A scale replacement main gear crafted for XRB-SR series helicopters that use a 4mm main mast. Designed as a direct drivetrain spare to support routine maintenance, fit verification, and tuning work on electric RC helicopters.
When installing, ensure the gear seats squarely on the 4mm mast, confirm axial alignment with the pinion and spur gear mesh, and verify smooth rotation of the main shaft assembly before any test flight. These steps reduce vibration and help preserve consistent rotor tracking.
For tuning and setup, fit this part to restore proper gear engagement after wear, then re-check head geometry and blade tracking following replacement. This item is provided strictly as an RC accessory part for model helicopter drivetrain maintenance.
Use this component as a like-for-like spare if the original main gear shows wear or during scheduled drivetrain servicing; confirm fit with your XRB-SR setup and perform basic mesh and tracking checks after installation.
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