Operating Oil Pressure

Operating oil pressure may be checked as follows:

Fill oil tank with Harley-Davidson 75 oil. Disconnect oil pressure switch wire at top of switch and remove switch. Install Oil Pressure Gauge, Part No. 96921-52. Attach gauge bracket to motorcycle and road run or simulate road running until engine is completely warmed. A full operating temperature is essential for accurate gauging. Pressure should be 25 to 28 pounds per square inch at 20 mph. At 30 mph. and over, pressure should be steady at 35 to 38 pounds.


If motorcycle is equipped with an oil filter, thoroughly wash the filter element in clean gasoline or solvent at least once every 2,000 miles when the engine oil is changed. Blow out element with compressed air before installing.

To remove the filter element, take off acorn nut, fiber washer and cup. Remove element retaining nuts and metal element retainer. Then pull element off stud. If upper metal retainer (retainer with five holes in it for oil passage) comes off with the filter element, make sure that it is reinstalled as the upper retainer whenTeplacing the element.

Replace filter element every 5,000 miles. OIL FILTER (OIL TANK)

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

Wash filter element (3) in clean gasoline or solvent at 2,000 mile intervals, renew at 5,000 mile intervals. To service filter element, remove cap from oil tank, remove retaining spring (1) and washer (2) and pull out filter. Make certain "O" ring is positioned against filter cup flange (7) when filter is installed in tunk.

SERVICING OIL TANK CAP AND FILLER OPENING. To disassemble, follow order shown in Fig. 3A-2. 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

Revise. 5-68

SECTION 3A Engine - General

Figure 3A-2. Oil Tank Filter - Exploded View

1. Filter clip

2. Cap seal washer

3. Filter element

4. Filter lower retainer

5. Cup spring

6. Cup seal

9. Dipstick and valve assembly

10. Cap gasket

11. Cap cotter pin

12. Cap screw

13. Cap washer

14. Cap nut

15. Cap top 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.


1. Gravity feed from tank to feed pump.

2. Feed (pressure) section of oil pump.

3. Check valve prevents gravity oil drainage from tank to engine. Builds up oil pressure to operate oil signal switch.

4. Oil pressure regulating valve limits maximum pressure. Surplus oil is dumped bar": into gearcase.

5. 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.

6. Oil is forced through passages or external oil lines to lubricate rocker arm bearings and rods, valve stems, valve springs and push rod sockets. A branch passage supplies oil to the hydraulic lifters. On some models, oil supply is filtered through oil screen (6A).

7. Front chain oil. Oil is bled from by-pass oil for front chain lubrication. On 1964 and earlier models, chain oiler screw on pump is adjustable.

8. 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.

Figure 3A-4. 1963 to 1965 Oil Feed Pressure System
Figure 3A-4A. 1965 and Earlier Oil Scavenger System

9. Oil flows from the rocker arm bearings through push rod covers into the gearcase compartment, lubricating push rods and tappets.

10. Rotary breather valve is timed to open on the downward stroke of pistons, allowing crankcase exhaust air pressure to expel scavenge oil from crank-case breather oil trap into gearcase. Breather valve closes on upward stroke of pistons, creating vacuum in crankcase.

During this interval, the small ports in breather valve line up with passage in crankcase. Oil is then retrieved through passage by vacuum from breather oil trap in crankcase, and (on 1965 model) from front chain compartment.

11. Oil blown and drained into timing gearcase (steps 4, 8 and 9), lubricates generator drive gear, timing gears and gear shaft bearings.

12. Gearcase oil settles in gearcase sump from where it returns to pump.

13. Scavenge (return) section of oil pump.

14. Engine oil return to tank.

15. Exhaust air baffle and transfer passage to breather oil trtp.

16. Breather oil trap with screen.

17. Oil transfer passage to breather valve.

18. Crankcase exhaust air escapes from gearcase through outside breather tube on 1965 and later model. Air exhausts to front chain guard on earlier models.

19. Return line from chain housing (1965 and later).

20. Vent line to oil tank and chain housing.

21. Rear chain oiler.

22. Pressure switch fitting.

engine repair procedure

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