David Windhorst wrote:

Not to mention 2-cycle racing motorcycles. I have great smell-memories
of attending bike races in my early teens, when the sport was less
stratified, and more grass-roots, run-what-ya-brung. Sitting around an
abandoned quarry turned into a scrambles track, bikes (many converted
from street use) from five or six different displacement classes
screaming around in circles under a cloud of sweet-fragrance blue
smoke...not very environmentally friendly, but a spectacle I'm glad to
have witnessed.

Although I have a 4-stroke behind me when I fly nowadays,
2-strokes have evolved into extraordinarily reliable engines
and I've accumulated more than 1,500 hrs. flying aircraft
equipped with "grassroot" 2-stroke engines. We normally
premix the oil 50:1 (not Castor oil) but except when starting
after a prolonged period of inactivity, they rarely emit the
characteristic blue 2-cycle smoke anymore. Given their
impressive power-to-rate ratio, 2-cycles are ideal for light sport
A/C. For example, in 1993 an intrepid Alaskan pilot flew a 2-stroke
over Mt. McKinley's 20,320 ft. summit, and on Sept. 29, 2000, Czech
pilot Jan Bem set a world altitude record of 26,546 ft. overflying
the peak of Annapurna, Nepal, in the Himalaya Mountains while
flying a 2-stroke powered trike. The U.S. military still uses 2-cycle
engines on numerous different remotely-controlled surveillance
drones.