I get ask all the time from people who just bought a vintage bike and thought it might be helpful if I would throw together a list of parts that are nice and cheap to have around when owing an old scooter. In fact I always have at least a set or two for these parts just in case. Also, be sure to know what motor you have your scooter first. Here goes....
manual
engine seals
engine gasket set
clutch plates/springs and NEW clutch nut. (soak corks in 30w overnight)
points and condenser (if you have them)
carb gastet kit make sure to ask for the float and needle
small end bearing and rings
shifting cross (Be sure to tell what year motor you have when ordering)
fuel tap and fuel hose
All this stuff is pretty cheap (maybe around $150 to $200), but it's usually enough to give your new old scoot a basic engine rebuild.
Also, ALWAYS have a set of inner cables especially the shifter and clutch ones and pinch bolts. Well, these are the most common things I have seen that get replaced. Things like bearings, pistons, brake shoes tire etc I order when needed to save money.
Must have specialty Vespa tools are as follows...
clutch nut tool
clutch holding tool
flywheel puller
flywheel holder
forth hand tool
fuel tap wrench
All these tools might be around $100 or so at places like Scooter Works. Also, very helpful is a NEW C.D.I. and pickup box to test the old one with.
Not cheap but worth every penny is a motorcycle lift. Around $300.00 at Harbor Fright.
And of course always have a set of tubes and headlight bulbs around for good luck because when you don't have them that's when you need them the most.