What condition is the body in?
It starts with the classic: the sheet steel skeleton under the duroplast body tends to rust. This skeleton was driven from one production site in Zwickau to the other on open trucks in wind and weather. Right from the start this is, shall we say, suboptimal.
Has the engine been properly maintained?
Does the gearbox make noise?
The fourth gear freewheel must engage and disengage evenly when you take your foot off the accelerator. Ultimately, the gearbox should be tight.