RK Racing Chain GB420MXZ-104 Gold Heavy Duty 420 Racing Chain

In this review the RK Racing Chain GB420MXZ-104 is evaluated for serious motocross riders who demand a light, strong non O-ring chain. The bottom line: this chain is built for performance-focused 50cc to 125cc open class racers because it pairs a high tensile strength with low weight, making it the clearest choice when durability under racing conditions and minimal rotating mass matter most. The review highlights construction, strength ratings, and real-world fit and appearance feedback to help riders decide if this is the right drivetrain upgrade.

Key Features

• Chromoly construction: Chrome-moly steel rollers and bushings deliver a combination of strength and reduced weight that benefits acceleration and handling.
• Oversized alloy pins: Special alloy pins are larger than typical pins to increase shear strength and resist bending in aggressive off-road use.
• HIT heat treatment: All components are heat-treated with RK's HIT process to improve wear resistance and consistent performance lap after lap.
• High tensile rating: The chain has a maximum tensile strength of 5000 ft-lb, giving confidence for professional-level racing demands.
• Lightweight: At about 1.76 lb for the 104-link length, it minimizes rotating mass for quicker throttle response on small-displacement race bikes.

Who It's For

This chain is aimed at serious motocross racers and mechanics who run professional level 50cc to 125cc open class bikes and need a non O-ring chain that prioritizes strength and low weight. Track-focused riders who value a direct, low-maintenance chain with strong construction will find the GB420MXZ well suited to their needs.

Those who should look elsewhere include riders who require O-ring lubrication for longer service intervals, casual riders who prioritize convenience over peak performance, or machines outside the recommended displacement range where a different series would better match load and wear expectations.

Pros & Cons

Pros

• Exceptional strength for its class with a 5000 ft-lb tensile rating that supports aggressive riding and racing.
• Low weight at 1.76 lb for reduced rotational mass and improved throttle response on small-displacement race bikes.
• Durable construction with chrome-moly components, seamless rollers and oversized pins, plus HIT heat treatment for wear resistance.
• Attractive gold finish and good fitment reported by riders, offering both looks and function.

Cons

• Non O-ring design means more frequent maintenance compared with O-ring chains if long wear life between services is desired.
• Specifically optimized for 50cc to 125cc open class racing, so it may not be ideal for larger displacement or street-focused applications.

Specifications

Series	GB420MXZ (420 Series)
Link count	104 links
Pin length	15.7 mm
Maximum tensile	5000 pounds/ft
Weight	1.76 lb
Master link type	Clip
Wear life index	300

Our Verdict

The GB420MXZ-104 is a focused racing chain that delivers industry-leading strength and low weight for 50cc to 125cc open class racers, representing strong value for riders who maintain their drivetrain and prioritize performance. Its chromoly build, oversized pins and HIT heat treatment make it a sensible upgrade for competitive motocross, while riders wanting longer service intervals or street convenience should consider O-ring options instead.

Frequently Asked Questions

Is this chain suitable for 50cc to 125cc race bikes?
Yes. The GB420MXZ is specifically designed for professional level 50cc to 125cc open class racing and balances strength with low weight for those machines.

Does the chain come with a master link type?
The chain uses a clip-style master link, which is standard for many race chains and allows for secure connection and straightforward installation.

How durable is the gold finish and construction?
Customers report the gold finish looks great and the chromoly construction with HIT heat treatment provides strong durability, though as a non O-ring chain it requires regular maintenance for best wear life.