Voltage does not start the motor; it takes amperage. Having said that, test voltage should be in the 12.8-12.9 range; voltage of say 10.5 would indicate a dead or shorted cell. If a battery is rated at say 650 CCA (cold cranking amps) that means that the battery should deliver 650 CCA for 30 seconds. A load test typically tests the battery at half the CCA for half the time; i.e., a 650 CCA rated battery should be tested to confirm that it will deliver 325 CCA for 15 seconds.
Most don't understand that to properly load test a battery, it should be fully charged and the let sit for 8-12 hours before testing to get a true reading. A battery can load test good and still be a weak battery. As soon as it is subjected to the load the Harley motor requires to crank the motor; the battery's ability to deliver the rated CCA can diminish very quickly.
I don't know how the battery was prepped for testing or how it was tested so I may be talking out of school. However, I will bet a six pack that if the OP replaces the battery with an OEM battery or a Big Crank battery or any quality AGM battery his problem will be solved. Additionally, if he keeps the battery on a tender, the new battery should last at least 5 years. As usual, JMHO.