CILOYU 40T Rear Sprocket and 140-Link #35 Chain for CT100U, 37mm Bore — Alloy, 6-Hole Fit

The CILOYU 40-tooth rear sprocket paired with a 140-link #35 drive chain is a drop-in powertrain upgrade for CT100U-style mini bikes and many small go-karts.

This kit combines a machined alloy 40T sprocket (37 mm center bore) and a full 140-link #35 chain to restore or improve drivetrain performance on compact bikes and kart frames. It’s designed to match popular small-engine platforms such as Predator 97–100cc, Coleman CT100U series, and several Baja, Motovox, Monster Moto, and similar models. The package focuses on straightforward fitment with six mounting holes and optimized hole spacing so most installations require no drilling or alteration.

Will this sprocket and chain fit my CT100U or similar mini bike?

Yes — the sprocket and chain are sized for the common CT100U mounting pattern and #35 chain systems. Confirm your bike’s measurements against the supplied dimensions before ordering to ensure compatibility.

• Center bore diameter: 37 mm (1.45"), matching many 37 mm hubs
• Mounting hole spacing: 49 mm (1.92") and hole diameter: 37 mm (1.46")
• Tooth count: 40T, chain size: #35 with 140 links included

How durable and reliable is the CILOYU sprocket and chain set?

The sprocket is machined from a metal alloy with precision-cut teeth to reduce wear and prevent chain derailment. The #35 chain included is built for repetitive loads typical of mini bikes and light go-karts.

• Alloy construction for corrosion and impact resistance
• Precision tooth profile to reduce skipping and premature wear
• 140-link length allows for a range of chainline adjustments without immediate shortening

What performance changes can I expect after installing this 40T sprocket?

Swapping to a 40-tooth rear sprocket typically raises the effective gearing compared with smaller rear sprockets, which can increase top speed and improve cruising efficiency when paired with the stock front sprocket. Real-world gains depend on engine, tire size, and vehicle weight.

• Higher gear ratio potential for increased top-end speed
• May improve fuel efficiency at steady speeds when engine RPMs are optimized
• Maintains compatible kart front sprocket—no front change required for many setups

How easy is installation and what mounting features help fit different frames?

CILOYU designed the sprocket with six mounting holes and improved hole spacing to reduce the need for frame modification. Many users will find it a direct replacement; a basic toolkit and chain-breaking tool are typically sufficient for installation.

• Six-hole pattern increases compatibility across mini bike and go-kart hubs
• Optimized hole spacing reduces need for drilling or adapters
• Includes 140-link chain so you can size and join the chain on-site

Who this is for: This sprocket-and-chain kit is intended for owners and mechanics of CT100U-style mini bikes and similar small-frame karts who want a durable replacement or a modest gearing change without custom fabrication. It’s suitable for riders using Predator 97–100cc engines, Coleman mini bikes (CT100U, CK100, SK100, CC100X), select Baja and Motovox models, and compatible 80–105cc Monster Moto bikes. If you need a ready-to-fit rear sprocket with a full-length #35 chain and clear mounting specs, this set delivers a cost-effective option for maintenance and mild performance tuning.