After the 1000 mile check-up, the Sportster transmission oil is changed every 10,000 miles. Changing the transmission fluid is a straight forward procedure, and for about $10.00 in parts, is a much cheaper solution than bringing it to the dealer.
Ride the bike to heat up the transmission oil prior to draining. This will help the oil to drain completely. Remove the Sportster transmission oil drain plug using a 5/8 wrench and let the oil drain from the transmission. It is recommended that the motorcycle be straight and level and not leaning on the jiffy stand to ensure complete draining. Before reinstalling the transmissionn drain plug, clean the magnetic head on the drain plug to remove any metal particles that may have collected, and replace the rubber O-ring on the drain plug. Apply a modest amount of Loctite to the drain plug threads, and re-install the drain plug, tightening to 14-21 ft-lbs.
Remove the six torx head screws that hold the clutch inspection cover on, and replace the inspection cover gasket. Remove the two screws that hold the primary chain inspection cover on.
Refilling Transmission Oil
Using a funnel, pour 32 ounces (one bottle) of Harley Davidson Transmission and Primary Chaincase Lubricant into the primary chain inspection hole. According to the Sportster maintenance book, the fluid level should not go above the bottom of the clutch diaphragm spring. Some Sportster owners I know don’t remove the inspection cover, and just replaced the drained fluid with 32 ounces of H-D transmission fluid.
Even though I removed the clutch inspection cover, I poured a full bottle of tranny fluid into the transmission.
After pouring the fluid into the transmission, re-install the clutch inspection cover, using caution to ensure the center spring fits into the recess in the cover. Start all of the cover screws by hand, and then tighten ONLY until they contact the clutch inspection cover. Using a crisscross pattern, tighten screws to 84-108 in-lbs.(hand tighten, but don’t over tighten) Replace the primary chain inspection cover, applying a modest amount of Loctite to the screws.
Road test the Sportster to ensure the transmission shifts normally. When you’re done with the road test, check the transmission drain plug and clutch inspection cover for signs of leaks.