is there a way to test these motors while they are out of the car?

Can we do a compression check on the rotaries when their out if the car?

 

Yes, you can. however you will have to set up some sort of test rig to get the starter engaged to the flywheel and then apply power to the starter. The easiest method is if you simply mount the transmission to the engine, and then the starter to the transmission, and have that whole assembly anchored somewhere securely.