Aprilia are known for shitting cranks, You may have had a good run I have replaced 5 cranks for people in these bikes. There was a few engines in these scooters
The morini was crap the mineralli engine was alot better. You may have had the mineralli one as most of the morni ones are on there 3rd crank
Roller weights too light no top speed, to heavy slow speed
just right fast acceleration as well as the same top speed.