A stuffed crank ups the "pre-charge", and thus the effective final compression ratio. Higher compression = more low end power. And if you have a stuffed crank you will notice the difference. My aprilia has a stuffed crank and it is night and day.
please also remember that stuff you"do" to motorcycles (4 stroke) dose not normally relate to 2 strokes. By reducing rotating mass your engine builds rpm's faster so lightweight is great but the crank is not where you loose weight on a 2 stroke. Lighter magneto assemblies & lightened gears are the place to look.