internal combustion engines for machine operation; complete industrial power units for machine operation comprising an internal combustion engine mounted in a frame with air cooling system and fuel tanks, sold as a unit; industrial machine engine parts, namely carburetors; industrial machine engine parts, namely lubricating systems comprising oil pumps, oil coolers, oil flow control valves, oil lines, and connections therefor, sold as a unit; industrial machine engine parts, namely reduction gearing and transmission devices comprising clutches, gears, power take-off shafts, and mechanical drive gears, sold as a unit