For the do-it-yourself mechanic who enjoys scooters, the Vespa scooter provides the most straightforward environment to practice full mechanical repair. This is because the rotary, two-stroke engine design allows a simple rebuilding process that most amateur mechanics can understand, and it requires only a few speciality tools.
Disconnect the engine from the scooter by unhooking all electrical connections, detaching the fuel line using a screwdriver, and releasing the cables with a cable snipper. Use a socket wrench and crescent wrench to loosen the swing arm bolt and the rear suspension bolt. Remove the bolts and pick up the engine to place it on a work bench.
Remove the rear tire and rear hub with the socket wrench. Remove all engine dust covers with a screwdriver. Place removed small parts in a metal pan for safekeeping. Turn the engine around and loosen the flywheel with the flywheel puller after wrenching the axle nut off while holding the flywheel fan with the holder tool. Use the socket wrench to then loosen and remove the exhaust pipe and the gear box controller on the bottom.
Use the socket wrench to loosen the cylinder cap and cylinder. Carefully slide the cylinder off, over the piston. Stuff a rag in the cavity so the piston doesn't bang around. Use a socket wrench and crescent wrenches to remove all engine case bolts. Remove the clutch side cover. Use the clutch nut tool and holder to loosen and remove the clutch.
Tap the engine cases with a rubber mallet until they are loose enough to spread and pull apart. Pull out the gears and axle using hands, a tap, and a hammer. Carefully tap the crankshaft out of the main bearing in the engine case. Make sure it doesn't drop on the table or ground. Remove all old gaskets, bearings, and oil seals until the cases are bare.
Wash the bare engine case halves with kerosene or similar solvent. Do the same for all the engine parts except the clutch and crankshaft. Let them dry in open air until the fumes are gone. Place new engine bearings (clutch side, flywheel side, rear wheel) in the freezer.
Use a hand burner to heat up the area where the bearings would install. Heat up the outer ring and then quickly grab the frozen bearings and tap them nto place with a hammer and appropriate side socket. Do this for each bearing. Place the oil seal and tap it into place next to the bearing. Secure them with engine circlips previously removed. Tap the crankshaft into the main bearing centre until it is seated. Tap the main transmission gear into place next with a punch and hammer.
Install the clutch onto the crankshaft arm and tighten it down with the clutch nut tool and holder. Turn the engine around and reinstall the axle and lower transmission gear set. Apply the engine case gasket between the halves. Take the flywheel side and install the kickstart gear and spring by hand. Place the actuator gear for the kickstart on the main transmission axle and close up the halves. Tap them shut with a rubber mallet. Tighten the engine case halves with all the engine case bolts and nuts and a socket wrench.
Place a new cylinder gasket on the cylinder side of the engine. Slide the cylinder over the piston and into place after greasing it with engine oil. Place the cylinder cap over the piston face and close it up, securing the nuts diagonally with a socket wrench. Use the socket wrench to also secure and tighten the gearbox controller. Lastly reinstall the clutch side cover with new a new o-ring seal.
Re-install the rear wheel hub. Bolt it down with a socket wrench. Connect the rear wheel with the same tool. Use a screwdriver to reattach all the engine dust covers. Bolt the completed engine back into the scooter via the swingarm and rear suspension. Re-connect the electrical connections and hook up the fuel line to the carburettor. Insert new control cables and attach them to the engine. Turn on the engine and take the scooter for a test ride.
Using owner workshop manuals can be very helpful since many publications provide step-by-step directions on how to perform a Vespa scooter engine rebuild.
Never force a part to come off or tighten with brute force and a metal tool. The engine cases are made of aluminium which can warp, dent, or crack under pressure from a steel tool.