CILOYU Mini Bike Sprocket 40T 40mm Bore Kit with 420 Chain — Complete Replacement for CT100U/CT200U

CILOYU Mini Bike Sprocket 40T is a heavy-duty 40-tooth 420-chain sprocket kit built to replace or upgrade drivetrains on CT100U/CT200U-style mini bikes and similar 200–212cc machines.

This complete sprocket and chain kit supplies a larger-diameter 40-tooth driven sprocket plus a matching 420 chain, sprocket key, master links, mounting hardware and a chain breaker — everything needed to install on a range of small off-road bikes and go-karts. The design adds mounting hole options and a bigger center bore to fit engines and hubs commonly found on Coleman, Baja, Hensim, Massimo and other mini bike platforms, improving torque delivery and reducing wear compared with smaller 420 sprockets.

How will this 40T sprocket change my bike’s performance?

Moving to a 40-tooth driven sprocket typically increases low-end acceleration and climbing power by giving the engine more mechanical advantage at the rear wheel. Riders who want stronger pull from a stop or when climbing trails will notice improved torque, although top speed may be reduced if gear ratios are made shorter.

• Higher torque and stronger initial acceleration
• Smoother power transfer with precision-machined teeth
• Better chain life due to improved tooth engagement
• Ideal for off-road and uneven terrain where low-speed control matters

Which mini bikes and engines is this kit compatible with?

The kit is intentionally universal across many small-engine mini bikes and go-karts that use 420 chain sizes and common mounting patterns. It suits a broad list of models from manufacturers like Coleman, Baja, Hensim, Massimo, TrailMaster and others, but compatibility depends on the bolt-circle and center-bore dimensions of your hub or engine sprocket area.

• Fits many 196–212cc and similar small engines with 420 chain drives
• Works on Coleman CT100U, CT200U and similar models with adapter changes
• Four- and six-hole mounting patterns match multiple hub types
• Center bore 40 mm to accommodate larger engine output shafts

What hardware and extra parts are included for installation?

This kit is packaged to be installation-ready: you get the 40T driven sprocket plus a smaller 10T counter sprocket, two lengths of 420 chain, a chain breaker, master links, mounting screws and nuts, and a 3/16" keyway. The included items let you adapt the kit to different setups without hunting for add-ons.

• 40T 420 driven sprocket and 10T counter sprocket
• 90-link and 42-link 420 chains with five master links
• Ten screws, ten nuts, 3/16" key and a chain breaker tool
• Mounting hole patterns: 49 mm and 80 mm bolt circles

How do I know the sprocket will physically fit my setup?

Measure your current sprocket’s bolt-circle diameter and center bore before ordering. This CILOYU sprocket offers two bolt-circle sizes (49 mm and 80 mm) plus a 40 mm center hole so it matches many hubs; the six-hole option fits larger-engine conversions while the outer four holes suit standard mini-bike hubs.

• Center bore: 40 mm (1.57")
• Six-hole bolt circle: 49 mm center-to-center
• Four-hole bolt circle: 80 mm center-to-center
• Use included screws and nuts sized for typical mini-bike hubs

Who is this for: riders and tinkerers upgrading mini-bike drivetrains, small-engine mechanics, and DIY go-kart builders who need a robust 420-chain 40-tooth sprocket kit with multiple mounting options. If you run a Coleman, Baja, Hensim, Massimo, TrailMaster or similar mini bike and want stronger low-end pull, longer chain life, and a kit that includes installation hardware, this CILOYU set is designed for that use. Always verify bolt-circle and center-bore measurements for a correct fit before installation.