• All Sportster oil pumps are unregulated during operation and will deliver their entire volume of oil under pressure to the engine or oil filter mount (respectively).
• The oil pump is geared to the pinion shaft and operates faster (increasing oil pressure) or slower (decreasing oil pressure) depending on the revs used.
  
• Oil viscosity will affect oil pressure.
  • On a cold startup, the oil's viscosity is thicker and this will result in a higher oil pressure but circulation will be restricted somewhat.
  • As the engine warms up, oil gets hot and thinner resulting in higher circulation and a decrease in oil pressure.
• Oil pressure readings are generally taken at the oil pressure switch outlet (oil pressure switch removed).
  • However, the pressure figures for 86-91 models (listed in the FSMs) are based on testing from the tappet hole plug on the engine case between the tappets.
    (although, a gauge can be installed at the pressure switch or the oil pump with the proper fittings)
• Installing a gauge on the rocker boxes will not do a lot of good for comparison or useable results.
  • The oil source is transferred from hydraulic (oil pump) to gravity and slung force by the time it gets to the rockers.
• An adapter can be added at the oil pump housing to split the piping to the oil pressure switch or filter pad (respectively)and the oil pressure gauge.
• Run the engine to normal operating temperature and check the gauge.
• Check your readings against the expected oil pump pressures below or your FSM.

Expected oil pump pressure per FSM's:

As checked with hot oil and a gauge at the oil pressure switch location at the oil pump.
The oil pressure switch has to be removed for the gauge to be installed.

1957-1969: ¹⁾
Minimum: 3-7 psi (idle, with spark retarded)
Normal riding conditions: 10-14 psi (6 psi at 20 mph)

1970-1978: ²⁾
Minimum: 3-7 psi (idle)
Maximum: 15 psi (60 mph in high gear)
Normal riding conditions: 4-15 psi

1979-1985: ³⁾
Minimum: 4-7 psi (idle)
Maximum: 10-20 psi (3500 rpm)
Normal riding conditions: 4-15 psi

As checked with hot oil and a gauge at the plug hole on the engine case between the tappets.
The plug between the tappets has to be removed for the gauge to be installed.

1986-1990: ^{4) 5)}
Minimum: 1-7 psi (idle)
Normal riding conditions: 5-30 psi (2500 rpm)

1991: ⁶⁾
Minimum: 7-12 psi (idle)
Normal riding conditions: 12-17 psi (2500 rpm)

As checked with hot oil and a gauge at the oil pressure switch location at oil filter pad.
The oil pressure switch has to be removed for the gauge to be installed.

1986-1990: ⁷⁾
Oil pressure, when checked at the oil filter pad (oil pressure switch removed), will be 6-10 psi higher than when checked at the tappet plug on the case at idle.
See pressure figures above when checked at the tappet plug hole.

1992-2004: ^{8) 9) 10) 11) 12) 13) 14)}
Minimum: 7-12 psi (idle speed varies from 950-1050 rpm between the different FSMs)
Normal riding conditions: 10-17 psi (2500 rpm)

2013 XR1200X: ¹⁵⁾
Minimum: 16-20 psi (idle)
Normal riding conditions: 40-44 psi (2500 rpm)
Oil pressure relief (50 psi)

• It includes an oil cooler with a thermostat that starts to open at 190ºF (88ºC).
• The oil pump and the head breathers are a new design.
  The oil pump rotors are driven by the cams, the feed rotor is driven off the front intake cam and the scavenge rotor is driven by the rear exhaust cam.