Are you sure it's not the voltmeter? Without starting the bike and having been sitting for a few minutes, what is the battery voltage reading? 12.4-12.7 is generally considered normal for a strong battery. If your meter reads higher than that, it might just be error in your meter.
Low-buck meters from Harbor Freight, etc, list something like +/- 8.0% or more for voltage readings. That could easily be a volt or more of error in the actual meter.