It is a common "quark" that these bikes have. Best advise is to find the best 20/50 V-twin oil that suits your bikes needs wether its dino or synthetic. I wish I could help more but every bike is diffrent and its a trial and error process. Most feel that a good synthetic oil does the job, but at the cost of a lil more top end noise<-------maybe it just me. Im personally going to use dino oil on my next change and see what happens.