I'm building my first one and bought a junker that only has the rear housing as
re-usable for 600. yeah i know i got ripped but i wont do it again. what i need to know is when i replace the rotors do they have to be matched to the e-shaft and front counterweight? and how is using different rotors going to change the spacer used in front of the front counterweight?

 

Bump

 

Rotors have to be within a letter of each other, no matching to the e-shaft or anything. For the spacer you just need to check the play, it may or may not change. There isnt really a way to tell until you put it all together.