Working loose an exhaust pipe from a Vespa scooter engine cylinder only involves a few steps. But they must be followed in order or the job can become frustrating and more difficult.
Use a socket wrench and 15mm metric socket to loosen the securing bolt that attaches the exhaust to the engine swing arm. Unscrew the bolt completely and put it aside for a moment (the exhaust will remaind attached to the engine).
Take the same socket wrench and a 13mm socket a loosen the clamp bolt holding the top of the exhaust to the cylinder downspout. Loosen it but don't remove it.
Position a 1-by-2-inch piece of solid wood between the cylinder and floorboard so the end of it sits on the exhaust pipe arm leading to the cylinder. Hammer the top of the wood (not the pipe itself) until the exhaust pipe comes off the cylinder.
Locate the exhaust pipe end that connects to the engine cylinder (visible with two bolts that hold it on). Use 10mm crescent wrench to loose these bolt nuts.
Use an Allen wrench to loosen and remove the rear exhaust bolts holding the pipe to the engine underneath and behind the flywheel fan.
Pull the muffler off and clear of the scooter once all the connections are removed. Let the exhaust's weight help you pull or drop it off the engine.
If you can't find a piece of wood to hammer the vintage exhaust loose, then use the handle end of a hammer or rubber mallet. Place the head upward and hit it while the handle sits on the pipe itself. Using wood will prevent the metal pipe from getting dented by the impact.
Do not work on the Vespa exhaust after the engine has just been running. You can easily get burnt.