The feed pump distributes oil to the engine and has fewer lobes than the scavenge pump, allowing for greater pressure development. The scavenge pump returns oil to the tank and has more lobes than the feed pump allowing for greater oil flow.
XL Models: See Figure 3-8. Both rotor sets (3, 4) are driven off a common shaft (2) that is coupled by gears to the crankshaft.
Figure 3-8. Oil pump: XL Models: 1. Body; 2. Gear shaft; 3. Scavenge rotor set; 4. Feed rotor set; 5. Cover
XR 1200X: See Figure 3-9. The feed rotor set (4) is driven by flats on the front intake camshaft (3). The scavenge rotor set (5) is driven by flats on the rear exhaust camshaft (2).
Figure 3-9. Oil pump: XR 1200X: 1. Housing, oil pump; 2. Exhaust camshaft, rear cylinder; 3. Intake camshaft, front cylinder; 4. Feed rotor set; 5. Scavenge rotor set
See Figure 3-10. As the crankshaft rotates, the cavity volume increases between the gerotors on the inlet side of the pump. This creates a vacuum causing oil to be drawn in. The volume continues to increase until it is equivalent to that of the missing lobe on the inner gerotor.
Figure 3-10. Inlet side oil flow: 1. Oil in; 2. Seal; 3. Outer gerotor; 4. Inner gerotor
See Figure 3-11. Continuous rotation moves the pocket of oil to the outlet side of the pump. As the oil moves to the outlet side of the pump, the cavity decreases in volume. This forces pressurized oil out the discharge port. In operation, the gerotors provide a continuous flow of oil.
Figure 3-11. Outlet side oil flow: 1. Seal; 2. Oil out; 3. Continuous flow