I'm hoping to explain, simplify and de-myth the lubrication system of the 1000 and 1100 engines. I assume the 1200 is similar, but I have no experience with one.
The crankcase sump holds 3.4 quarts of oil, which is filtered and pressure-fed to the crankshaft main and rod bearings, the primary chain oiler, camshaft bearings and rocker arms. The left side cylinders (2 and 4) are pressure lubricated through oil squirt holes in the connecting rods, while the right side cylinders are splash oiled.
The transmission mainshaft and clutch are lubricated by drip oil collected below the front of the crankshaft, and fed into the hollow mainshaft. Holes drilled into the shaft feed oil to the bushings and gears, and the end of the shaft is open to allow oil to drip into the clutch. The rest of the transmission is splash-oiled.
The rear oil pump is chain-driven by the clutch housing, and pumps any oil collecting in the clutch area back into the engine sump. The front (main) pump is driven by a shaft connected to the rear pump, and also drives the water pump.
Click on pics to enlarge...
The oil pumps use a 4-point rotor turning inside a 5-slot rotor, all rotating in a housing and machined to very tight tolerances. Oil is drawn into the inlet as the cavity between the turning rotors expands, then is forced through the outlet as the cavity contracts. There is a pressure relief valve on the backside of the outlet which is forced open under high pressure, allowing oil to return to the sump.
The pressurized oil from the pump outlet flows into the oil filter housing through a passage in the front engine cover. After passing through the filter element, the cleaned oil flows out through the oil filter center bolt, through a second passage in the front cover, and into the engine oil passages.
As a precaution - for those of us who don't change the oil and filter often enough - there is a filter bypass built into the center bolt. A spring-loaded piston inside the bolt opens a set of ports when the pressure outside the filter element exceeds the pressure within (caused by a clogged filter - shame on us!), allowing un-filtered oil to pass through the bolt, instead of through the filter. Better dirty oil than no oil!
The pressurized and filtered (hopefully!) oil exits the front cover and enters the engine oil passages. The first passage goes from the front cover to the rear of the case, and makes an upward turn just behind the output gear opening. This is where the primary chain oiler passage branches off. The main passage continues upward to the case top, where it turns inward and joins the upper main passage. The upper passage runs the length of the case, and feeds the oil pressure switch, the left head passage, the right head passage and all 3 main bearing feeds.
The crankshaft is drilled so that the oil at the main bearings passes to the connecting rod bearings. Holes drilled in #2 and #4 connecting rods allow oil to be squirted into the left side cylinders. The right cylinders are lubed by oil thrown off crankshaft bearings and transmission gears.
Both heads receive oil through passages tapped off the upper main passage. An o-ring seals the connection at the case joint.
Oil passes through a restrictor orifice, located in an opening in the head gasket, through a passage drilled through the head, and into the rocker arm shafts. Holes drilled in the shafts oil the rocker arm pivots, and holes drilled through the rockers squirt oil onto the cam lobes. Passages are also drilled to oil the cam bearings.
For those of you with low oil pressure, or delayed pressure buildup, there are several possible reasons - worn oil pump, worn main or rod bearings, a sticking pressure relief valve, a leaking o-ring, or - gasp - a cracked front cover or case.
A slight delay in pressure buildup is probably worn main bearings, allowing the upper passage to drain after shutting down. It would take a second or two to fill.
A longer delay is probably a worn oil pump or partially open relief valve, allowing oil from the filter canister to drain into the sump. There is no anti-backflow valve anywhere in the system.
I hope this all makes sense, and I really hope it helps someone out there! Thanks for your patience...
The crankcase sump holds 3.4 quarts of oil, which is filtered and pressure-fed to the crankshaft main and rod bearings, the primary chain oiler, camshaft bearings and rocker arms. The left side cylinders (2 and 4) are pressure lubricated through oil squirt holes in the connecting rods, while the right side cylinders are splash oiled.
The transmission mainshaft and clutch are lubricated by drip oil collected below the front of the crankshaft, and fed into the hollow mainshaft. Holes drilled into the shaft feed oil to the bushings and gears, and the end of the shaft is open to allow oil to drip into the clutch. The rest of the transmission is splash-oiled.
The rear oil pump is chain-driven by the clutch housing, and pumps any oil collecting in the clutch area back into the engine sump. The front (main) pump is driven by a shaft connected to the rear pump, and also drives the water pump.
Click on pics to enlarge...
The oil pumps use a 4-point rotor turning inside a 5-slot rotor, all rotating in a housing and machined to very tight tolerances. Oil is drawn into the inlet as the cavity between the turning rotors expands, then is forced through the outlet as the cavity contracts. There is a pressure relief valve on the backside of the outlet which is forced open under high pressure, allowing oil to return to the sump.
The pressurized oil from the pump outlet flows into the oil filter housing through a passage in the front engine cover. After passing through the filter element, the cleaned oil flows out through the oil filter center bolt, through a second passage in the front cover, and into the engine oil passages.
As a precaution - for those of us who don't change the oil and filter often enough - there is a filter bypass built into the center bolt. A spring-loaded piston inside the bolt opens a set of ports when the pressure outside the filter element exceeds the pressure within (caused by a clogged filter - shame on us!), allowing un-filtered oil to pass through the bolt, instead of through the filter. Better dirty oil than no oil!
The pressurized and filtered (hopefully!) oil exits the front cover and enters the engine oil passages. The first passage goes from the front cover to the rear of the case, and makes an upward turn just behind the output gear opening. This is where the primary chain oiler passage branches off. The main passage continues upward to the case top, where it turns inward and joins the upper main passage. The upper passage runs the length of the case, and feeds the oil pressure switch, the left head passage, the right head passage and all 3 main bearing feeds.
The crankshaft is drilled so that the oil at the main bearings passes to the connecting rod bearings. Holes drilled in #2 and #4 connecting rods allow oil to be squirted into the left side cylinders. The right cylinders are lubed by oil thrown off crankshaft bearings and transmission gears.
Both heads receive oil through passages tapped off the upper main passage. An o-ring seals the connection at the case joint.
Oil passes through a restrictor orifice, located in an opening in the head gasket, through a passage drilled through the head, and into the rocker arm shafts. Holes drilled in the shafts oil the rocker arm pivots, and holes drilled through the rockers squirt oil onto the cam lobes. Passages are also drilled to oil the cam bearings.
For those of you with low oil pressure, or delayed pressure buildup, there are several possible reasons - worn oil pump, worn main or rod bearings, a sticking pressure relief valve, a leaking o-ring, or - gasp - a cracked front cover or case.
A slight delay in pressure buildup is probably worn main bearings, allowing the upper passage to drain after shutting down. It would take a second or two to fill.
A longer delay is probably a worn oil pump or partially open relief valve, allowing oil from the filter canister to drain into the sump. There is no anti-backflow valve anywhere in the system.
I hope this all makes sense, and I really hope it helps someone out there! Thanks for your patience...