HIROBO HRB-0301043 Main Gear Compatible with XRB-SR (4mm Mast)  [HRB-0301043]

Technical Brief for XRB-SR Gear

This is an RC-scale spare main gear intended for XRB-SR series models that accept a 4mm main mast. It serves as a direct replacement to help maintain drivetrain integrity and support fit checks on electric RC helicopters.

During fitment, ensure the gear seats fully on the 4mm mast, check axial alignment relative to the pinion and spur gear, and confirm the main shaft spins smoothly before any flight testing. Proper seating and mesh reduce vibration and help keep blade tracking stable.

Use the part to recover correct gear engagement after wear, then verify head geometry and blade tracking as part of your setup routine. This item is specified as an aftermarket RC accessory for model helicopter drivetrain work.

Fit this component as a like-for-like spare during servicing or when wear is evident; always confirm compatibility with your XRB-SR setup and perform mesh and tracking checks after installation.