This 12-minute FortNine video regarding obscure motorcycle engines is worth watching. The Sears "twingle" is mentioned. I would look at Sears (Puch 175-250cc) motorcycles in their catalogs for many years and always wondered what a "twingle" was. It was only many years later that I found out how the engine worked:
Current motorcycle collection: 2002 Yamaha FZ1; 2020 KTM 390 Duke; 2009 BMW F650GS; 2018 Zero S 16.6 kWh