Harley Davidson Panhead. Service manual (1948-1957 Rigid) — page 8

1955-1957

GEARCASE

OIL PUMP
GENERAL

The oil feed pump and scavenger (oil return) pump are gear type pumps housed in one pump body and located on rear of gearcase on right side of motorcycle. The feed pump incorporates an automatic bypass valve that reroutes surplus oil (above the amount needed to lubricate the engine) directly to the gearcase. This valve is preset and non-adjustable.
Under normal operating conditions, the pump is a comparatively trouble free unit. The most common trouble with pump operation is the introduction into the pump of a metal or hard carbon chip. If either

gets between the gear teeth, it is possible to shear a key, fracture a gear or break off a gear tooth.

If oil fails to return to the tank, check the scavenger pump gear drive shaft key. When the engine receives no lubrication (oil remains in tank), the drive shaft key on the feed pump drive gear may be sheared. Both of these conditions could be caused by shearing of the oil pump drive gear key. In cold weather slush ice formed from moisture condensation in oil may block oil passages and cause any of above troubles.
DISASSEMBLING OIL PUMP (Fig. 3D-1)

The oil pump may be removed from the motorcycle as a unit only if the engine is removed from the