Classic Motorcycle Build

Harley 45 Scavenger Oil Pump Repair

Text and Pictures by Mark Trotta

Designed and in use since the 1930's, Harley 45 oil pumps rarely, if ever, go bad. Call it over-engineering if you'd like, but they will outlive most other engine components.

Harley-Davidson 45 flathead oil pumps

Feed Pump

There are two separate oil pumps on the Harley 45 flathead, and each has it's own function. The "feed" pump is the one mounted 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.

Harley flathead 45 oil pump install

There are two styles of scavenger oil pumps for the Harley 45 engine. One has a provision for an oil pressure switch and chain oiler.

While installing a new oil pressure switch on my 1961 Servi-Car, the bottom plate of the scavenger pump cracked.

Harley-Davidson 45 flathead scavenger pump

The part that cracked was a cheap chrome aftermarket piece. I should have known better than to re-use it during the engine build.

cracked oil pump cover from Harley-Davidson 45 flathead

So, what started out as an oil pressure switch replacement turned into an oil pump remove and install.

Remove And Install Scavenger Oil Pump

The oil feed line needs to be removed from the oil tank. The pump is held up onto the engine with 1/4" studs and nuts.

Although I have a motorcycle work stand in my garage, it's not wide enough for a trike.

DIY motorcycle work stand

Lying on the concrete floor is never a favorite working position.

Harley 45 oil pump repair

Removing the scavenger pump with the engine in the frame was a bit of a challenge. In hindsight, I should've removed the exhaust system first. Famous last words, "This shouldn't take too long."

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. Another option would be a light coat of grease or assembly lube.

Replacement Oil Pump Cover

There are two styles of scavenger pump covers. 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.

Replacement Scavenger Oil Pump Cover for Harley-Davidson 45 flathead

The adjusting screw is for the chain oiler. If you don't ride much, you can plug this off and have a little less oil leaking on your garage floor. Just remember to oil the chain every so often.

Oil Pressure Switch

The final step was installing the new oil pressure switch onto the pump and reconnecting the wire.

Harley-Davidson 45 flathead oil pressure switch

I used a dab of Permatex 80631 thread sealant on all the oil line threads.

Permatex thread sealant

Read: Harley 45 Gas and Oil Tanks

Harley-Davidson Servi-car oil tank