2003 Heritage, 88CI, 11K miles, oil level ok. No engine mods other than stage I kit. returning on a road trip I noticed what sounds like a thrashing noise from the engine. Sounds like a dry bearing coming from the front of the engine. At crusing speed I pull in on the clutch and let off on the gas, sound goes away. Clutch in, rev up engine, no noise other than pipes. Let clutch out, noise retuns. Any ideas what this might be?