St 50 converted using a C90 engine electrical question

I have just fitted a c 90 12 volt cub engine into a 12 volt St 50 when I have come to wire it up the 90 engine has six wires the 50 have 5 coming from the generator. Some are same Red/green= neutral switch. Black and red. White ,yellow, blue. The 90 engine has a green wire the 50 does not. Any idea?
Can I use a 50 carb? They look the similar on the parts diagram. If I up the main jet from #50 to #80? Any advice would be appreciated.

The C90 and ST50 have different ways the ignition system works. The Haynes manual explains it fully, but essentially the ST50's ignition is powered direct from the alternator, whereas the C90 has the ignition powered from the battery.
Check the C50/70/90 manual the 50's and 70's are different from the 90.
I'm not sure about the carb the 90 may have a bigger diameter, it could still run but with slightly reduced performance.

thanks for the advice.