I barely get over 13V above 3500 rpm and higher. My regulator is stock mechanical, but does not have the adjustment screws to vary the output. Battery is one year old, will hold a full charge overnight. My rotor slip rings are clean, resistance between the rings is 6.5 "hot"(after a 5 mile ride), resistance between the rings and ground is infinity, and my brushes appear to be in good shape. I have about .1-.2 volt drop through the ignition switch, measured at the brush. That seems to be reasonable based on my research here on the forum. However, the "slap test" is negative- no pull down at all. Given that, I'm inclined to get the rotor rewound before I start fooling with a new regulator or any other mods. I've cleaned every contact I can think of. If the rotor is "sound" and I have 12+ volts at the brush, I should get a good slap test, no?