Excavator Hydraulic Pump 708-2L-00770 708-2L-90721 708-2L-00773 Komatsu PC600-7 PC600-8 PC650-7 PC650-8 Main Piston Pump Pressure Pump The PC650-8 Komatsu large excavator utilizes a dual-pump variable displacement piston system. The hydraulic main pump is a tandem main piston pump consisting of front and rear sections. Common Faults & Diagnostics Weak/Slow Movement on One Pump Side: Internal leakage from worn pistons, valve plate, or slippers in that section. Diagnose by