Small Engines (Lawn Mowers, etc.): briggs and stratton electrical, briggs and stratton, 12 volt

Question
I have a 2 cyl B&G (18 hp ?) I am atapting for use other than the rider it came off of. my question is I have three wires, red, white and yellow, the yellow ran to the safeety switches.
What hooks to 12 volt and what hooks to ground? I have the starter circuit hooked up and operating off the key swith, but can't seem to figure out how to get spark.

Answer
 Hello Chris:

 Send me the Model, Type and Code Numbers Off of the Engine, Please. With these I can see a Diagram of the Engine and Better Assist you. However, follow the Coil Shutoff Wire from the Coil. If this Wire is Connected to Ground through the Switch, the Coil will Not Fire. Disconnect the Coil Shutoff Wire and see if you have Fire. If the Coil is Firing with the Shutoff wire Disconnected, then Recheck the Wiring. The Coil Shutoff Wire Should Ground ONLY when the Switch is Turned Off. The Red and White Wires are for the Charging System(Depends on Model). Hope this Helps. Let me know what Happens, Please. Thanks.

 Good Luck

 Respectfully

 John