After a good 24 hour low amp controlled charge and the battery has set about 2 hours voltage should be about 12.8 volts.

12.8 = full charged

12.6 = 75%

12.3 = 50%

12.0 =25%

With a DC volt meter hooked across the battery terminals and reading 12.7 or so, crank motor and while its cranking it should not drop below 9.6 volts or so and as soon as it starts and throttled up to 2000 rpm or so should read 14.8 or so volts. The crank check shows a rough check of the reserve amperage capacity of the battery while cranking with a 150-200 amp load on it. The 14.8 or so shows a good alternator and if you leave it on a while as the battery is recharged from starting, the regulatory will drop the voltage a little showing itself working. However with the lights and stuff always on it will never drop back much.
When a battery wears out a good charge will show fairly good voltage but the battery can still have very low amperage capacity which will show in the crude crank test but really should be checked after a good charge by removing it from bike and getting a free check at a place like AutoZone that has a fancy load meter check that gives you a print out of the battery health. Battery MUST BE CHARGED to check it.

 

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