The trick, for lack of a better word, to removing and properly installing cotter pins is to use a press to do so. I made this small press out of a couple of nuts, a high tensile set screw and a piece of 3/4 key stock. It ain't fancy but it works like a charm.
Removal: remove cotter pin nut and flat washer. Install cotter pin press, threaded set screw pressing on the threaded end of the cotter pin. Tighten up the set screw on the press (do not go crazy - just make it good and snug). Lightly tap the square end of the set screw and feel for looseness. Snug the screw up again, tap and check until the cotter pin slides out. NOTE: This is not guaranteed. Sometimes the pins are just too tight.
Installation: slide cotter pin into crank arm and spindle flat. Install cotter pin press, threaded set screw pressing on the head, not the threaded end, of the pin. Snug up real good and give the square end of the set screw a couple of taps with a metal hammer. Snug and repeat several times. Once satisfied that the pin is good and tight, install the cotter pin flat washer and cotter pin nut. Snug the nut up in accordance with appropriate torque values and you are done. Note: Be careful with hammer impact. Too hard and too much might dent bottom bracket bearing races.
Hope this was a help.
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