Normal operational use of your Harley Davidson Sportster will eventually lead to wear on the clutch plates in the transmission. Over time this wear will create excessive play in the clutch plates. Excessive play will probably be noticed in the clutch lever, with symptoms such as clutch engagement near the full release position of the clutch lever, instead of more toward the middle of the clutch lever throw. 
Adjusting the clutch plates is fairly simple, and should be done when the transmission oil is changed.
Adjusting the Sportster Clutch
The first step in adjusting the clutch on your Harley Davidson Sportster is to relax the tension in the clutch cable. After relieving the tension on the clutch cable, remove the access plug in the middle of the clutch (derby) cover if equipped or remove the entire clutch cover. Be aware that a spring loaded lock plate rests in an indent behind the cover and sits lightly on the adjusting screw.
After the cover has been removed, gently remove the adjusting screw lock plate.
Grabbing the adjustment screw between two fingers, any play in the clutch pack can be felt by pushing and pulling against the screw. To eliminate the play, turn the adjusting screw counterclockwise until it starts to turn hard (play removed) and then turn it an additional turn counterclockwise. Reinstall the lock plate and clutch cover or access cover. If the clutch (derby) cover was removed, replace the o-ring if necessary. Lastly adjust the clutch cable so that there is 1/16 to 1/8 play in the clutch lever.