That is not a good comparison, The only thing in common with it and a banshee motor is it is a twin. IMO the 4 strokes are running in the 300ft ect, but you stretch that distance out any farther and they start fallin behind.
You can delet post, the option is next to quote, reply, and edit. Is stock bore 64mm? if so with a 4mm crank I come up with 373cc, and for stock bore and stroke it is 347cc.
Im sure it would work fine, what all do you use your bike for, why is it that you want a +2, as for the chain add 4 inches to you stock ones measurement.
There will be more people on PS that have dealt with them than on here that is where I always here stuff about them. One question, you had Kenz port your cylinders? They are known for 4 strokes Ive never heard of their 2 stroke porting.
Crank and 20 over cylinders bore is still good put pistons in and go 300+ the ride
Noss head shell polished 120+ the ride
Need these parts gone............Pics available of all the parts listed above also.