When you hit the start switch do you hear a clicking sound from the start relay?
If so, then take a piece of wire and then unplug the small wire that gos to the starter solenoid. Now place one end on the battery pos terminal, the other end touch the solenoid connect that the small wire was hooked to. (Make sure the bike is in neutral) Did the starter now turn normally? If so the problem is in either the starter relay, or in the start wiring from the start switch to the relay. In this circuit you will have two plugs that the wire runs through. Make sure the contacts are good. Also the wires to the start switch from the plug for the right hand controls are white and black and red and black Find these two wires and check with a volt/ohm meter set to low ohms. Put one probe to one terminal and the other probe to the other terminal that these wires are connected to. Press the start switch. ANY resistance indicates a bad start switch. If this check is normal then leave the probe in the black and red cavity and go to the start relay. Place the probe to this end of the black and red wire. With the VOM set for low ohms what is the reading? If ANY ohms is indicated check the wire back to the plug for it should read O ohms. If everything checks normal remove the start relay and take it to any auto parts store and pick up an identical replacement and install. Does the starter now work? If yes you found the problem. If no, take the VOM and place the black lead to ground and touch the red lead to the black and red wire of the start relay with the relay plugged in. Now hit the start button. What voltage did you read? If it was anything other than battery voltage you are dropping voltage somewhere in the circuits. Since ALL circuits are grounded through the main ground bus on the main chassis of the bike I would start there and check each individual wire for a solid connection at this point. Don't just look at them, examine them. If there is ANY sign of coorosion around the terminal(s) remove the wires and clean them up before reinstalling. If these wires are fine and are solidly connected then go to the battery ground wire and check to make sure it isn't corroded even inside the insulation of the wire.. Make sure that both ends are clean and solidly connected.
If so, then take a piece of wire and then unplug the small wire that gos to the starter solenoid. Now place one end on the battery pos terminal, the other end touch the solenoid connect that the small wire was hooked to. (Make sure the bike is in neutral) Did the starter now turn normally? If so the problem is in either the starter relay, or in the start wiring from the start switch to the relay. In this circuit you will have two plugs that the wire runs through. Make sure the contacts are good. Also the wires to the start switch from the plug for the right hand controls are white and black and red and black Find these two wires and check with a volt/ohm meter set to low ohms. Put one probe to one terminal and the other probe to the other terminal that these wires are connected to. Press the start switch. ANY resistance indicates a bad start switch. If this check is normal then leave the probe in the black and red cavity and go to the start relay. Place the probe to this end of the black and red wire. With the VOM set for low ohms what is the reading? If ANY ohms is indicated check the wire back to the plug for it should read O ohms. If everything checks normal remove the start relay and take it to any auto parts store and pick up an identical replacement and install. Does the starter now work? If yes you found the problem. If no, take the VOM and place the black lead to ground and touch the red lead to the black and red wire of the start relay with the relay plugged in. Now hit the start button. What voltage did you read? If it was anything other than battery voltage you are dropping voltage somewhere in the circuits. Since ALL circuits are grounded through the main ground bus on the main chassis of the bike I would start there and check each individual wire for a solid connection at this point. Don't just look at them, examine them. If there is ANY sign of coorosion around the terminal(s) remove the wires and clean them up before reinstalling. If these wires are fine and are solidly connected then go to the battery ground wire and check to make sure it isn't corroded even inside the insulation of the wire.. Make sure that both ends are clean and solidly connected.