Old (2005) Dixon ZTR 25 HP B&S engine replacement wiring issue

I found a new B&S 25 hp Engine that is said to be an exact replacement for the Original. But it has a different wiring connector. My mower has a lone red wire that is battery hot for charging- I can easily splice that in. But there is another plug with a red and green wire. The red will splice into the fuel solenoid (Gray wire)- so as to open it with key on-- but the new engine diagram shows that the Magneto wire (Black on engine plug) needs to be "grounded with key off." I haven't wired it yet, but my test probe says the mower green wire does NOT go to ground with key off. There is also a big note saying to never put 12v to magneto, it will short it out and ruin it! Am I safe to wire the magneto to the mower's green wire? am I testing it wrong? Maybe all the seat, lever, and brake switches need to be closed?
Thanks in advance
Brian