I don't know much about GT750s, but before you get into compression seals and such, you might try: 1) Clogged, dirty old air filter. This could be marginal, allowing OK air for idle but not enough at higher throttle. 2) Bad spark plugs? Who knows why this might cause you condition, but they are easy to check and cheap to replace. 3) Clogged fuel filter or gastank vent? 4) Main jet in carbs could be clogged up with some jelled gasoline. 5) Check out the ignition timing. Good luck and let us know.