How to Change a Crankcase Breather Valve on a 1989 Harley-Davidson

Harley-Davidson Evolution engine

Harley-Davidson Evolution motors use a dry-sump type oil return system. Oil is pumped into the tappet blocks, rocker boxes and bottom end bearings. All other components are lubricated by splash and drip. Gravity collects the oil in the bottom of the crankcase where it is picked up by the flywheels and removed by the oil scraper. Oil from the scraper drains into an oil gallery next to the breather valve. The breather valve controls the oil in the gallery. A vacuum forms when the pistons are on the way up and the breather valve is timed to open when this vacuum is being generated. The vacuum sucks oil out of the gallery and into the oil pump pickup area, where it is then pumped back to the oil reservoir.

Things You'll Need

• Bike jack
• Pliers
• Allen driver set
• Standard socket set
• Breather valve
• 1/4-inch torque wrench
• 3/8-inch torque wrench
• Straight edge
• Feeler gauge set

Instructions

1. Elevate the rear wheel of the bike with a bike jack. Place the transmission in first gear with the shifter.

2. Remove the push rod cover clips carefully with a pair of pliers. Slide the upper push rod covers down to expose the push rods.

3. Rotate the rear wheel forward and watch the push rods. Roll the engine over with the wheel until both push rods on the front cylinder are on the base circle of the cam (not being lifted).

4. Remove the four Allen bolts that hold the front rocker cover on. Remove the rocker cover and the middle spacer from the front cylinder. Loosen the bottom rocker box bolts 1/4 turn at a time with a wrench, in series, until the pressure from the push rods is released. Remove the bottom rocker box from the engine. Repeat this process for the rear cylinder.

5. Remove the timing cover on the nose cone with a screwdriver. Remove the timing cup from the engine with a ratchet and socket. Remove the nosecone Allen bolts with an Allen wrench. Pull the nose cone from the engine.

6. Pull the old breather from the engine by hand. Rotate the engine with the rear wheel until the breather valve drive gear timing mark is pointed at the breather valve cavity. Insert the new breather valve into the cavity and align the breather valve timing mark with the drive gear timing mark. Install the end spacer from the old valve.

7. Place the gasket on the engine block and place a straightedge across the machined surface of the block over the breather gear. Measure the breather gear end play between the end spacer and the straightedge with a feeler gauge. The end play should fall between 0.001-inch to 0.011-inch and can be adjusted with thinner or thicker spacers that come in 0.005-inch increments.

8. Reassembly is the opposite of disassembly. Torque the nose cone bolts to 90 to 120 inch pounds. Torque the bottom rocker box to 15 to 18 ft. lbs.. Torque the rocker box cover bolts to 10 to 13 ft. lbs..