Classic Motorcycle Build

Harley 45 Engine Assembly

After the bottom end was completed and the oil scavenger pump in place, the idler and cam gears were next to be installed on the Harley 45 engine. Starting at the flywheel mark, the gears in cam case need to be installed correctly in order to properly transmit power to the four cam gears, crankcase breather, timer, oil pump and generator.

Harley 45 flathead engine assembly

Harley 45 Generator

To prevent too much oil from getting on the generator ball bearings, Harley generators have an oil deflector, sometimes called a slinger. Two different kinds of oil slingers are found on the 45 motor; one works with the two-brush generator and the other on the three-brush generator.

On a three-brush generator, the oil deflector requires a spring between it and the bearing to hold it up against the gear. There is a spring-loaded breather on the inside of the Harley 45 cam cover that rides on the end of the gear.

Harley flathead generator gear

The oil deflector used on later two-brush generators has a built-in collar. The gear is drawn onto the shaft with a nut until it pinches the oil deflector tight against the inner race of the ball bearing. This sets the location of the gear and locks the armature in place. The oil deflector on two-brush generators also sets the location of the gear.

Cycle-Electric generator

Although I had a rebuildable Harley 12v generator (65A), I opted for a new 12v Cycle-Electric generator, which is a nice upgrade if you plan on riding your bike with some piece of mind. When converting from a three-brush generator, you will need to enlarge the mounting holes on the early cam cover from 1/4" to 5/16". This is easily done with a 5/16" drill bit. You will also need a pair of 5/16" mounting bolts, and the correct generator gear and oil deflector.

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Install Cam Gears

After the idler gear and generator are in place and checked for proper clearance, the cams can be installed. Most 45 engines left the factory with one steel shim washer behind each cam, but there are some engines that will require two shims. Hopefully you took notice of this during the disassembly process.

Shim clearance can be checked once the cams are in place. With the tappets not yet installed, stick a feeler gauge down into the open tappet-block hole. If all is well and everything clean, install the shims and cams in their prospective spots.

Harley-Davidson 45 flathead

Harley 45 Cam Timing

Install the cams in this order: rear exhaust, front intake, rear intake, and front exhaust. Remember to install the shims behind them. Tip: if the motor won't be started for several months, coating the cams with assembly lube is a good idea.

Harley 45 cam timing is critical to a running engine. First, set the flywheel mark in the window. The pinion gear will only go on one way. Align all cam timing marks off the pinion gear mark. The cams are aligned to each other by lining up the notches on the outer face. They notches won't line up exactly - that's how they are, but when all cams are in place, slowly rotate the engine. As they all turn together check that they are lined up.

Harley-Davidson 45 flathead

Temporarily install the cam cover without a gasket. Use a soft mallet to tap the cover on if necessary, and install three or four bolts. Once the cover is on, slowly turn the motor over by hand. Check for binding or excessive play. If there is either, stop and find out why.

Harley-Davidson 45 flathead

If all is well, remove the cam cover and lay the engine on it's left side. Pour about a 1/4 pint of engine oil over the cams for lubrication. Install the cam cover with a new gasket using a non-hardening sealant. Install and tighten all cam cover bolts.

Install Oil Feed Pump

After the cam cover is on, the oil feed pump can be mounted. First install the (new) gasket, then slide the oil feed pump onto the three studs, then hand-tighten the three nuts and washers. While turning the engine over slowly by hand, press lightly on the pump until you feel the drive cogs mesh and drop into place. Tighten the three nuts and washers.

Harley-Davidson 45 flathead oil feed pump

Install Tappet Blocks and Tappets

Harley-Davidson flathead 45 tappets

read Harley 45 Cylinder Assembly

read Harley 45 Flatheads