You should be able to just knock that part right out like Stuart said, they heat them and press them in when new. To install the new ones, make a fixture out of some heavy metal to hold the rivit head when you beat on the new ones. I used a round headed carbide cutter in a heavy piece of 2"x2"x2" steel and just cut a halve round hole big enough for the rivit head to fit in. Then I installed the rivit, clamp, and spring, next I heated the rivit stem red hot and with a 5lb hammer smashed it in place. It was real easy to do, I also heated the spring clamps when I bent them over the spring pack. Joe
