I have notice a tapping sound in the head area of the engine. It is not constant but seems to be most prominent at 40mph and 2k rpm. bought a mechanical ears and with the engine at idle you can clearly hear a hard tap when listening on the head bolts as well as the head itself. the sound is barely heard when on the bolts at the bottom case and around the jugs. The bike is a 2007 electra glide with 78000 miles however the engine was mod to on the upper to a 103ci with high compress pistons, roller cams with compression release, adjustable pushrods. was dino with a racing tuner. this was done at 63000 miles. any thoughts. oh yeah when listening with the mechanical ears you can deffinintly hear what I would say metal tapping metal.