Welcome to the Pentax Forums!
Do you have a manual for your camera? Most SLR cameras are designed for the lens to remain full open until the shutter is released or DOF preview is engaged. There is usually a coupling lever in the mount to enforce this rule and to allow the aperture to stop-down to the set value on the lens or the value set by the body (depending on mode).
The manual is available for download at the Butkus site for free, though he does appreciate a donation
Yashica FX-103 Program user manual, instruction manual
Steve