This RC-scale main gear is a replacement item for the XRB-SR series and fits a 4mm main mast. It is supplied to support routine drivetrain servicing, fit checks, and basic tuning tasks on electric RC helicopters.
Key installation items: seat the gear squarely on the 4mm mast, confirm axial alignment with the pinion and the spur gear mesh, and verify the main shaft rotates smoothly without binding prior to flight. These checks reduce vibration and maintain stable rotor tracking.
After fitting, use the part to restore correct engagement following wear, then check head geometry and blade tracking as part of your post-install routine. This product is offered strictly as an aftermarket accessory for model helicopter drivetrain maintenance.
Use this component as a direct spare when the original main gear shows wear or as part of scheduled servicing; always confirm fit with your XRB-SR configuration and carry out mesh and tracking checks after installation.
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