The engine is lubricated by a pressure system circulating oil from the tank through the moving parts and back to tank. For adequate lubrication the tank must contain an ample supply of clean oil at all times.

Oil consumption should be approximately 250 to 500 miles per quart depending on the nature of service, solo or sidecar, fast or moderate driving, how well the engine is

Kept tuneo, ana cnain oner adjustment. n mneaye is noi within this range, see following engine overhaul section.

Remove tank cap and check oil supply at not more than 300 miles after each complete refill. If level is down near "Refill" mark on gauge rod, add oil. When level is down to "Refill" mark, add two quarts. Engine will run cooler and usage will be less with oil level well up in tank.

The oil tank capacity is 4 quarts. The tank is full when the oil level is about one inch from top with motorcycle in an upright position off the jiffy stand. Do not fill above this level because the tank needs some air space. Tighten the cap securely to prevent leakage.

Change oil in new engine after first 500 miles, and at about 2500 mile intervals thereafter. Completely drain oil tank of used oil and refill with fresh oil. If service is extremely hard, hot, on dusty roads or in competition, drain and refill at shorter intervals. Draining should be done while oil is hot. It is not necessary to drain the crankcase for it does not accumulate more than about 5 oz.of oil at any time. At the time of the first oil change, and along with at least every second oil change thereafter, thoroughly flush and clean out tank with kerosene to remove any sediment and sludge that may have accumulated.


The FXS model is equipped with an oil cooler as stan dard equipment. Oil cooler does not require periodic maintenance. When operating the motorcycle in tem peratures below 50 °F (10 °C), it is recommended that the oil cooler cover, provided with your motorcycle, be in stalled; otherwise engine will not warm up to propel operating temperaure.


Combustion in any engine generates water vapor. When starting and warming up in cold weather, especially in freezing or cold weather, the vapor that gets into the crank case condenses to water before the crankcase is hot enough to exhaust the vapor through the outside breather. If engine is run often enough to get the crankcase thoroughly warmed up, most of this water is again vaporized and blowr out through the breather. A moderately driven engine, mak ing short runs and seldom allowed to thoroughly warm up will accumulate increasing amounts of water in the oil tank This water will, in freezing weather, become slush or ¡ce and if allowed to accumulate, will block oil lines and damage the engine. Water mixed with oil for some time forms sludge that is harmful to the engine and causes rapid weat of various working parts. In winter the oil should be chang ed more often than in normal weather. Any engine used for short runs, particularly in commercial service, must have oil changed frequently and tank thoroughly flushed to remove water and sludge, before new oil is put in tank. The farthei below freezing the temperature drops, the shorter the oil change interval should be.

Figure 3-1. Oil Tank Filter — Exploded View

Figure 3-1. Oil Tank Filter — Exploded View


Run engine until it is fully warm. Remove oil tank plug from bottom of tank at right rear corner. Allow all oil to drain. Replace plug. Pour a quart of kerosene into tank and agitate by rocking motorcycle from side to side. Remove plug and drain. Replace plug and fill with recommended grade oil as follows:

Air Temperature (Cold Engine Starting Conditions)

Harley-Davidson Oil Grade

20° to 90 °F - Normal and severe operating conditions

Power Blend Super Premium

Above 40 °F Below 40 "F Severe operating conditions at air temperatures above 90 "F

75 Medium Heavy 58 Special Light 105 Regular Heavy



The oil signal light indicates oil circulation.

If the oil signal lights fails to go off at speeds above idling, it is usually due to low or diluted oil supply. In freezing weather the oil feed pipe may clog with ice and sludge, preventing circulation of oil. A grounded oil signal switch wire, faulty signal switch,or trouble with oil pump will also cause the light to stay on. If the oil signal light fails to go off, always check the oil supply first. Then, if oil supply is normal, look inside the oil tank to determine if oil returns to the tank from the oil return pipe outlet located at front of oil tank near filler hole when the engine is running. If it is returning to the tank there is some circulation, and engine may be run a short distance if necessary. If no oil returns, shut off engine until trouble is located and corrected.


Operating oil pressure may be checked as follows:

Fill oil tank to proper level. Disconnect oil pressure switch wire at top of switch and remove switch. Install Oil Pressure Gauge, Part No. 96921-52. Attach gauge to motorcycle and road run or simulate road running until engine is completely warmed. A full operating temperature is essential for accurate gauging. Oil pressure should be 12-35 psi at 2000 rpm with oil at normal operating temperature.

An acceptable alternate method of checking oil pressure is to connect the gauge, by means of an adapter, at the tappet oil screen.

OIL FILTER (Figure 3-1)

The tank is equipped with a large mouth filler opening and a screw cover with oil filter attached.

Oil filter element (3) should be replaced at every oil change. To service filter element, remove cap from oil tank, remove filter clip (1), washer (2) and pull out filter. Make certain "O" ring (8) is positioned against filter cup flange (7) when filter is installed in tank.


To disassemble, follow order shown in figure 3-1. Assembly is reverse order of disassembly. Clean and inspect all parts. Replace any that are worn or damaged.

If oil leak should occur between the tank cap and the filler opening, with cap and gasket in serviceable condition, check the lip of the filler opening. A cap drawn too tight will bend the lip of the filler opening resulting in an imperfect seal between gasket and lip.

Drain oil from tank. Using a mallet as a driver and a block of wood as a cushion, bend the lip down until flush with sealing surface of tank cap. Remove nicks and rough spots with emery cloth. Flush tank before refilling.

ENGINE OILING AND BREATHER SYSTEM (The Following Steps Apply to Figure 3-2)

1. Gravity feed from oil tank to feed pump.

2. Feed (pressure) section of pump.

3. Check valve prevents gravity oil drainage from tank to engine.

4. Oil is filtered through oil screen and forced through passages or external oil lines to lubricate rocker arm bushings, shafts, valve stems, valve springs and push rod sockets. A branch passage supplies oil to the hydraulic lifters.

5. Pressure regulating valve maintains correct pressure in system. When oil reaches rocker arms and lifters, regulating valve lifts and allows pressurized oil to flow to pinion gear shaft.

6. Oil is forced through pinion gear shaft to lubricate lower connecting rod bearings from which oil splashes to cylinder walls, piston, piston pin, and main bearings. During cold engine start-up, pressure regulating valve (5) lifts further to allow excess oil to return directly to oil tank.

7. Oil drains from cylinder rocker housing through passage in each cylinder, then flows through hole in the base of each cylinder, lubricating cylinder walls, piston, piston rings and main bearings.

8. Some oil drains from the rocker housing through push rod covers into the gearcase compartment, lubricating push rods and tappets.

9. Rotary breather valve is timed to open on the down-stroke of pistons, allowing crankcase exhaust air pressure to expel scavenge oil from the flywheel compartment through the breather valve into gearcase. Breather valve closes on upward stroke of pistons, creating a vacuum in the flywheel compartment.

During piston upstroke, the small port in breather valve lines up with passage in crankcase and vacuum draws oil from the crankcase breather oil trap.

10. Oil blown and drained into timing gearcase (steps 8 and 9), lubricates timing gears and gear shaft bearings.

11. Front chain oil. Oil is blown into chain case when breather valve is open.

12. Gearcase oil settling in gearcase sump flows to scavenge section of pump.

13. Scavenge (return) section of pump.

14. Engine oil return to tank.

15. Crankcase exhaust air baffle and gearcase cover transfer passage. Air and oil mist is forced into crankcase breather trap.

16. Breather oil trap.

17. Oil transfer to breather valve. On piston upstroke, crankcase vacuum draws trapped oil into breather.

18. Crankcase exhaust air escapes from gearcase and is fed into the rear of the air cleaner housing.

19. Return line from chain housing. On piston upstroke, crankcase vacuum draws oil from chain housing to breather valve. On piston downstroke, oil in breather valve is forced into gearcase.

20. Vent line to oil tank and chain housing.

21. Rear chain oiler.

22. Pressure switch fitting.

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