So why does a 9.5lb flywhjeel need a counter weight, doe sit have something to do with the inertia? Other than you need to slap it on the flywheel to actually mount it to the engine..

 

The original flywheel has a built-in counterweight.
Aftermareket flywheels don't, you will have to buy a counterweight from an automatic.
The rotary needs counterweights in each end to balance it out...

^^^ that is put in the most basic way

 

I see...so it pretty much is just balance and the fact that and the flywheel needs it.

 

The flywheel doesn't need a counterweight, the rotors do.

 

Get your Counter weight from:
Ray of Malloy Woodbridge
1(888) 533-3400
They give a substanial discount to RX7 Club
and shipping is free. Its about $ 123.00