Restore a tired 4 GPM class pressure washer to full output with this 4400 PSI, 4 GPM plunger pump engineered as a direct replacement for Simpson MorFlex 40224, 40225, and 40226 and other 1 in. horizontal-shaft gas models in the 389cc range. The standard SAE bolt pattern, 1 in. shaft bore, and included shaft keys mean the pump lines up with existing engine mounts without machining or new hardware. Strengthened plungers resist scoring from hard-water minerals and small grit, while upgraded water and oil seals hold back the constant pressure cycling that kills budget replacement pumps in a single season. A front-facing oil sight glass replaces the old method, so pre-job fluid checks become a quick visual confirmation rather than a wrench-and-rag routine. The kit ships with the nozzle needle, 3.3 ft. siphon tube, mounting hardware, 2 shaft keys, 4 spring washers, and 4 M8 x 25 mm hex bolts that a homeowner or rental-shop tech needs to complete the pump swap at the bench in about 20 minutes. Use it to power through concrete driveway prep, equipment trailer washdowns, aluminum siding cleaning, farm equipment mud removal, and exterior-paint prep with the 4 GPM throughput that lets 4400 PSI class washers actually recover flow between trigger pulls.