RZEOZU 50-Tooth Rear Sprocket for 420 Chain — 6-Bolt Mini Bike Replacement, Hardened Steel with Hardware

RZEOZU's 50-tooth rear sprocket for 420 chains is a steel replacement designed to give mini bikes smoother power transfer and reliable fitment for a wide range of 6" wheel, 6-bolt mini bike models.

This replacement sprocket is built for riders who upgrade to a 420 chain or run larger engines (212cc and up) and need a durable, accurately machined rear cog. It includes the hardware and master links required for installation and is sized to match common mini bike mounting patterns. Read on for fit, installation details, and what to expect from performance and durability.

Will this sprocket fit my mini bike?

Check three critical measurements before buying: bolt circle diameter, center bore, and number of mounting holes. This RZEOZU sprocket features a 6-bolt pattern with a bolt circle of 49 mm (1.93") and a center hole of 37 mm (1.46"), so compare those to your hub.

• Bolt holes: 6
• Bolt circle diameter: 49 mm (1.93")
• Center bore: 37 mm (1.46")
• Overall diameter: 205.5 mm (8.09")

How does the 50-tooth design affect riding and gearing?

A 50-tooth rear sprocket increases mechanical advantage vs. smaller cogs, which can help with acceleration and low-end pulling power when paired with the correct front sprocket. The tooth count is precision-cut to provide smoother chain engagement and to reduce uneven wear over time.

• Tooth count: 50 — boosts torque at the wheel
• Precision-cut teeth for consistent engagement
• Works best with 420 chain setups and larger-displacement engines

What materials and accessories come with the sprocket?

The sprocket is made from hardened steel to balance strength and resistance to corrosion while remaining weight-conscious. RZEOZU packages the sprocket with mounting hardware and chain links so you have what’s needed to install it without an extra trip to the parts store.

• Material: hardened steel for durability
• Includes: 5 master links, 6 bolts, 6 nuts, and a wrench
• Pre-drilled 6-hole pattern for standard mini bike hubs

How difficult is installation and what should I prepare?

Installation is straightforward for anyone comfortable with basic mini bike maintenance and chain work. You'll need to verify the sprocket centers and torque the supplied fasteners to the manufacturer's specifications, then size and rivet the master link to the chain length you require.

• Tools recommended: socket set, torque wrench, chain breaker/plier
• Adjust chain tension after mounting
• Check alignment and fastener torque on first ride

Who is this for: Riders upgrading or repairing mini bikes such as the Coleman CT100U, CC100X, RB100, Baja DB30, Mega Moto MMB80/MMB105, Motovox MBX10/MBX11 and similar machines that use a 6" rim with a small 6-bolt pattern and a 420 chain. It’s aimed at owners converting to 420 chain sizes or installing larger engines (212cc+), DIY mechanics who want a complete replacement kit, and anyone seeking a long-lasting steel rear sprocket to restore drivetrain performance.