JMCHstore 40T High-Speed Rear Sprocket for Mini Bikes - 6-Hole, #40/41/420 Chain, Gold Zinc Finish

This heavy-duty sprocket replaces worn or stock rear gears on a range of small-frame bikes including Coleman CT100U, CC100X, Baja Doodle Bug DB30, Mega Moto MMB80/105 and several 105cc mini bike models. Built from high-strength steel with a gold zinc corrosion-resistant finish, the part is intended for #40/41/420 chain systems and for engines 212cc and larger where improved power transfer and high-speed capability matter. Check fitment dimensions carefully—this sprocket uses a six-bolt pattern and specific hole spacing that does not match most go-karts.

Will this sprocket fit my mini bike or pit bike?

Compatibility depends on your bike's bolt pattern and chain size. This sprocket is made for #40/41/420 chain and a six-hole mounting layout with a 49mm bolt circle; it fits many Coleman, Baja, Mega Moto, Motovox and similar mini bikes but not go-karts with different mounting patterns.

• Chain size: #40/41/420 compatible
• Teeth: 40-tooth design for higher top speed
• Bolt circle (center-to-center): 49mm / center hole: 37mm
• Mounting holes: 6 holes, 6.5mm diameter each

How does it change performance on flat roads or racing setups?

The 40-tooth profile is optimized for higher-velocity runs by reducing the final drive ratio compared with smaller sprockets. Riders can expect improved top-end speed while the precision-cut teeth help maintain consistent chain engagement under load, minimizing slip on long, flat sections.

• Designed for flat-road and high-speed conditions
• Precision-cut teeth reduce chain wear and vibration
• Durable steel construction resists deformation at high RPM

Is this sprocket durable and weather-resistant?

Yes—manufactured from premium high-strength steel and finished with a gold zinc plating to resist rust and corrosion. That surface treatment protects the sprocket in wet or salty conditions and extends useful life when maintained with regular cleaning and lubrication.

• High-strength steel resists bending and tooth wear
• Gold zinc plating protects against rust and corrosion
• Precision engineering reduces drivetrain stress and extends life

What should I know about installation and engine compatibility?

Installation requires matching the six-hole bolt pattern and center hole diameter to your wheel hub. It is designed to support upgraded 212cc and larger engines without chain slippage, but proper chain tensioning and alignment are still essential for safe, reliable operation.

• Center hole diameter: 37mm (1.46 inch)
• Overall diameter: 165mm (6.49 inch)
• Fits many 105cc–212cc upgraded engine applications
• Not compatible with most go-karts due to different mounting patterns

Who is this for? The JMCHstore 40T sprocket is aimed at riders and mechanics upgrading or replacing rear sprockets on mini bikes and small pit bikes who want higher top speed, reliable power transfer, and corrosion resistance. If you run a Coleman CT100U, Baja DB30, Mega Moto MMB80/MMB105, Motovox MBX10 or similar models and have a #40/41/420 chain with a six-bolt wheel hub, this sprocket is engineered to meet those needs. Verify your bike’s bolt circle, center hole, and chain size before ordering to ensure a correct fit and safe installation.