Driven Racing 428 Rear Sprocket for Honda Grom, Monkey 125

Performance Gearing: Driven Racing 428 EVO TECH Rear Sprocket

Precision-engineered in the USA, the Driven Racing EVO TECH Rear Sprocket is the ultimate performance upgrade for your Honda Grom or Monkey 125. CNC-machined and case-hardened for maximum durability, this sprocket is designed to withstand high-stress riding while providing smooth power delivery.

Key Features

• Lightweight & Durable: Case-hardened construction for extended wear life and reduced rotating mass.
• Optimized Performance: Available in multiple tooth counts to fine-tune your torque or top-end speed.
• Precision Manufacturing: Made in the USA with strict tolerances for a perfect #428 chain fit.

Detailed Model Fitment

Important Fitment Note: 2022+ models use a different bolt pattern than 2014-2021 models. Please select your tooth count based on your specific year:

Also fits: Honda CR 80R ('85), CT 70 ('69-'94), XL 80S ('80-'86), and ZB 50 ('88).

Technical Specifications

• Chain Size: #428
• Inner Diameter: 58mm
• Diagonal Bolt Spacing: 89mm
• Material: Case-Hardened Steel
• Manufacturer: Driven Racing USA

Gearing Guide

The stock rear sprocket size on 2021 and earlier Honda Grom models is 34 teeth.  You can go up to 35 or 36 teeth to increase your low-end acceleration. 

The stock rear sprocket size on the 2022+ Grom is 38t, and you can go up to 39 or 40 teeth to increase low-end acceleration.

A few rules regarding gear ratios for sprockets are as follows:

• Reducing teeth on the front or adding teeth to the rear sprocket delivers increased torque, increased acceleration, wheelies, great for tracks with short straights / urban riding.
• Increasing teeth on the front or reducing teeth on the rear delivers increased top-end speed, lowers RPMs, better gas mileage, great for tracks with long straights / open road cruising.
• Reducing 1 tooth on the front sprocket is equivalent to adding 3 teeth on the rear sprocket
• The bigger the rear sprocket, the lower the gearing and the faster the acceleration

Honda CR 80R ('85), Honda CT 70-3Spd ('69-'94), Honda Grom 125, Honda XL 80S ('80-'86), Honda XR 70R ('97-'99), Honda ZB 50 ('88), Various unlisted makes/models