Note. See Figure 3-12.The paragraph numbers correspond with the callouts.
1. Oil is gravity-fed from the oil tank to the gerotor-style oil pump through a feed hose. Oil enters the feed section and fills a cavity located under the feed pump. See 3.20 OIL PUMP: XL MODELS.
2. The feed pump transfers oil from the inlet cavity through the feed hose to the oil filter mount.
3. Oil flows through the filter mount cavity to the oil filter.
4. Oil enters the peripheral cavity of the oil filter, passes through the filtering medium into the central cavity of the oil filter, and flows into the filter adapter (fitting which connects filter to filter mount).
5. Adequate oil pressure in the filter mount cavity activates the oil pressure indicator lamp switch and shuts off the oil pressure indicator lamp.
6. Oil flowing from the filter adapter opens the check ball. The check ball opens at 10-13 psi (69-90 kPa) oil pressure.
7. With the check ball open, oil flows into the crankcase feed galley.
8. Oil flows through the feed galley in the crankcase to the tappet blocks and hydraulic lifters. Cross-drilled passages intersect the main feed galley and carry oil to each hydraulic lifter. From this cavity, oil is also fed to the piston jets.
9. Oil also enters an intersecting passage in the gearcase cover. Oil flow is then routed to the crankshaft area.
10. Oil enters a hole in the end of the pinion gear shaft and travels to the right flywheel where it is routed through the flywheel to the crank pin. Oil is forced through the crank pin to properly lubricate the rod bearing assembly.
11. Oil flows up passages in the pushrods to the rocker arm shafts and bushings.
12. The valve stems are lubricated by oil supplied through drilled oil holes in the rocker arms.
13. Collected in the cylinder heads, oil flows down the pushrod covers and into the tappet blocks. From the tappet block drain holes, oil flows into the gearcase. After lubricating the gearcase the oil flows to the return side of the oil pump.
14. Feed oil to the rocker area is returned to the gearcase through a passage in the head, cylinder, and crankcase.
15. Oil collected in the sump is splash-fed to the pistons, cylinder walls and flywheel components.
16. Oil in the sump returns to the scavenge pump through an internal passage located in the rear of the sump housing. The downward stroke of the pistons and the scavenge pump feed oil to the oil pump.
17. Return oil fills a cavity above the pump's return gears. The return gears pump oil back to the oil tank.
18. A small amount of oil flows from the feed galley in the right crankcase through a restricted orifice. This sprays the oil onto the rear intake cam gear in the gearcase. Oil is transferred to the teeth of all the cam gears through the gear meshing action.
Figure 3-12. Lubrication diagram: XL models (Red=feed oil, Blue=return oil)