No.
You didn't say where you were checking the voltage. Verify charging voltage by measuring output directly at the voltage regulator. Go between frame ground and the regulator output wire at the main breaker (or pierce wire w/ probe). Measure at 2000 RPM. If 12.8 or lower, disconnect stator from regulator & measure the AC output of the stator at 2000 RPM. Should be about 38 volts AC.
Also make sure the regulator has a good ground using some internal star washers under mounting bolts.