XCMG XD122 Road Roller Gear Pump – PN 803074402 / CBJ35-F18-S2K | OEM Changzhi Hydraulics | 35 mL/r, 18 MPa

The XCMG PN 803074402​ (model CBJ35-F18-S2K) is an external gear pump​ in the hydraulic system of XCMG XD113 / XD122 road rollers​ — public-channel parts data confirms fitment for these two roller models, with the pump body manufactured by Changzhi Hydraulics. Its job is to convert engine mechanical energy into hydraulic flow and pressure, feeding the roller's vibration, travel and auxiliary hydraulic circuits​ — the "heart" of the machine. The suffix decodes as: CBJ35​ = Changzhi-hydraulics CBJ series, 35 size; F18​ = nominal displacement 35 mL/r, rated pressure 18 MPa; S2K​ = shaft-extension and rotation combination (confirm against manufacturer drawing before install). The broader CBJ35-F series uses an aluminum-alloy housing with bimetal side plates​ and an axial-clearance auto-compensation structure that maintains high volumetric efficiency over long running hours. The operating principle is simple: two identically-sized gears mesh and rotate inside a closely-fitted figure-"8" housing; oil enters between the teeth at the suction port and is carried around to the discharge port.