Hi Paul,

The 9.7:1 rotors are considerably lighter than the 9.4:1 units.  If you are going to use 9.7:1 units,  then the best option is to just get the whole rotating mass re-balanced.  You can use the eccentric shaft and both the counterweights you already have. It is always better to start with counterweights that are too heavy,  rather than try to add weight to too light counterweights

The Balancier will first dynamically balance the lighter rotor of the pair,  and match balance both rotors to the same weight.  Then balance the whole rotating assy by just removing material from the counterweights by drilling/grinding to get the balance cortrect. This will give you a superbly smooth motor.  .

WARNING:  If you try swapping counterweights, it's fraught with pitfalls,  and you never really know you have the correct counterweights until you run the engine (unless the assy has been scrupulously kept together - the older shafts used to have correspondence numbers stamped on the so you could tell if they had been swapped).  You will need both the front & rear Series V '89 -91 counter weights,  which don't have any distinguishing part #s or identification marks on them.  A nightmare even if you are experienced.

Re-balancing is ALWAYS the best option.  What it costs you to have the whole assembly dynamically balanced,  you will save some if not all by NOT buying or scrounging additional counter weights.  Additionally,  you are guaranteed to have a perfectly smooth engine.  One has to experience a really good balance job to appreciate just how smooth Mr Wankel's Wonderful Whirrler is!  Factory motors,  while usually pretty good balance-wise,  are balanced to a tolerance,  and are often not as smooth as they can be.  Like I said,  you have to have experienced it to understand!!  Take the time and the extra bux to do it once and do it RIGHT!

Cheers,

Leon