The 6590HK18, which was engineered as an upgrade to the 4090HK17, delivers up to 50% more CFM by comparison. Delivering 13.8 CFM @ 90 PSI, this unit incorporates a 196 cc (GX200) Honda engine with automatic idle-down, for increased fuel efficiency, and an atmospheric unloading system to prevent oil consumption. ABOUT THE PUMP Heavy-duty, single stage, cast-iron twin cylinders, ball bearings, splash lubricated, cast-iron valve plates with Swedish lamellar reed valves, aluminum alloy connecting rods with automotive-style inserts, multi-finned 11″ flywheel, oil sight gauge ABOUT THE ENGINE 196 cc (6.5 HP) Honda 4 cycle, complete die cast aluminum alloy with cast-iron sleeve, overheard valves, retractable starter, on/off switch, splash lubricated, low oil shutdown