CILOYU 40-Tooth 420 Sprocket for Mini Bike — 40mm Bore, Dual Bolt Circles & Hardware Kit

The CILOYU 40-tooth 420 sprocket with a 40mm center bore is a direct-fit replacement designed to upgrade mini bike drivetrains for models using 420 chain.

This replacement sprocket is built for riders and mechanics who need a robust, adaptable hub gear for mini bikes and small go-karts that accept a 420-size chain. Crafted to accept multiple bolt patterns and supplied with installation hardware and master links, the sprocket aims to make swaps faster and reduce compatibility guesswork across a range of common small-engine machines.

Which vehicles will this sprocket fit?

This sprocket supports many popular mini bike and go-kart platforms that run a 420 chain and a 40mm center bore. It includes two bolt-circle options to match either smaller or larger mounting patterns commonly found on engines and hubs.

• Compatible with engines like Predator 212cc and similar 6.5hp variants.
• Fits models such as Coleman CT200U, CT100U, CC100X, Baja/TrailMaster variants, and several Hensim and Massimo mini bikes.
• Two bolt circles: 49 mm (6-hole pattern) and 80 mm (4-hole pattern) to suit different hubs.
• Includes 40 mm center bore for direct installation on matching shafts or with minor adapter hardware.

How does the 40-tooth design affect performance?

A larger sprocket tooth count changes final drive ratio, which typically alters acceleration feel and torque delivered at the rear wheel. This 40T unit is intended to offer stronger low-end pull and improved climbing response compared with smaller driven sprockets, while remaining compatible with standard 420 chain pitch.

• 40 teeth increase rear-wheel torque relative to smaller sprockets.
• Precision-machined teeth promote smoother chain engagement and less chatter.
• Suitable for mixed terrain riding where low-speed control is desired.
• Works with standard 420 chain supplied or aftermarket chains rated for mini bikes.

What hardware and measurements are included for installation?

The sprocket ships as a kit with fasteners and master links so you have the basic parts to fit it without sourcing extras. Exact mounting diameters and the bore size are provided so installers can verify fit before beginning work.

• Center bore diameter: 40 mm (1.57"), for direct-mount shafts or with standard bushings.
• 6-hole bolt circle: 49 mm (center-to-center) for certain mini bike hubs.
• 4-hole bolt circle: 80 mm (center-to-center) for larger hub/engine patterns.
• Kit contents: one 40T 420 sprocket, five 420 master links, ten screws and ten nuts for mounting.

How do I know this will replace my current sprocket?

Confirm the driven sprocket’s current chain size, center bore, and bolt circle measurements before purchasing. The dual bolt-circle design increases the chance of compatibility with many popular mini bike hubs and engines, but measuring prevents surprises.

• Measure your existing sprocket bore and bolt pattern to match 40 mm, 49 mm, or 80 mm specs.
• Verify your bike uses a 420 chain (check link pitch and width).
• If in doubt, compare mounting hole count and spacing to this sprocket’s two patterns.

Who is this for: This CILOYU 40T 420 sprocket is intended for mini bike owners, small-engine hobbyists, and repair shops needing a durable replacement or an upgrade to alter drive ratios. It is best for riders using machines that accept 420 chain and require a 40mm bore or the two supported bolt-circle patterns; hobbyists who want a ready-to-install kit will appreciate the included master links and fasteners.