CILOYU 420 High-Speed 40T Minibike Sprocket — 37mm Bore, 10T Counter & Installation Kit

CILOYU 420 high-speed 40-tooth sprocket is a replacement and upgrade for minibikes with 212cc (and larger) engines, offering a 37mm center bore and hardware kit for straightforward installation.

If you’re rebuilding or tuning a minibike such as a Coleman CT100U, Baja Doodle Bug DB30, or similar models with 212cc engines, this sprocket provides a higher-speed gearing option built for durability and smooth chain engagement. The package includes the 40T sprocket plus a 10T counter sprocket, new 420 master link, mounting hardware, wrench and keyway so you can fit, test, and ride without sourcing additional parts.

How will this sprocket affect my minibike's performance?

Switching to the 40-tooth 420 sprocket adjusts the final drive ratio to favor higher top speed and stronger acceleration on larger-displacement minibikes. It’s engineered to work with a 420 chain, so power transfer is steady and efficient when matched to compatible engines and rear-wheel sizes.

• Higher top-end speed potential when paired with a 212cc or larger engine.
• Smoother torque delivery through precision-cut teeth.
• Comes with a 10T counter sprocket to complete the gearing change.

Will this sprocket fit my minibike and what are the exact measurements?

The sprocket is designed for many common minibike models but requires matching measurements to ensure compatibility. Key dimensions are provided so you can confirm fit before installation and avoid models that use different sprocket standards.

• Teeth: 40T; overall diameter: 6.50" (165 mm).
• Mounting pattern: 6 holes; bolt circle: 1.93" (49 mm) center-to-center.
• Center bore: 1.46" (37 mm) — not compatible with 200-series minibikes like CT200U.

What comes in the box and what tools are included?

The CILOYU kit includes the main sprocket plus the essential small parts to install and secure it to your minibike. Inclusion of the master link, counter sprocket and installation tools minimizes extra purchases and gets your drivetrain reassembled quickly.

• 1 x 420 chain 40T sprocket and 1 x 420 sprocket 10T.
• 5 x 420 master links, 6 screws, 6 nuts, 1 wrench and 1 3/16" keyway.
• Hardware designed to match the sprocket’s six-hole mounting pattern.

Who this sprocket is for: This CILOYU 40T 420 sprocket is aimed at DIY minibike owners, hobby mechanics and small-engine tinkerers upgrading Coleman CT100U, CC100X, RB100, B100, Baja Doodle Bug DB30, Monster Mega Moto MMB80/MMB105, Motovox MBX10 and similar models that accept a 420 chain and 37mm bore. It’s a good fit if you want a straightforward high-speed gearing change and a full hardware kit, but confirm the 37mm center hole and 6-hole pattern match your bike before ordering. Avoid this part for 200-series minibikes (e.g., CT200U), which use different dimensions.