Here's a restored 1969 Ossa Pioneer. I had one back in the day. Spanish bike. It had solid state ignition, the only bike I saw at that time without points, a fiberglass body, Telesco front end, ball bearing crankshaft, roller and needle bearing in the crank, compression release for keeping revs up in turns, and removable chrome muffler. I bought it used and later found out it had been laid over shearing off part of the shifter shaft. After time the shifter would come loose and I'd have to re-tighten it. I tried a bigger bolt, shims, putting a nut on the bolt, even tried welding onto the shaft to extend it. Nothing worked. Finally decided to split the case and get a new shaft. At the time I worked at a Yamaha shop so I had access to a flywheel puller. Stripped three of those suckers trying to get that flywheel to pop, even used an oxyacetylene torch to heat it and pound on the puller. Finally threw it under a bench and walked away for a couple days. Came back and it was free! Had it bored three over while it was apart. Darn thing was indestructible and one of the best handling bikes of that age. I could out run 360 Yamahas by literally miles.
Ariel square 4 was the first time I heard a 4 cylinder motorcycle engine. I loved the sound and the idea of them.