Vacuum piston return spring

Also known as a vacuum valve spring, a carb spring, a slide spring, a diaphragm spring... You get the idea. This is the spring that helps push the carburetor's vacuum slide back down when you let off the throttle.

If you need one, either the previous owner cut your original springs thinking that was a "go fast" upgrade, or else someone goofed and bent one up. So it goes.

Just generically speaking, this is for Keihin CVK carburetors. Based on the photos I can find, this is NOT the same as the one in the Kawasaki KLX250S. Ural's spring has fewer coils.