Everything between the engine and the back wheel on an automatic scooter: the belt, the roller weights, the clutch shoes, the springs and the bearings.
A belt on a machine used daily in Malé traffic wants changing somewhere around eighteen to twenty four thousand kilometres, and rollers roughly every second belt. Anybody who tells you every eight thousand is selling belts.
The symptom worth knowing is a machine that pulls away fine but will not hold speed on the bridge. That is usually a worn belt or flattened rollers rather than an engine problem, and it is a cheap fix caught early and a clutch job caught late.
We sell roller weights in sets and in single grammes so a mechanic can tune the pickup for a heavy rider or a load. Come in and ask for the weight rather than ordering by the picture.