I finally got my 85 Vespa Si, and it got a clacking sound in the rear when accelerating under load (with my weight on it). It also struggles with getting going, like something is holding it back.
When it sits on the center stand with rear wheel in the air, it accelerates smooth and without noises.
It had this noise when I bought it aswell, but i figured it would dissapear after rebuilding the transmission with new bearings and stuff. It didn’t..
It is a variated SI, with stock variators front and rear. Clutch and all parts in driveline are stock.