The circulating pressure oiling system as used on the 61 has been extended to all models. A main feed pump mounted on the gear case cover in the 45, 74 and 80 models, and mounted on the crankcase in the 61 o.h.v. model, introduces oil from the supply tank. A vane type pump is used in the 45, 74 and 80 models, driven by the rear exhaust cam gear shaft. The pump in the 61 is gear type, driven from pinion shaft. Oil under pressure is delivered through pinion shaft, flywheel, crankpin to lower connecting rod bearings and all motor surfaces. In the 61 a by-pass from the main feed line carries oil to rocker arms and valves and a positively timed rotary breather valve driven from the cam gear, carries oil and mist in the motor to the gear case basin. A screen is incorporated in the breather valve. A scavenger gear pump on the crankcase returns oil to the tank.