I have had my bike for 2 yrs now and love it. I keep valves adj and oil changed. I would guess the bike has around 2000 hours on it. The noise is heard mostly on idle-1/8 throttle and is heard a little more on the left side. I pulled the clutch apart and could not find anything loose but when I jiggle on the crank it has maby 1/16'' play in it. Also you can here the noise comming more-so from the mid-section (Cylinder) area. I'm thinking rod bearing (hopefully upper) or wrist pin bearing. Has anyone had simular problems or know what this might be? I do ride it alot and when I do, I hammer it, including long dirt road w.o.t.'s every now and then.