Good chance it's the low tension coil wires. Raise the tank. Two of the coil sets are bolted to the right hand frame rail. Keeping track of where they go, remove the small wires from each coil. Using needle nosed pliers pinch the ends for a tighter fit (see my crappy illustration). Some people also apply dielectric grease before pushing them back on. The third coil is in front right behind the steering neck. A little more trouble to get at. As for your valves they should be checked/set at the recommended factory intervals. You can't go by "noise" as some times the valve face wears quicker than the cam/follower so the valve becomes to tight and will begin to leak. They would have to be extremely out of adjustment before they would cause running issues.