Eagle/Freya SX bevel pinion upgrade for Hirobo HI0404509  [HI0404509]

Overview of bevel pinion function

This Hirobo HI0404509 SX bevel pinion gear set is an intended replacement for common parts found on Eagle, Freya, EX and SX helicopter models. It serves as the driven/driving interface between the motor and gearbox, and is matched to preserve correct mesh where bevel pinions are used in the tail or main transmissions.

Compatibility is indicated by the listed model references; the set aims to match the mounting patterns and shaft diameters typical of Eagle/Freya/EX/SX components. Confirm shaft diameter and spline count with vendor listings or original diagrams before assuming fitment on other frames.

Installation and tuning notes: fit the pinion so gear faces are parallel and set minimal backlash, check for smooth hand rotation prior to powering up, and ensure alignment with any related spur or bevel gears. Apply a light gear lubricant sparingly and re-evaluate mesh after a short break-in run. Correct pinion setup supports consistent drivetrain timing and reduces noise from worn or mismatched gears.

Use this matched set as a direct replacement when addressing drivetrain faults on compatible Hirobo helicopters, and always double-check dimensions before installation.