the most underrated tuning moves you can make. Changing your sprocket tooth count lets you trade top speed for acceleration (or vice versa) without touching your motor or controller.

We carry motor sprockets and rear sprockets to help you find the perfect ratio for your riding style:

• 12t and 13t #35 Motor Sprocket for Sotion FW11 & GTS11 — fine-tune your Sotion motor's power delivery with the right front sprocket.
• T8F Motor Sprocket for MY1020 & Early KR5V Motors — compatible with early KR5V builds.
• KR5V #35 11t Sprocket — the go-to front sprocket for KR5V motor builds.
• #35 Sprocket 64 Tooth — a popular rear sprocket choice for a balanced speed/torque ratio.
• #35 Sprocket 69 Tooth — more teeth = more torque and acceleration off the line.

General rule: A larger rear sprocket gives you more low-end torque and acceleration. A smaller rear sprocket (or larger front sprocket) gives you higher top speed. Most trail and track riders find a sweet spot somewhere in the middle.

6. Battery Upgrades: 72V Options for Maximum Performance

Upgrading to a 72V lithium battery is the single biggest performance unlock for your Razor build. More voltage means more speed, more torque, and more range — and it's what makes high-powered motors like the GTS11 and KR5V really come alive.

We carry a full lineup of 72V batteries to match your build's power demands:

• 72V 32AH 200AMP Battery for Razor MX500, MX650 & PROSPEC — a great all-around choice for MX-platform builds. Plenty of capacity for extended sessions.
• 72V 32AH 200AMP SX500 Battery — optimized for the SX500 platform.
• 72V 40AH 300A Razor SX500 Battery — maximum capacity for the most demanding SX500 builds. Ideal for riders who want the longest possible range and the headroom to run high-draw motors at full power.
• 72V 24AH 130AMP Battery — a lighter, more compact option for builds where weight savings matter.

Important: Always match your battery's continuous amp rating to your controller and motor's peak draw. Running a battery that's undersized for your setup will cause voltage sag and can shorten battery life.

Conclusion: How to Choose the Right Upgrades for Your Build

The best upgrade path depends on your goals, your budget, and how you ride. Here's a quick framework to help you prioritize:

• Just want more speed? Start with a 72V battery upgrade and a matching controller. It's the highest-impact change you can make to a stock bike.
• Building a trail or track machine? Motor + controller + suspension + hydraulic brakes is the full package. Do them together for the best results.
• Tuning an existing build? Dial in your gear ratio with sprocket swaps and make sure your battery amp rating matches your system's demands.
• Full send build? GTS11 or KR5V motor, FarDriver controller with Domino throttle kit, bolt-on suspension, hydraulic brakes front and rear, and a 72V 40AH battery. That's the recipe.

Have questions about which parts are right for your specific build? Reach out — we're riders too, and we're happy to help you spec out the perfect setup. Browse our full catalog at ThatRazorKidd.shop.