Obviously emissions ended them. But 20 years ago Bimota brought out a 2-stroke bike that used fuel injection. Fuel wan't injected until the exhaust port closed so it didn't spew out the exhaust pipe unburned. Ran very clean & got great fuel mileage. They said a 500 twin would make 100+ hp but weigh like a 400. Well, Bimota had problems with programming, never got it right & almost went out of business. Or did & came back. Snowmobiles & personal watercraft has been using this technology 20+ years but somehow it can't be applied to motorcycles. My guess is that no one wants to roll the dice & risk going bankrupt developing a 2-stroke bike that may or may not sell. Me, I 'd love a liquid-cooled RD400. They vanished about the time I got my license to ride.