700cc versions of the GSX750E and GSX750ES were special made
for the USA market. For some reason the GSX750-series couldn't
be sold in the United States in the mid-eighties unless the
piston replacement was reduced to under 700cc.
A reader from USA told me this: I worked for a
Suzuki dealer from 1983 to 1986 and from what I was told by
the shop owner the import taxes were changed after 1984. Over
700cc bikes were much more expensive from that point on to import
and the factories dropped the displacement from 750 to 700 to
keep the bikes from being too expensive.
Willy, the shop owner, called them them »no change»
models, as in $7.50 compared to $7.00.
Another reader could tell us something more about the American-only 700cc models from 1984 to about 1987: The reason why president Reagan approved steep import duties was to protect Harley Davidson while they struggled out of bankruptcy. The duties applied to all import motorcycles 750cc and over. Only USA was involved, for example Canada did not have such a tariff.
As for the other members of the four-valve GSX family, the model
was called GS in USA. Therefore the models were called GS700E
(the naked version) and GS700 ES (with bikini fairing).
I don't have much to tell about these models yet but here's
a picture of a GS700E to start with: