2011 Harley-Davidson 150 200,000 miles, just bought it about a year ago with 180,000 miles. First thing I did was a engine flush with 1 gal of diesel for 10 min then again with 2nd oil change. Third oil change same but diesel drained on that flush was still tinted green so im pretty sure its as clean as it going to get. Just changed oil last week 5w20 as recommended. Tried another flush this time motor medic 3 bottles with about 3qts of oil still squealing from passanger valve cover. I've had cover off with motor running everything is getting plenty of oil constant sound cold or hot/ normal operating temp. I tried running 5w30 squeal is still there Stethoscope indicates rear most cylinder I believe is #4. I'm stumped any idea's