How to Change the Fluids in a 2003 Harley Davidson Road King

by Chris Gilliland
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The three most critical fluids used by a 2003 Harley-Davidson Road King are housed within the the motor, primary drive and transmission. These fluids must be drained and refilled regularly - Harley-Davidson recommends 2,500 mile intervals - to ensure that your Road King's power train components receive their required lubrication. Doing so is straightforward enough for most Road King owners to tackle with little trouble using only a few tools.

Step 1

Warm the motor up for 3 to 5 minutes, letting it idle in place or by taking the Road King for a short ride. Stop the motor once it has warmed and mount the motorcycle on a service stand to support it in an upright position.

Step 2

Place a large drain pan below the Road King's oil sump, positioned under the motor. Unscrew the oil tank and transmission filler caps from the right side of the Road King.

Step 3

Remove the motor oil drain plug from the side of the oil pan, facing the front of the motorcycle, using an Allen wrench. Unscrew the transmission oil drain plug from the bottom of the oil sump, using an Allen wrench. Unscrew the drain plug from the outer primary cover, positioned just below the round derby cover, using a Torx driver. Allow all three fluids to drain completely.

Step 4

Clean all three drain plugs, using a shop towel, to remove any buildup or debris from the plugs' magnetic tips. Pull off the metal O-rings from the drain plugs, and replace them with new O-rings.

Step 5

Screw the drain plugs into their respective locations, using an Allen wrench and a Torx driver. Tighten the drain plugs to 14 pound-feet, using a torque wrench.

Step 6

Unscrew the oil filter from the front of the motor using a strap wrench. Catch any oil remaining in the oil pump to drain. Fill a new oil filter with 20W-50 motor oil, and screw it into place on the motor. Tighten the oil filter by hand until it is seated snugly against the motor.

Step 7

Fill the oil tank with three quarts of 20W-50 motor oil, and the transmission with one quart of Harley-Davidson transmission oil. Screw the oil tank and transmission filler caps into place.

Step 8

Unscrew the derby cover bolts, using a Torx driver, and pull the cover away from the outer primary cover. Fill the primary with up to one quart of Harley-Davidson primary fluid, stopping when the fluid is level with the bottom of the clutch assembly held within the primary cover. Screw the derby cover bolts in place, using a Torx driver.

Step 9

Wipe away any spilled oil from the motor, primary or transmission before starting the Road King, using a shop towel.

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