Alright well I was cleaning my rotors today only to find out an apex groove was bad... So I decided to buy new rotors... Well new/used. LOL Anyways the weights of my rotors are D & E. I was wondering do I necessarily have to buy D & E weight rotors in order to avoid balancing the assembly? Or can I just buy a pair from another motor? I am still gonna use the eccentric shaft and counter weight that I already have...

 

wounter weight must match rotors. eshaft... probably same as mazdatrix shows one for two.

 

The rule of thumb is to use rotors within one letter of the other, so D and E are fine. Also if you're using s4 rotors be sure to use s4 counterweights, s5 rotors use s5 counterweights, you get the picture.

 

Well, I thought that the e-shaft and the rotors were balanced together. I am actually curious about that question also, as I might have to use rotors from 1 engine and an e-shaft from another (see my current thread for the reason why )

 

They probably are, and you can get the rotors balanced on the E-shaft. Its about $350.

This is probably the 'correct' way to build a motor, but I do not believe it is required.

 

Alright then... I think I get it... Everything is S4 turbo so I think I will be alright....

 

If you want absolute true balancing, then you could have the rotating assembly balanced. You would need to send out the rotors, e-shaft, counterweight and flywheel to have it done. Lots of engine builders swap shafts, rotors etc. such as s5 rotors and counterweight on s4 keg, etc. If you were to regularly push 10k rpms on a race car, it might justify the extra cost, otherwise not in my opinion. Keep in mind the s4 and s5 flywheels are different, so use same-series as the rotors and weights.