Classic Motorcycle Build

Harley 45 Engine Teardown and Inspection

Text and Pictures by Mark Trotta

Purchased as "parts only, non-running", this Harley 45 flathead engine was locked solid - no flywheel movement at all. But the VIN number was unmolested and belly numbers matched. If the motor came apart cleanly and without damage, it would be worth the effort.

harley 45 engine teardown

Missing pieces included cylinders and heads, generator, timer, intake manifold, and carburetor. But overall, what was left of the motor looked good considering it's age.


Visual inspection of the engine cases revealed no cracks and no broken bolts. Also encouraging was unstripped factory screw heads--something uncommon for an 80-year-old engine!

vintage Harley engine teardown

According to the previous owner, the motor "sat outside for awhile". As a precaution before starting disassembly, I decided to soak the engine in oil for a while. This would allow every nut and bolt to come off as easily as possible.

Harley WLA 45 rebuild

After removing the Military-style breather tube, I scrounged up a plastic tub that the motor would fit into, and filled it with four gallons of automotive engine oil.

harley 45 engine teardown and inspection

The motor soaked for two months before being pulled out of the oil, then placed into a flat drain pan. Most of the cleaning was done with cans of brake parts cleaner, compressed air, and shop towels.

Harley engine soaking in oil

Oil Pump Removal

On a Harley 45 engine, the generator, oil feed pump and ignition timer need to be removed before the gear cover can be removed. One bolt and three nuts hold the feed pump on.

The gear cover is set onto dowel pins and is secured by ten screw-head bolts.

harley 45 cam cover removal

A little coaxing with a gasket scraper and light hammer.

Harley WLA engine teardown and inspection

As is evident from the pictures, the motor collected a lot of dirt and debris from sitting outside with no top end.

A two-jaw gear puller helped remove the pinion gear.

engine teardown harley 45 valve tappets

The scavenger oil pump is mounted with four studs and nuts. Removal required light tapping with a small hammer and punch.

harley 45 remove oil pump

The breather valve is an integral part of the scavenger pump. The small screen between the breather valve and crankcase port will be cleaned or replaced.

Harley WLA engine teardown and inspection

Harley 45 engine cases are held together with two bolts that thread into the case, and five studs with nuts on either end.

harley 45 split engine cases

The studs were driven out with a flat-ended punch and hammer.

harley 45 split engine cases

With the help of a gasket scraper and light hammer, the right case separated from the left case.

harley 45 engine cases


Remove Flywheel Assembly

The flywheel assembly was pressed out of the case in a hydraulic press.

press flywheel out of engine case

The reason for the frozen flywheel was now apparent.

harley 45 separate engine cases

The roller bearings and cages were rock solid from years (perhaps decades) of non-use.

Harley 45 roller bearings and cages


Remove Tappet and Tappet Blocks

Even after the soaking, the valve tappets and blocks wouldn't budge.

Harley 45 right side engine case

I decided to stop and put the the right-side engine case back into the container of oil, where it soaked for another two weeks. But even after the second soaking, three of the four valve tappets and blocks wouldn't budge.

engine teardown harley 45 valve tappets

Next, the engine case was placed in an oil drain pan, then sprayed down with penetrant. Every morning, I'd spray them down, and then again in the evening. After a week's time, they still wouldn't move.

harley 45 right side engine case

Finally, I heated the valve tappets and blocks with a torch (Map gas), then slowly tapped them out with a hammer and punch.

harley 45 valve tappets and guides

Once the tappet blocks were out of the case, they were placed in a vice.

harley 45 valve tappets

A tappet removal tool is required to remove tappet from the block.

harley 45 valve tappets

The tappet removal tool (Harley #11960-38) fits 1938-1973 Harley 45 Flatheads, also fits UL and VL big-twin flatheads.


Engine Parts Inspection

After the engine was stripped down to left and right cases, visual inspection revealed no cracks, broken edges, or stripped threads.

Harley WLA engine cases

The cam cover cleaned up nicely.

harley 45 gear cover

Very often, you'll find Harley gear cover bolts stripped out due to a previous owner using too small a flat-blade screwdriver.

harley 45 gear cover bolts

Most of the bolts on this engine will be re-usable.

After being cleaned up on the wire bench wheel, the cams were found to be too pitted for further use.

harley 45 cams


Related Articles:

Install Harley 45 Cams
Assemble Harley 45 Cylinders
Harley 45 Bottom End Rebuild
Harley-Davidson WLA Military Bike
DIY motorcycle engine stand

Read: DIY Harley Engine Stand