I have a Z717A that is about 13 years old. When starting the engine it will turn-over with no problem but will not fire right away. The starter will continue to turn the engine over until it starts. Once it starts the engine runs great with no problem. What is happening is that it takes so long for the engine to fire that you almost give up when all of a sudden it fires and starts running. I had a battery terminal actually melt and break loose because the positive cable gets hot because it takes so long for the engine to crank. Didn't realize this when I replaced the battery at the beginning of the season because of a broken terminal that appeared to have weakened from being hot and melting. Thought it was a battery issue - now I have another battery where the positive terminal has broken. Occurred while trying to start. When I touched the wire it almost burnt my fingers because it was so hot. What could be causing the mower not to start right away? Don't want to continue replacing the battery because of it.