RK Racing Chain GB420MXZ-100 Gold 100 Link Heavy Duty MX Racing Chain

Our review of the GB420MXZ-100 finds it ideal for the serious motocross racer seeking the lightest, strongest non O-ring chain for 50cc to 125cc open class use. The bottom line: this chain delivers class-leading tensile strength and a durable construction without the added weight of O-rings, making it a clear choice when maximum strength-to-weight matters most on race day. Riders who prioritize reliability and long wear life will appreciate the engineering and finish of this specific 100 link version.

Key Features

• Chrome-moly construction: The chrome-moly steel plates and components provide high strength while keeping overall weight low for nimble handling.
• Seamless rollers and bushings: These reduce friction and improve wear life so the chain maintains performance over extended racing use.
• Oversized alloy pins: Special alloy pins increase shear resistance and deliver a higher maximum tensile strength for hard landings and big torque loads.
• HIT heat treatment: All parts are heat-treated with RK's Heat Induction Transfer process to improve durability and reduce the chance of premature failure.
• High tensile rating: Rated to 5000 ft-lb tensile strength, the chain is built to withstand professional level stresses in lightweight motocross classes.
• Clip master link: Uses a clip style master link for straightforward installation and field repairs without specialty tools.

Who It's For

The GB420MXZ-100 is aimed at professional and serious amateur riders competing on 50cc to 125cc open class bikes who need a non O-ring chain that sacrifices minimal weight while offering maximum strength. Its light weight and 5000 ft-lb tensile rating make it especially suited to racers who change components for on-track performance and who value longevity under aggressive use.

Riders who prefer sealed O-ring chains for minimal maintenance or who ride heavy displacement street bikes should look elsewhere; this chain is optimized for racing environments where service intervals and dirt exposure are expected parts of ownership.

Pros & Cons

Pros

• Exceptional strength-to-weight thanks to chrome-moly construction and oversized pins.
• Durable heat-treated components that extend wear life for racing applications.
• Seamless rollers and bushings reduce friction and help the chain run smoothly over time.

Cons

• Non O-ring design requires more frequent cleaning and lubrication compared to sealed chains.

Specifications

Brand	RK Racing Chain
Model	GB420MXZ-100 (420 Series)
Link Count	100 links
Maximum Tensile	5000 ft-lb
Weight	1.76 lb
Pin Length	15.7 mm
Master Link Type	Clip

Our Verdict

The GB420MXZ-100 is a focused racing chain that delivers an outstanding balance of light weight and raw strength, making it a strong value for competitive riders in the 50cc to 125cc open classes. Its chrome-moly construction, HIT heat treatment, and robust pins mean fewer failures under race stresses, though riders should be prepared for regular maintenance versus sealed alternatives.

Frequently Asked Questions

Is this chain suitable for professional motocross racing?
Yes. With a 5000 ft-lb tensile rating and race-oriented construction, this chain is built for professional level 50cc to 125cc open class racing.

Does it use an O-ring seal?
No. The GB420MXZ is a non O-ring chain designed for the lightest possible weight and maximum strength; it will require routine cleaning and lubrication.

What type of master link is included?
It uses a clip style master link for easy installation and field repairs.