Complex sentence: If the pistons could lie on the same crank rotational plane, then the design is inherently balanced for the momentum of the pistons, but since they cannot, the design, despite having a perfect 3.
Split into simpler sentences: If the pistons could lie on the same crank rotational plane, then the design is inherently balanced for the momentum of the pistons. But since they cannot, the design, despite having a perfect 3.