Heavy Hitter Zero XB 420 Primary Chain Drive Conversion Kit

The Heavy Hitter Lightweight 420 Primary Chain Drive Conversion Kit is the best-performing drivetrain upgrade for the Zero XB. Stock belts can’t handle serious torque, especially with upgraded motors or controllers, and other chain kits add unnecessary weight or resistance. This kit fixes it all — stronger, lighter, and designed with the least rotating mass and resistance of any 420 primary kit on the market. After years of breaking parts and refining designs, we found the perfect combo: a 7075 T6 billet aluminum rear sprocket to keep weight down, a nitrided 52100 tool steel front sprocket for maximum durability, and a non-O-ring Japanese chain with master link to keep rolling resistance at an absolute minimum. We tested vulcanized rubber sprockets for noise reduction, but they trapped dirt and mud between the chain links — accelerating wear and killing performance. That’s why this kit is built for speed, not silence. The conversion keeps your stock gear ratio and OEM motor alignment intact, with precision machining that extends sprocket life and keeps things smooth at high RPM. It’s louder than a belt drive, sure, but no louder than other chain kits — and if you ever want it quieter, you can swap to an O-ring chain (at the slight expense of performance). Whether you’re on stock power or pushing EBMX, Sotion, or Torp setups, this kit is race-proven, lightweight, and built for abuse. ⚠️ Important Notice:  When installing, make sure your chain tension is loose not tight! Any chain drive that you install should have loose chain tension! Please check the fitment tab for important motor info. (MORE INFO HERE) Features 7075 T6 billet aluminum rear sprocket (black anodized) 52100 tool steel front sprocket with nitrided black surface coating Lightest primary kit on the market for maximum performance 42-link Japanese non-sealed chain with master link included Maintains OEM gear ratio and motor alignment Precision-machined for long sprocket life and smooth performance Best Efficiency Rated Chain Drive on The Market   Fitment Zero XB Important Notice: When installing, make sure your chain tension is not tight! Any chain drive that you install should have loose chain tension! Download Tech Sheet (Assembly & Torque Specs)