30. ENGINE LUBRICATING SYSTEM.
a. Action of the oil feed pump is indicated by the red signal light located in right side of instrument panel. (Red signal light is normally grounded by the oil pressure switch. When oil pump pressure is built up several pounds, diaphragm opens the signal light circuit.) Action of the scavenger (oil return) pump is indicated (engine running) by oil dripping from 1⁄8–inch hole in oil return tube (large tube) inside oil tank, just back of oil gage rod (dip stick) tube. Since the oil feed pump and scavenger pump are separate units, operated individually, it is possible (due to faulty unit) for either to function alone, thus affecting engine oil pressure and return of oil to the tank. Action of the vent pipe (small pipe) located within the oil tank is of a “breather” nature; its function not being indicated in any manner. Before attempting to diagnose trouble in engine lubricating system, rider must be familiar with and understand indications by instrument panel signal lights (par. [7 f]).
b. Red Signal Light Fails to Burn When Ignition and Light Switch is Turned On.
(1) Check other lights to determine if battery is “up” and that switch and wiring connections between battery and switch are in good order. See that wire connection is secure and screw is tight on oil pressure switch terminal. Failure of light to burn after these checks indicates that either the lamp is burned out or oil pressure switch is faulty.
(2) Test to eliminate the oil pressure switch by removing wire from switch terminal; ground wire on switch body and note if red light burns with ignition and light switch in “ON” position. If light burns, it indicates that oil pressure switch is faulty, and must be replaced. If light does not burn in making this test, it indicates that lamp is burned out. Remove panel cover (par. [119]) and replace lamp.
c. Red Signal Light Continues to Burn After Engine Is Operated Above Idling Speeds.
(1) Check oil supply in tank. If light fails to go out after engine is warm, or after 1 minute of operation, further checks must be made to locate trouble, as indication points to faulty engine lubrication system, or fault in signal circuit. Eliminate the signal system first.
(2) Test oil pressure signal switch to panel signal light circuit. Remove wire from oil pressure switch terminal by turning on ignition and light switch and observing red signal light. If light burns, short circuit in wiring exists. If light does not burn, it indicates normal condition, leaving oil pressure switch of the signal circuit to be tested.
(3) Install new oil pressure switch and start engine. If red signal light goes out after engine is operated above idling speeds, it indicates trouble in oil pressure signal switch. If red signal light continues to burn, it indicates trouble in oil feed pump. Replace pump (par. [44]).