This shows the internal components of the bypass relief.

Oil is fed through the right side of the crankshaft to lubricate the bottom end (connecting rod, transmission gear-teeth & bearings, and the cylinder & piston).  The oil seal in the clutch cover mates with the end of the crankshaft.

The oil gets pumped through the crankshaft and into the rod bearing.  There are drain notches in the sides of the rod that permit the oil to escape.  That oil gets thrown all over inside the bottom end, wetting down the cylinder, underside of the piston, wrist pin, and the transmission gear teeth.

This picture shows a five-speed trans.  See how 4th gear (circled in yellow) & 5th gear (circled in red) do not align with the rod drains.   Ride this thing on the freeway and you spend a lot of time in top gear.  The gear will get hot.  It would be nice to have a steady supply of cool oil rather than the random few droplets that find their way into the mesh.   If you make decent power, both of these gears start to pit.

The oil enters the cylinder at the bottom.  This is the drilled passage.  It is located in the right-rear corner of the cylinder.

The top end oil continues upward through the cylinder head.  The green arrow shows the hole in the cylinder head that mates with the unique keyhole passage in the cylinder.  You can see the keyhole impression from the embossed steel head gasket.

Then the oil enters the head cover.  There is a network of drilled passages in the head cover.  Those passages direct oil to the upper half of the cam bearings.

Right at the horizontal split, each cam bearing has heavy chamfers.  These chamfers are important parts of the lubrication flow path.  You don’t want the chamfers filled in with sealant or debris.

The chamfers on the left-side (yellow) direct oil into a cavity adjacent to the camshaft.  This cavity is pressurized which forces the oil to run through the hollow camshaft.

The chamfers on the right-side (green) direct oil into a reservoir below the cam lobes.  I call it the trough.  The trough (or reservoir) fills with oil.  As the cam rotates, the lobes dip into the trough (like a paddlewheel), pick up oil, and continue around to the cam followers.  The oil coating the cam lobe lubricates the cam followers and cam lobes.  The followers & lobes are subjected to heavy load as the cam actuates the rocker arm and opens the valves.  Each valve spring requires about 130 lbs of force to fully open, so the rocker arm must overcome about 260 lbs of force.  The rocker arms are about 1.4:1 ratio, so the required force is now increased to about 364 lbs.  Torture.