RK Racing Chain 420 Series Non O‑Ring Racing Chain — 108-Link Gold, Lightweight High‑Tensile for 50–125cc

RK Racing Chain GB420MXZ-108 is a purpose-built, ultra-lightweight non O-ring 420-series racing chain engineered for 50–125cc motocross competition.

Designed for riders who demand maximum strength with minimal weight, the GB420MXZ blends chrome‑moly construction, seamless rollers and oversized alloy pins with RK’s proprietary heat-treatment process. The result is a high-tensile, race‑focused chain that balances durability and low mass for precise power delivery in off‑road and MX/SX conditions. This SKU ships as a 108-link gold chain and includes a clip-style master link for fast installation.

How does this chain deliver strength without extra weight?

The GB420MXZ uses chrome‑moly steel components—seamless rollers, bushings and specially alloyed, oversized pins—that are all heat-treated with RK’s HIT (Heat Induction Transfer) process. That combination increases fatigue resistance and tear strength while keeping the overall mass low, letting the chain handle high loads without adding unnecessary weight.

• Maximum tensile strength: rated to 5000 pounds/feet
• Lightweight: approximately 1.76 pounds per 100 links
• Oversized alloy pins and seamless rollers for reduced failure points
• HIT heat treatment for improved hardness and wear resistance

Which bikes and race classes is the GB420MXZ-108 best suited for?

This 420-series chain is tuned for small‑bore motocross and supercross machines where low rotating mass and high tensile strength matter most. It’s ideal for professional and club racers running 50cc through 125cc open-class off‑road bikes and for street machines up to 150cc where non O-ring chains are specified.

• Designed for 50cc–125cc off‑road racing
• Acceptable for street use up to 150cc (per RK guidance)
• 108-link length fits many common sprocket setups; can be shortened as needed
• Master link supplied as a clip-style connector for quick fitting

What are the key service and sizing details I should know?

Chain pitch center-to-center measures 12.7 mm with a pin length of 15.7 mm, delivering 24.0 links per foot. Wear-life index and longevity depend on riding conditions and maintenance—proper lubrication and tensioning lengthen service, while abrasive race environments will reduce usable life.

• Pin-to-pin center (pitch): 12.7 mm
• Pin length: 15.7 mm
• Link count: 108 links included
• Wear life index: rated up to 300 under ideal conditions

Who this is for: The RK GB420MXZ-108 is aimed at dedicated motocross and supercross riders, mechanics building race setups for 50–125cc classes, and lightweight-focused tuners who prioritize tensile strength and reduced rotating mass over sealed-ring convenience. If you compete or push a small-bore bike hard in off-road conditions and need a robust non O-ring chain that’s easy to service and quick to install, this model is a strong candidate. Note: RK’s sealed-ring warranty applies to non-racing street use, but RK does not warrant chains used in competitive racing.