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Choosing the right 40-tooth rear sprocket can improve takeoff, balance torque, and help optimize fuel efficiency on popular mini bikes and go-karts. This guide focuses on five top 40T sprockets designed for Coleman, Baja, Massimo, TrailMaster, Predator, and similar mini-bike platforms. Each option offers distinct bore sizes, mounting patterns, and finishes to suit different engines and chain pitches. Use this overview to compare compatibility, installation, and durability before upgrading your ride’s gearing.

YOXUFA 40T Sprocket For Coleman Mini Bikes

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The YOXUFA 40T rear sprocket is built for 420 chain setups and fits a broad set of Coleman, Baja, TrailMaster, Massimo, and Axis models. With a 40 mm bore, it aligns cleanly with common mini-bike hubs and provides reliable torque transfer across 40-tooth gear ratios. Its compatibility list includes BT200X, CT200U, CT200U-EX, CT200U-EXR, MB165 & MB200, and MB200-series machines, making it a versatile upgrade for enthusiasts who own multiple platforms or plan to upgrade several bikes in a fleet. The design emphasizes durability and corrosion resistance through a black anodized finish.

In practice, upgrading to a 40T sprocket can help balance top-end speed with usable low-end torque when paired with a consistent front chainring. The 420 chain compatibility ensures a robust connection under acceleration, while the precision-machined alloy construction resists wear from rough terrains. Installation is straightforward for users familiar with basic sprocket swaps, and the 40T count provides a noticeable step up in performance without requiring other drivetrain changes. This model is a reliable all-rounder for daily riders and weekend enthusiasts alike.

CILOYU High Speed 420 Rear Sprocket 40T

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The CILOYU 40T high-speed rear sprocket is designed for 420-chain minibikes with a 37 mm center bore and six mounting holes, delivering a robust mounting footprint and a tighter fit on compatible hubs. This combination supports Coleman CT100U/CC100X and Baja Doodle Bug DB30 family machines, along with Motovox MBX10/MBX11 and Monster Moto variants. The 40-tooth gear is positioned to improve acceleration while maintaining stable power delivery, especially on bikes with smaller engines in the 80cc–105cc range. The six-bolt layout helps distribute load evenly, reducing wear on mounting points over time.

Engineered for performance, this sprocket emphasizes precision machining and a durable alloy composition. A common feature across CILOYU’s mid-range sprockets is reliability in real-world conditions—whether carving a trail, racing on a track, or simply commuting around a neighborhood. While the bore is smaller than some 40T options, the 37 mm size works well with a variety of hubs and spacers. Riders seeking a balance of speed, torque, and ease of install will find this a solid upgrade.

YZMLOL 40T Sprocket For Coleman Mini Bikes

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The YZMLOL 40T rear sprocket is built for 420-chain minibikes and carries a 40 mm center bore with six mounting holes, ensuring a secure, stable fit on compatible hubs. It is advertised as compatible with Coleman CT200U/CT200U-EX/BT200X, MB165/MB200, Hensim MB200, and TrailMaster MB200, as well as Massimo MB200. The precision-machined metal alloy construction and black anodized finish contribute to long-lasting wear resistance and corrosion protection, making this sprocket a durable choice for riders tackling varied terrain. The 40T count supports smooth power delivery and fuel efficiency improvements when paired with the correct front sprocket.

Performance-wise, upgrading to a 40T sprocket with a 420 chain typically yields a slightly higher top-end and better cruising efficiency, particularly on mid-sized engines around 196cc–212cc. While the exact bore and hole spacing are optimized for certain models, the design aims to maximize stability during aggressive throttle use. This makes it a practical option for riders who value longevity and consistent performance across multiple bikes in their stable.

Stylemafia 40/41/420 Chain Sprocket 40T

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The Stylemafia 40T sprocket is designed to fit Coleman BT200X, CT200U, CT200U-EX, and CT200U-EXR models, along with MB165/MB200, TrailMaster MB200, and Massimo MB200 systems. It features 6 mounting holes and a 1-9/16″ center bore (40 mm) with an overall diameter of 6-1/2″ (165 mm). The brand emphasizes a precision-machined metal alloy build with a black anodized finish for rust and corrosion protection. This makes the sprocket suitable for riders who demand both durability and straightforward installation, even in harsher riding conditions.

From a performance perspective, this 40T option is well-suited for riders seeking a smoother, more controlled ride with modest gains in top-end speed. The 420-chain compatibility ensures strong engagement with the chain, minimizing slip during abrupt throttle changes. For those upgrading an MB200-series bike or a Coleman CT200U family model, this sprocket offers a balanced blend of durability and efficiency without requiring extensive drivetrain changes.

XIKOBY 40-Tooth Rear Sprocket For Mini Bikes

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The XIKOBY 40-tooth rear sprocket focuses on compatibility with Predator 97cc/98cc/100cc engines, plus Coleman CT100U/CC100X RB100, and MBX10/MBX11 bikes. It features a 40-tooth design and a 12-hole mounting pattern, offering flexibility for various hub spacings and alignment setups. While the listing does not clearly specify bore size, the design emphasizes robust steel construction and reliable engagement with 420 or compatible chain pitches. The 12-hole arrangement provides multiple mounting options, helping ensure a secure fit on bikes with older or non-standard hubs.

As a gearing upgrade, this sprocket aims to improve chain engagement and reduce wear on the tooth peaks under heavy throttle. The 40T count supports a balanced performance profile—adequate acceleration paired with manageable top speed when used with the right front sprocket. It’s a practical choice for riders who value durability and mounting versatility across a diverse range of minibikes and go-karts.

Buying Guide

Key Compatibility Factors

• Confirm chain pitch compatibility. Most 40T upgrades assume a 420 chain; some models may handle 41 or 42 pitch as well. Mixing chain pitch can cause poor engagement or accelerated wear.
• Check model compatibility. Review the compatibility notes for CT, MB, TrailMaster, Massimo, Baja, and Predator families to avoid misfits.
• Match bore size to your hub. Common bores are 37 mm and 40 mm; ensure your hub’s center bore matches or can be accommodated with spacers if needed.

Size, Bore, And Mounting Pattern

• 40T is a common upgrade for boosting top speed while preserving some torque. If you need more torque, consider staying with the front sprocket while using a larger back gear cautiously.
• Six-bolt (or more) mounting patterns distribute load and reduce warping. Verify the number of mounting holes and their spacing (often around 80 mm center-to-center).
• Be mindful of overall diameter, especially on bikes with tight chain routing. A 6-1/2″ diameter is typical for many 40T options.

Material And Finish

• Black anodized aluminum or alloy sprockets offer corrosion resistance and better wear performance in dusty or wet environments.
• Durability matters on mid-range engines (80cc–212cc). A high-quality alloy will tolerate off-road use without excessive wear.

Performance Trade-Offs

• Smaller rear sprockets generally improve top speed and fuel economy but reduce off-the-line torque. Pair with an appropriate front sprocket to maintain usable acceleration.
• For hill climbs or heavy throttle use, ensure the front sprocket size is adjusted to keep a usable torque curve.

Installation Tips

• Clean mounting surfaces and verify alignment before torquing bolts. Misalignment can cause premature wear on the sprocket and chain.
• Use the correct hardware and spacer if needed. Some models require longer bolts or washers to clear the chain line.
• Check chain tension after installation and re-tension after a few ride cycles as the chain seats in.