Hello from a 3 wheeled scooter and its not an MP3 type

Hi all, we have a BOOM Fun 500 trike that has a Piaggio 500cc single engine and auto drive train.

Recently it has started to knock and chug when pulling away slowely. Its a real pain in traffic.

Anyone any idea what may be wrong?

I had a variator to bits, changed one of the belt discs (not sure of correct name), the belt, all the bearings, pully fan and most of the spacers.

It seems to be getting worse and we are worried it will damage the drive system.

Any ideas?