Performance Flywheels

The standard flywheel on a PX weighs 2200 gms. One of the standard tuning techniques for Vespas is to use a lightened flywheel -- this reduces the workload on the crankshaft, which in turn leads to higher revs earlier on and is thus of great advantage for taking off and accelerating hard. The process of lightening the flywheel can be achieved by cutting out some of the unnecessary metal (pictures 1 & 2) or by manufacturing the flywheel out of nylon or similar material (pictures 3-5). The weights of lightened flywheels range between 1000 -1500 gms. Generally speaking, however, lightened flywheels are not recommended for touring where a heavier flywheel is more desirable because of the greater momentum generated. It is also worth noting that some lightened flywheels have smaller fins and therefore their cooling capacity can be considerably reduced. Caveat emptor!

Another thing to investigate is if changing the balance between the flywheel and clutch (either side of the crank) may unbalance the clutch leading to rivets popping. Or perhaps the acceleration force is transferred more to the clutch than before. No concrete evidence yet but something to think about if your clutch breaks after fitting a lightened flywheel.