Komatsu D21P-6 specifications

D21P-6 engine output and the Hydroshift arrangement

Komatsu's D20/D21 operation manual rates the D21P-6 at 39.5 flywheel horsepower at 2,450 rpm. The 4,070 entry previously labelled horsepower cannot describe that engine output. The manual separately lists the more powerful D21P-6B, so its suffix matters when comparing a machine plate with an advertisement.

The travel controls also differ within this small-dozer family. The D21P-6 shares the two-forward, two-reverse selector arrangement shown for the D21A, P and PL-6 group. The D21P-6B uses the other illustrated arrangement with three speeds in each direction.

The adjacent D20 instructions concern a main-clutch pedal and a different gear selector. Applying those D20 clutch instructions to a D21 Hydroshift transmission would mix two drivetrains.

Keep machine and engine serial breaks separate

The original parts-book extract identifies the D21P-6 machine range beginning at serial 60001 and distinguishes its engine build from the D20P-6 engine. Its intake-manifold listings change at a separate engine-number boundary. A machine serial and an engine serial therefore answer different parts questions; recording only the large model decal leaves that selection incomplete.

Undercarriage parts have their own divisions. The book places the D21P recoil-spring change at machine serial 62725, while the D20P change occurs elsewhere. It also gives separate entries for five- and six-roller track-frame arrangements and for swamp and flat shoes.

A wide shoe by itself does not identify the complete roller-frame assembly beneath it. Compare the installed arrangement with the illustrated parts entry before ordering a recoil or track component.

The shop-manual contents separate the D21P-6 Hydroshift control and hydraulic circuits from the D21P-6B circuits. Steering clutches, steering brakes and the final drives are also treated as different assemblies. A complaint that one track will not turn does not identify which assembly needs repair.

Keep the travel-selector condition and the steering response distinct when describing the symptom to a technician; an engine-output figure cannot diagnose that loss of motion.