75 cb750k front brake problems

[Bowiesport]

I bought this nice 1975 cb750k that had been sitting for some twenty plus years. the front brake was disconnected / no master cylinder but everything else was still there. The front pads weren't sticking and looked to be in good shape. took everything apart and cleaned the piston ect. put it back together and even with pads all correct , and little dome in place on piston side, no clearance for it to slip over disk.Its pretty simple system but i am stumped?? will the old pads swell if oil or age. they don't look much different than new ones i look at??? Seems something is amiss.any thoughts or has any one else had this issue.

 

[tommycarl]

Pictures might be helpful... are you sure the piston is in as far as it will go?

 

[Bowiesport]

Yes its all the way in and i measured it with my calipers . Its flush with the body. It seems its the fixed side that seem too thick. I don't know, am going to buy new pads and see.