Re-Instatement of 83 GSX750 EZ from a 7/11 to a 750 & creating a new 1100

[Grimly]

So i finally got around to doing compresion test. 70 -75 all round so thats not good. I have pulled the head and block off and will do some measuring to see which direction i head. There is nothing obvious like broken rings to explain the lack of compression.
Any suggestions on likely issues?

If the ring packs are not stuck and the bores look ok (measured up ok?), then it may be overheated rings at some time in its history. Happened to me once, spent the hottest day of the year in London traffic all day long and next morning the bloody thing wouldn't start. Compressions were almost zero. Taking it apart revealed nothing visibly wrong, but my major suspicion was on the rings given the immediately prior running condition.