RK Racing Chain GB420MXZ-140 Gold 140 Link - Lightweight MX Racing

Our review of the GB420MXZ-140 finds it aimed squarely at riders who demand a race-ready, non O-ring chain that sacrifices neither strength nor weight. The bottom line: this chain is for serious motocross racers running 50cc to 125cc open class bikes who want the lightest possible drive chain without giving up tensile strength. The combination of chrome-moly construction, oversized alloy pins and RK's HIT heat treatment delivers a tangible upgrade in durability and performance compared with many stock chains.

Key Features

• Chrome-moly construction: Provides high strength and fatigue resistance for repeated impacts and hard use on motocross tracks.
• Seamless rollers and bushings: Reduce friction and wear, helping the chain run smoothly and extend service life between replacements.
• Oversized special alloy pins: Add shear strength where it matters most, improving reliability under aggressive acceleration and jumps.
• HIT heat treatment: RK's Heat Induction Transfer process hardens all components for better wear resistance and consistent performance over time.
• Lightweight design: At roughly 1.76 lb, the chain lowers rotating mass, which benefits throttle response and handling on lightweight race bikes.
• High tensile rating: A maximum tensile strength of 5000 ft-lb gives confidence for professional level 50cc to 125cc competition.

Who It's For

This chain is best for competitive motocross riders and racers running small-displacement open class bikes who need a non O-ring option that is both light and exceptionally strong. Mechanics and racers who prefer periodic relay-style maintenance will appreciate the clip master link and the chain's focus on peak performance rather than low-maintenance sealing.

Riders who want a maintenance-free sealed chain or those on larger displacement machines should look elsewhere; the GB420MXZ is optimized for performance on 50cc to 125cc race bikes rather than street-focused longevity or O-ring lubrication retention.

Pros & Cons

Pros

• Outstanding strength-to-weight ratio for improved acceleration and handling.
• Durable construction with heat-treated chrome-moly and special alloy pins for longer wear life.
• Seamless rollers and bushings smooth operation and reduce premature wear.
• Gold finish that customers note looks great on many bikes while performing reliably.

Cons

• Non O-ring design requires more frequent cleaning and lubrication than sealed chains.
• Designed for smaller race classes, so not intended for larger displacement street bikes.

Specifications

Model	GB420MXZ-140
Series	420 Series
Links	140
Pin length	15.7 mm
Maximum tensile	5000 ft-lb
Weight	1.76 lb
Master link type	Clip

Our Verdict

The GB420MXZ-140 is a focused racing chain that delivers elite strength in a very light package, making it a smart buy for 50cc to 125cc open class riders who prioritize performance over low-maintenance convenience. Its heat-treated chrome-moly build and oversized pins offer excellent durability for competitive use, giving strong value to racers seeking measurable improvements on track.

Frequently Asked Questions

Is this chain suitable for motocross racing?
Yes, it is built for motocross racers and rated for professional level 50cc to 125cc open class competition.

Does the chain use a master link and what type?
The GB420MXZ-140 uses a clip master link for assembly.

How does the chain balance weight and strength?
Chrome-moly construction, oversized alloy pins and RK's HIT heat treatment provide a high tensile rating while keeping the chain light at about 1.76 lb.