I’ve got a 1978 GL1000. I bought a rear master cylinder kit for this year, but when I took the master cylinder apart the piston is different. The old one has a rubber “boot” on the piston but the one on the rebuild kit does not. I’ve noticed that the 75-77 rebuild kits do have it. Am I mistaken that the rebuild kit I have isn’t right, and maybe an older master cylinder was installed/swapped onto my bike?