The '87 model GSXR1100 uses the 1052cc engine instead of the 1127cc engine of the '89 and later. The 1052 motor is in the same family as the other air/oil cooled motors, but it's a little different from the 1127/1157 big bores and appears to be more closely related to the 750. While I'm pretty sure the whole head would swap (since the 750 heads will), I'm not certain the valve cover would. I'd also be concerned about the lack of a breather. (Or does it have one and it's just different?) If the 1052 isn't breathing thru the cover, it's breathing somewhere else and to use this cover on the B12 would prevent it from breathing. A bad thing!