The Hildebrand & Wolfmüller motorcycle is generally considered the first production motorcycle, with production kicking off in 1894.
There seem to be at least a couple still in operable condition, and a handful left in any condition. The rear axle is the crankshaft. There is no clutch. You push off to get it going, and you kill it to stop. The engine is watercooled, and while there is no radiator, the rear fender is an extra large water tank to keep things cool. You have to love an engine that gives about 5 or 6 chugs per telegraph pole. I don’t know what kind of torque this puts out, but considering it revs up to less than half of what a modern engine idles at and there is no horsepower to speak of, it must have a lot to give to keep this thing moving fast enough to maintain balance.
Here’s one I stumbled upon by chance at an airplane museum in Germany about 15 years ago. The frame is very interesting in that it bears no resemblance to the safety bicycle style diamond frame later motorcycles would be based off. The front brake acts on the tire, and the rear wheel is small to allow the engine to rev up to a screaming 250rpm. You can also see a crank with a wood handle up by the head tube. That - believe it or not - is used to adjust the tension of the rubber bands which pull the pistons back up to top dead center. Rubber band tensioning is one thing modern bikes just never seem to get right.