No. An inline motor is inherently balanced, so as long as the pistons are balanced, the rods are balanced, the crank is balanced, the balancer, clutch, etc, you don't have to rebalance when you change components. On a v-motor of any type, the 90 degree twist means you can never truly balance the motor for all rpm's, but they can use bob-weights to approximate the forces acting on the crank to minimize the vibrations in the rpm range you are primarily using the engine in. A good shop will find out what you are doing with the engine and balance it to suit on a V-6/V-8. Score one for the inlines!
