90-percent of crank breakage in the front half of the engine is due to a balancer that is too large in diameter, too heavy, has moving parts, and cannot be balanced with the crankshaft. Moving parts include both fluid and mechanical pieces. These dampers cannot react fast enough to rapid acceleration and deceleration. Therefore, they create harmonics that will eventually fatigue a crank and break it. These dampers were designed for industrial applications that run constant speed in narrow RPM ranges. So, that being said, the smallest diameter, lightest weight, and an elastomer design is best.
