hey I have one of these too, see http://auction.netbikes.com.au/vjmw.php ... page=kz750
Done a stack of work after these pics were taken, it is almost finished now, I will update the page in the near future.
I had the same carb spitting problem you have/had. I ended up replacing all the float needles and the float height is critical on this bike, you have to get it just right. The motor seems to be running and reving fine now but I have not ridden it yet so under load test still to be done.