Hi I just got in the lens for parts. The lever that controlled the aperture was completely stuck (Its the lever the camera uses to stop down when taking a photo). I removed the mount and moved the aperture lever back and forward till it moved. It feels dry but I'm not sure. Anyways, now The blades open perfectly when I set it wide open. They close down when I stop it down and manually move the lever, but they do not spring open as they should. There is no oil on the blades. They look new. Everything on the lens looks great. Any idea on what is causing this? Thanks for your help folks.