Harley 45 Scavenger Oil Pump Repair
Text and Pictures by Mark Trotta
Designed in the 1930's and in use into the 1970's, Harley 45 oil pumps rarely go bad unless run with little or no oil for any length of time. It was a well-engineered piece, and often outlives other engine components.
There are two separate oil pumps on Harley 45 flatheads, and each has it's own function.
Feed Pump
The feed pump mounts to the right-side of the engine on the cam cover. It is a vane-style pump which is gravity-fed oil from the tank, then delivers it to the engine under pressure.
Scavenger Pump
The lubrication cycle is completed by the scavenger oil pump. This is a gear-type pump and mounts to the bottom of the right-side engine case. It's job is to return engine oil back to the oil tank.
When purchased, the scavenger oil pump on my 1961 Servi-Car needed to be repaired due to a cracked cover, certainly caused an over-tightened oil pressure switch.
The old cracked cover was a chrome aftermarket piece of unknown origin.
Replacement Oil Pump Cover
There are two styles of scavenger oil pump covers found on 45 flatheads. Harley #26232-38 has a provision for an oil pressure switch and chain oiler. The cover without provision for oil pressure switch is Harley #26231-37.
Pictured: Harley #26232-38 cover for flathead 45 motors.
Remove Scavenger Oil Pump
After removing the oil feed line from the oil tank, the pump can be unbolted from the engine. It is held on with 1/4" studs and nuts.
Removing the pump with the engine in the frame was a bit of a challenge. In hindsight, I should've removed the exhaust system first.
Lying on a concrete floor is not a favorite working position.
There are two flat paper gaskets that go in between the oil pump plates. These gaskets determine end play in the primary and scavenger oil pumps, so you don't want to add any thickness with any kind of sealer.
Instead of using messy silicone sealant, apply a light coat of engine oil to the gaskets, which will allow them to stick in place. Another option would be a light coat of grease or assembly lube.
Install Scavenger Oil Pump
Installation is essentially the reverse of removal.
TIP: If you don't ride much, you can remove and plug the adjusting screw for the chain oiler. Now you'll have a little less oil leaking on your garage floor.
Just remember to oil the chain every now and again.
Oil Pressure Switch
The final step was installing a new switch onto the pump and reconnecting the wire.
CAUTION: It’s easy to crack the outer cover when installing the oil pressure switch. It’s a tapered 1/8" pipe thread, and you'll crack the cover if you run it in too far. I wrapped a little Teflon tape around the threads.
Oil Pump Rebuild Kit
James Gasket 15-1185 Oil Pump Kit fits 1937 through 1973 Harley Flathead 45's.
All James Gasket products are made in USA.
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Notes and Misc
I applied a dab of Permatex 80631 thread sealant on the oil line threads.
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Related Articles:
Harley 45 Engine Teardown and Inspection
Harley 45 Bottom End Overhaul
Harley 45 Cylinder Assembly and Installation
Repair Stripped Threads In Aluminum
Harley 45 Drivetrain
