Regular piston engines are balanced so the numerous moving parts don't create too much vibration. This is usually accomplished by strategically weighting moving parts and/or timing cylinders to fire in such a way that they cancel each others momentum as much as possible. Clearly this is well done in modern piston engine vehicles, as most of them run fairly smoothly.
How are rotary engines balanced? Are they inherently balanced since there is really only one moving mass? Do they have balancer shafts like some 4 cylinder engines do?
I'm interested specifically in things with 4 wheels, but answers for motorcycle rotary engines are also interesting