We’re ready to install the right-hand side cover.

We’ve oiled the mating surface between the new gasket and crankcase to facilitate later removal, if necessary

The cylindrical oil filter compartment is at the lower right.

The crankshaft oil nipple is between the clutch and timing gear.

The right side cover.

The shiny round bump gives the clutch a little more room.

The oil filter opening is at the lower-right.

The inside view of the right side cover.

The clutch lives in the large round area to the right.

An oil gallery feeds filtered oil from the oil filter opening (bottom left) to both the crankshaft oil collar and to the crankcase oil passage that eventually supplies filtered oil to the camshafts.

The hole on the end of the crankshaft feeds filtered oil to the big ends of the rod bearings.

The oil passage between the oil filter, crankshaft and oil pipes is visible.

Filtered oil from the side of the oil filter opening is fed to the crankshaft oil feed (image center) and, via the right case half and external oil pipes, to the camshafts.

The oil filter cover.

The filtered oil enters the large round hole in the center of the cover, and exits via the smaller hole on its side.

This end of the oil filter faces towards the oil filter cover.

Normally, pressurized oil from the oil pump passes through this paper filter element to the filter interior, then exits the filter through this (big) hole into the cover, and eventually lubricates the big-end rod bearings and heads In many areas of life, there seems to be a couple of mostly-harmless-appearing actions that can have grave consequences down the road: this is one of them.

The oil filter will physically go in either way.

If the filter is installed backwards, the oil filter cover won’t go on quite as far by hand, and one has to wrench harder on the cover bolts.

If the engine is run in this condition, a bad thing happens: no oil is fed to the rod bearings or heads.

To compound this potential problem, these engines do not have an oil pressure sensor – they have an oil level sensor instead. The red oil level idiot light will not warn you if the rods and head aren’t receiving any oil This scares my chickens.

This end of the oil filter faces towards the middle of the engine.

The small opening to the oil filter bypass valve (surrounded by the black O-ring) is visible If the oil filter element becomes really clogged, pressurized oil goes in this end of filter, past the small spring-loaded oil filter bypass valve (visible), and exits at the other end of the filter, without being filtered.

We’ve put the right side cover on, and have threaded the bolts in just one turn so we can check for the appropriate bolt length.

All the bolts should extend about the same length from the side cover.

If some bolts are significantly longer and/or shorter than others, we don’t have the correct bolts in the appropriate holes.

A bolt that’s too short may strip its threads when it’s torqued; a bolt that’s too long may not hold the side cover tight, may strip its threads, or may crack the case half.

All the bolts appear the correct length, so we’ll evenly torque the side cover.

There are a lot of bolts.

A view into the oil filter compartment with the side cover attached.

The oil inlet and oil outlet galleries are visible.

Oil under pressure enters the oil filter compartment (about 4 o’clock; only partially visible), surrounding the outside of the filter element Oil is filtered as it travels through the filter into the cartridge interior Filtered oil travels out the big end of the cartridge, through the cover’s oil passage, exiting through the oil journal near the top center of the picture.

Because dirty oil is trapped outside the filter, it’s a good idea to clean this compartment during oil changes.

The three raised pads at the bottom of the compartment allow oil to get to the oil filter’s built-in pressure relief valve.

The O-ring around the bottom bolt hole probably allows any pressurized oil that’s seeped past the oil filter cover gasket to return to the crankcase, rather than seeping outside the case.

The oil filter has been inserted in the correct direction.

The large opening in the filter faces out, towards the oil filter cover.

Filtered oil travels out of this opening, through the oil filter cover and sidecase, to feed the big-end rod bearings and camshafts.