69_340_GTS said

As Murray said, you pulled the piston out of the m/c. The pushrod will come out of the piston if you pull it hard enough. There is a small o-ring on the pushrod that just pops into a recess iside the piston, The o-rings get hard and sometimes hold the pushrod in tight. Maybe don't bother with the old stuff... I'd buy a 4-hole to 2-hole m/c adapter, an adjustable pushrod, and a modern aluminum m/c from someone like Dr. Diff. DoctorDiff Drivetrain Components

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Murray said

Pushrod is attached to the piston by a square "O" ring inside. Put the rod in a vise with the piston sticking out and I use two screwdrivers to pry the piston off the rod. It is held in place very tightly so so will need some force. You will need another "O" ring to re-install. See if your new M/C is the same set-up.

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