Operation of H.D. Automatic Mechanical Oil Pump

Illustration No. 12
Sectional View of Automatic Oil Pump.

Operation of Harley-Davidson Automatic Mechanical Oil Pump

The Harley-Davidson oil pump has no check valves to stick, no ball valves to "float," no valve springs to break and no small parts to go wrong.

In illustration No. 12 the rotary valve member R rotates in a left hand direction, looking at it from the top.

After the cam H has raised the plunger P to its highest point, the spring Y returns the plunger, drawing a charge of oil from the tank through the supply pipe S, and through the intake system as follows: Through the channel L, oil reaches the intake port I, in the valve chamber. The port I is connected with the hollow center C of distributor R. From C the oil passes through the opening A into the distributor channel X, then through channel B to pump chamber T.

Just after the completion of the intake stroke of the plunger P the intake port I closes and the discharge port D opens, lining up with channel E. As soon as the plunger is raised by the cam H, the oil in chamber T is discharged through the channels B, X, A, C, D, (D is now opposite E), E and F to the sight feed. From the sight feed the oil is forced to the motor through opening G.

Although the highest 'crank case pressure registered to date in any Harley-Davidson motor tested was 4 pounds to the square inch, the Harley-Davidson oil pump will operate against a pressure of 70 pounds if nec­essary. It is absolutely infallible in its operation. There are no small parts to break. The pump has but two moving parts, the plunger "P" and the distributor valve member "R," rotated by ...a worm gear made integral with one of the gears.

To Adjust the Automatic Oil Pump

When each motor is tested at the factory the mechanical oiler is adjusted so as to (rive the proper oil supply at speeds up to 45 miles per hour. With this adjustment a half pint of oil will average approximately 451 miles (720 miles to the gallon), if Harley-Davidson cylinder oil is used. This adjustment, as it leaves the factory, is such that plenty of oil will be fed to the motor and should not be changed excepting for good reason.

When the machine leaves the factory the mechanical oil pump is not fitted with any definite number of washers at "K." The number of washers varies, depending on the amount required to give the plunger IA2 inch stroke.

If, for good reason it is desired to decrease the oil supply, remove one thin washer.  The adjusting screw "J" regulates the stroke of the oil pump plunger and should be securely tightened after adjusting.

When all the washers have been removed the plunger has no stroke, and nothing can be gained by counter-boring the cover or adding to the length of the screw.

In the tool box will be found two thin washers, each .013 inch thick and two washers each .065 inch thick. To increase the oil supply, add one of the thin washers at a time to the standard washers with which the machine comes from the factory, until the proper oil supply is obtained. Be very careful not to reduce the oil supply below the safety margin. It is better to feed a trifle too much oil than to run the chance of under-oiling, but an absolutely correct adjustment can be made, and should be.