From Backyard Cruiser to Dirt-Slinging Beast: Upgrading the Razor MX650
If you've ever ridden a Razor MX650 and thought, "this thing needs more juice," you're not alone. The MX650 is one of the most popular entry-level electric dirt bikes on the market — and also one of the most popular platforms for serious performance upgrades. With the right trio of components — the Kunray KR5V Motor, the Fardriver ND72450 Controller, and an Amorge 72V Lithium Battery — you can transform this modest ride into something that'll genuinely turn heads on the trail.
The Stock Razor MX650: Good Bones, Modest Power
The Razor MX650 Dirt Rocket is powered by a 650-watt electric motor that can reach speeds of up to 17 miles per hour, with a run time of up to 40 minutes on a single charge. It features dual suspension, hand-operated disc brakes, a steel frame with authentic dirt bike geometry, and a 36V sealed lead-acid battery system.
For younger riders or beginners, this setup is genuinely capable. The problem? The battery takes around 12 hours to fully charge, and the relatively short battery life and long charging time may be a drawback for some riders. For anyone over 150 lbs who wants to ride actual terrain — hills, jumps, dirt tracks — the stock motor and lead-acid batteries simply can't keep up.
That's where the upgrade path begins.
The Upgrade Components
Kunray KR5V Motor — The Heart of the Build
The Kunray KR5V V2 is a next-generation 72V 5000W high-performance brushless motor engineered for dirt bikes, e-motorcycles, go-karts, and Razor MX/SX series vehicles. It mounts directly into the Razor MX650, MX500, SX500, Indian650, and RSF650 chassis without modification. Check it out at ECONIC CYCLES
The jump from 650W to 5,000W rated power (with a peak of 10kW and peak torque of 35 N·m) is staggering. The motor features a pure copper core with maximum efficiency of 90%, and is equipped with a heatsink and air cooling system designed to handle high temperatures and maintain optimal performance. With a 6.0 gear ratio, riders are hitting 60 mph at full charge on 72V — though results can vary depending on rider weight, wheel size, and terrain.
As a brushless (BLDC) motor, it provides higher efficiency, reduced maintenance, lower heat generation, and a longer service life compared to brushed motors.
Fardriver ND72450 Controller — The Brain of the System
A high-power motor is only as good as the controller managing it. The FarDriver 72450 is a high-performance sine wave controller that supports 48V to 72V systems and offers a peak phase current of 450A, ensuring smooth and efficient power delivery. It features wireless programming via the FarDriver app, compatible with both iOS and Android, allowing for easy customization. Check it out at ECONIC CYCLES
Built-in protections include locked-rotor protection, over-current protection, overload protection, over-temperature protection, speed protection, over-voltage protection, and under-voltage protection. Whether climbing a steep hill, cruising a flat highway, or navigating city traffic, the controller's intelligent management of phase and bus current allows the bike to adapt and perform at its best.
The controller carries an IP67 waterproof rating, making it trail-ready in real-world conditions.
Amorge 72V Lithium Battery — The Fuel Behind the Fire
This is where the upgrade gets truly transformative. Ditching the stock 36V sealed lead-acid pack for an Amorge 72V lithium battery — available in configurations like the 20S5P 72V 20Ah pack with ANT Bluetooth BMS — doubles your voltage and dramatically cuts weight. Amorge has been manufacturing lithium battery packs since 2013, with over 12 years of manufacturing experience. Their lineup scales from 20Ah commuter builds all the way up to 80Ah high-discharge packs capable of 400A continuous output. For an MX650 upgrade, a 20–30Ah pack in the 72V range hits a sweet spot between range, weight, and budget. Photo Courtesy of ECONIC CYCLES
Pros of the Upgrade
Explosive Power Increase — Going from 650W to 5,000W (with 10kW peak) is not a subtle improvement. The torque alone will have the front wheel lifting off if you're not careful.
Brushless Efficiency — The KR5V's brushless design means less heat, less wear, and more ride time between maintenance intervals compared to the stock brushed motor.
Precise, Programmable Control — The Fardriver's sine-wave drive and Bluetooth app let you dial in throttle curves, speed modes, and braking behavior to your exact riding style.
Massive Range Improvement — Swapping the lead-acid pack for a lithium Amorge battery not only reduces weight by several pounds, it also delivers more usable capacity, faster charging, and a much flatter discharge curve — meaning power stays consistent until the battery is nearly empty.
Drop-In Compatibility — The KR5V was designed with the MX650 frame in mind, meaning you're not hacking mounts or fabricating brackets. It's a legitimate bolt-on upgrade.
Cons of the Upgrade
Cost — The combined cost of a quality motor, Fardriver controller, and Amorge 72V lithium pack can easily run $500–$900+ depending on the battery capacity you choose. That's potentially more than the bike itself cost new.
It's No Longer a Beginner's Bike — At 50 mph plus potential on a platform that originally topped out at 17 mph, this is a genuinely dangerous machine if the rider isn't experienced. The stock brakes, suspension, and tires were not designed for these speeds.
Wiring Knowledge Required — While the motor mounts without modification, the full electrical swap — controller wiring, BMS integration, throttle mapping — requires a solid understanding of EV electronics. This is not a beginner's weekend project.
Warranty Void — Any modification immediately voids the Razor warranty. The bike also transitions out of "toy" territory legally and may require registration, insurance, or be restricted from certain riding areas depending on your state.
Frame & Suspension Limits — The MX650's steel frame and entry-level suspension were engineered for a 650W motor. Sustained high-power riding may stress the chassis and components beyond their design intent. Upgrading brakes should be considered a requirement, not optional.
Final Verdict
The Razor MX650 is one of the best bang-for-buck upgrade platforms in the e-bike world precisely because of how purpose-built the Kunray/Fardriver/Amorge combination is for it. If you're a mechanically inclined adult rider who wants a capable electric dirt bike without paying Sur-Ron money, this build path is worth serious consideration. Just go in with eyes open — the power is real, the responsibility is greater, and the upgrade demands respect for both the electrical system and the machine you're building.
Ride smart. Upgrade smarter.