diagram from the 250 manual--dk what you found online, but pretty much nothing exists in print for this engine without buying it.
I have the gy6 CDI (separate 2 wire and 4 wire plugs into it) wired as follows--looking at cdi from the back with the plugs on the bottom, first wire colors are based on my gy6 harness. parentheses are the 250 harness/cdi
bottom right corner pin , blue/white to stator (black/red)
bottom middle pin, black/white to coil+ (black)
top right corner pin green to ground
middle top pin green to ground
the above two are tapped together and connected to chassis ground with a lead going from that going to the - terminal on the coil
top left pin black to (black/yellow)
what i'm left with is a black/white wire on the 250 harness (just a ground wire for the cdi) that originally plugged into a cdi black/white lead and the Green and Orange loop from the reverse switch. Tried that open and closed, made no difference.
GY6 cdi and coil tested and work on the gy6.