I was parked today waiting for a friend to join me for a ride when I shifted into neutral and when I let out the clutch I noticed a slight vibration and a soft growling sound. I pulled in the clutch and it disappeared. The only thing I have done clutch wise is switch to synthetic oil. Is this something I should worry about? Problem is, I have only had the bike out on the road twice after almost 7 months in the garage (long winters in AK). What do I need to check, if anything? I look forward to your wisdom.