Guys,My Griso has developed a noise from what I think is the left hand side of the engine.I'm not mechanically minded so bear with me.At 3000 rpm I get a real fast what I can only describe as tapping.It sounds like it's coming from the rocker cover.I had the valve clearances double checked and they are correct.Below 3000 its fine and after 3200 the noise goes.The injectors were balanced and set correctly.Any ideas?