As a teenager I was finishing a painstaking re-assembly of a Villiers 2T two-stroke twin and was about to mount the cylinders when I dropped a circlip into the crankcase. Horror! Take it all to bits again! Crikey! (or similar)
My dad said “ the crank cheeks in a two stroke have to be a close fit in the crankcase to force the necessary gas flow. Turn the engine by hand until the crank cheek appears in the cylinder hole beside the conrod, and put a glob of stiff grease on the cheek. Then slowly turn the engine 360 deg until the crank cheek reappears, the circlip will be stuck in the grease