Originally Posted by r1passedu
just replaced the whole charging system in my bike. stator generator and voltage regulator. when the battery has a full charge it starts right up. i tested the volts @ idle it was 13v. @ 5000 rpm its 14v. so i know its getting juice to keep the bike running. i took it for a ride bike ran great, but when i stopped home and turned it off it wouldnt crank. i just bought this battery too. could it be a bad battery, it charges up but when i start the bike the voltage drops fast and low like it doesnt have enough cranking amps..anyone have this problem?
The easiest way to check to see if the battery is holding a charge (besides checking the voltage directly) is to turn on the head light, since it places a pretty good drain on the battery. If the headlight stays on for a few minutes without dimming down, then usually the battery is at least half way decent. If the headlight goes dim, then the battery isn't holding much of a charge.
However, if the charging system is functioning correctly, then when you come back from a ride, the battery should be fully charged. If it's not, then something may be wrong and/or the battery may not be charging. The battery can also lose its ability to accept a charge. Here's a thread which some information: