Hey Buellers,I am in the process of putting an xb12r motor into my xb9r bike,I am also doing the primary gear switch on my 9's gear into the 12,since I have the rotor and primary gear from my 9 already in tact,can I just install it as a unit into the 12 or are the rotor assembly housings not compatible? Would save some time from not having to tear both apart if the one will go right in,thanks