Ultimate Razor Belt Drive Kit - Kr5v

MXMods Ultimate Belt Drive Kit — KR5V Motor

If you've spent any time on a Razor with a chain, you know the problems: chains stretch, rust, need constant lubrication, and the stock tensioner is garbage. A belt system eliminates all of that. Here's what changes when you go belt drive:

Maintenance: no more chain slop, constant lubrication, and broken links. just install and ride. with chain systems, lubrication is necessary, and gets messy.

Noise: Near-silent, sounds like a freakin' missile, no more metal on metal rattle, all you hear is pure, raw motor sound.

Power Curve: Arguably the best improvement over chain drive, the throttle feels smooth as butter, and drastically improves the smoothness of your bike, its hard to explain without feeling it, but especially with cheaper amazon/vevor controllers that feel jerky and delayed, this belt drive system is the best and cheapest upgrade to remove that issue. imagine going from a old truck to a tesla plaid.

This kit is for people running:

• Razor MX650, MX500, or SX500 dirt bike
• 3–4 inch extended swingarm
• KR5V motor

Upgrade your Razor with the ultimate belt drive kit, engineered for a quieter, smoother ride. Rated for 8000W with a 7:1 gear ratio, this is the most capable belt drive kit MXMods offers — built specifically for the higher power demands of the KR5V. Where the MY1020 kits use plastic pulleys and an HTD 5M belt, the Ultimate kit steps up to black anodized aluminum pulleys and a wider HTD 8M belt with larger teeth, giving you a dramatically stronger, more durable drivetrain that won't slip or wear out under high power. With a belt drive system, the riding experience becomes drastically smoother on takeoffs and at high speeds, especially with jerky controllers, making it the perfect upgrade for riders seeking a refined riding experience.

Specifications

What's in the Box

• Front motor pulley — 14T, black anodized aluminum (sized for KR5V shaft)
• Rear pulley — 98T, black anodized aluminum (mounts over your existing stock sprocket)
• HTD 8M timing belt (1128mm, pre-sized for 3–4" swingarm geometry)
• All necessary mounting hardware

Installation Overview

Installation takes 30–60 minutes with common hand tools. The rear pulley mounts directly over the stock sprocket on the freewheel hub. No frame cutting or welding required for the kit itself.

This kit is designed for riders who already have a 3–4 inch swingarm extension installed. The extended swingarm is required to achieve proper belt tension. It will NOT work on a stock swingarm.

Note: If your swingarm has a built-in belt tensioner, a separate motor-mounted tensioner is not required.

Freewheel Recommendation: We strongly recommend welding your freewheel before installing any belt drive. A welded freewheel eliminates the "clunk" on takeoff, provides smoother acceleration, and dramatically increases drivetrain longevity. The stock freewheel was not designed for the power levels most modded Razors push, and using it unwelded can lead to premature wear on your belt and pulleys. Setups without welded freewheels are NOT covered in the warranty.

Important: All products on MXMods are aftermarket and subject to our terms of use.