900 engine in 650 chassisconversion

Well, I believe the stator and rotor are bigger, so is the starter. I can measure my buddies engine and let you know how many inches wider it is... for sure it is bigger and heavier all over.
I tried to find the exact quote on the subject - read it on DragBike forum last year...
I believe the front sprocket needs to be offset as much as 19mm to get it to line up with the back one.

Went to DragBike and found the thread you are talking about. The only thing stated is regards to the heavier side however outside of that, removing valve and oil filter cover they say it will go in. No mod to front sprocket.