HD put out service bulletin M1304 for all 07 and later twin cams which states:
"When a motorcycle is at operating temperature and in neutral, a rattling sound may be heard on the right side coming from the area of the transmission side cover. This sound is normal and is referred to as neutral rattle. To verify the sound is neutral rattle, pull in the clutch lever and hold it for 10 to 15 seconds. If the sound stops, it is neutral rattle. Neutral rattle is caused by the necessary backlash within the first gear pair." You can still have your dealer check this out for FREE under your warranty