I have done this to all of my machines, as others have suggested, rebuild the the pops. I clean all parts, sand plungers starting with 800, 1000, 1500, 2000. Does not take that long, but when dealing with 5 pops it can feel like it. Order all new parts for the pop (except the cap) New springs from PBR also help. Don't forget to order new light sockets. My rebuild pops on my '64 River Boat blow people away on play factor. Don't rush a restoration. You will be happy in the end.