Small Engines (Lawn Mowers, etc.): B&S Wiring, safety switches, volt dc

Question
I recently replace the engine on my 2001 MTD riding mower.  The mower was a B&S 20 hp twin. (slung a rod)

I purchased a 2003 model 21 hp B&S engine that I believe had been on a Craftsman riding mower. (model 407777 type 0137)

Now the question.....  The old motor had three basic wires.  A yellow which was for the safety switch, etc.  The other was a Red/White in a 2 prong connector.

The new motor has a 4 wires in 2 - 2 prong connectors.   A black and white in one connector and Black and red in the other.  

I have plugged my original red/white to the black/red. I believe these to be the AC / DC power from the generator.  

The other connector seems to be a (black) for a ground.  The white is power for the Carburetor Fuel Solenoid.  

The mower of course will crank but not start unless I give it gas directly though the carb. Since there is no power to the solenoid.

So my question is how to power the solenoid and where to plug the original yellow (kill /safety switch).

Thanks in advance
David

Answer
When you turn the key to the "run" position there should be 12 volts on one of the pins.  Depending on the starter switch configuration will depend on which pin.  Use a meter to locate any 12 volt DC pin when the key is in the on position.

There should be a conncetion on the engine block for the safety switch.  All safety switches are eventually conneted to the engine coil shut-off wire, whose terminal is normally located on the engine block.

I would remove the old alternator with the connector from the old engine and tranfer it to the replacement engine.  This will simplify the wire harness.  Most Briggs alternators are inter-changable.

It is very difficult to answer this question but please let me know if this helps or not.  With enough communication we can solve this problem.

Also, do a search for mower wiring schematic or wiring system.  Most manuals only provide a basic schematic but it may help you figure out the problem.  

The solenoid should be easy to correct...once you provide the power to it you should hear it click when you turn the key to the "run" position.

Please let me know your progress.
Eric