On Jul 13, 5:08*pm, "Hustlin' Hank" wrote:
I need some ideas. It is a Yamaha atv. Battery shows 12.9 volts and
turns the engine over fine, but won't start. When I hook up a battery
charger it starts right up. Battery voltage when running is 14 volts.

Any ideas?

Hank ~~~knows something has to be wrong

14 v running means the charger system is probably good, you could
check voltage as it starts, but its most likely a weak battery without
any capacity, clean all connections first it could be something dirty
corroded or loose now alllowing full amperage to the starter.