Small Engines (Lawn Mowers, etc.): Troy Bulit Rididing Lawnmower, troy bulit, battery cables

Question
Model 28M707  Type 0615-A1  13 HP

Lawnmower doesn't turn over.  Battery is charged, even tried jumping.  When turning the key it makes an electrical sound only.  No manual, given to me by my father. No loose wires that I can see.  Any suggestions on what procedures to follow to narrow down on what the problem is?

Answer
The click is the solenoid engaging.  What is the condition of the battery.  It should read 12.3 volts when fully charged.  If so use a volt meter and measure the voltage at the starter motor when the key is turned.  If other is 12 volts it is the ground.  If not there is a voltage drain on the system.  Resistance is the only thing that causes this.  Loose or corroded wires, switches, terminals or connectors.  

From there check all system grounds, there are more than the battery ground.  You have to find them.  Take your meter and go from switch to switch to see of voltage goes through the switch when the key is turned.. The start system will have these components in it.  The battery, battery cables and connectors,  The solenoid, key switch, pto switch, seat switch and brake/clutch switch.  Some models had a neutral switch in the transmission too.  Is there a back fire suppression switch on the carb? 12 volts should travel from the battery through all of these switches back to the solenoid and then to the starter. Last of all the fuses, are they good?  Check them.  Hope this will help you find the issue.