Small Engines (Lawn Mowers, etc.): switch, amp meter, solenoid

Question
I have a John Deere 300 gargen tractor. Switch is 3497644. Letters  are S,B,I,A and R. Can you help me get the wiring right?  Thank You

Answer
Have you checked the John Deere message boards?
Does the tractor have an automotive style ignition coil?

S should go to the starter terminal of the solenoid.
I goes to the ignition, the coil shut off.
B is power from the battery.
A is connected to accessories like an amp meter
R is connected to the engine charging regulator which charges the battery

Let me know if this helps.
Eric