It makes a huge difference..if the carbs are truly clean and you have a stock airbox on it,it should start and run on the choke but thats about it..
those bikes run REALLY lean(to pass emmisions at the time)and removing the airbox or filter really aggravates the situation..
You MIGHT could get it to work ok with a jet kit with those pod filters but if its all stock running the airbox is the way to go..
I had also seen people stuff rags under the seat(for what reason im not sure,maybe they just liked having a rag handy) but it ended up blocking off the air intake..once saw a KZ440 that had sucked the rag into the intake and it got stuck under the intake valve..which was actually pretty humorous(to me anyway)...
oh yeah one more thing i just thought of....on the carburetors,theres a hose running off of one of the carbs to the vacuum fitting on the fuel petcock...if its not hooked up,or plugged off,you will have a massive air leak to that one carb which will make the bike run like doo doo..are there little rubber caps on 3 of the carbs covering the tubes you hook up to to synchronize the carburetors?Or one hose that connects all 4 carbs together with little *t* fittings?(THe 4th one will have a black hose that goes to the gas tank petcock,it supplies vacuum to the petcock to make it open in the *on* and Reserve* positions..
When the petcock is in the*Prime* position it allows fuel to flow freely,but will run the tank dry if you ride it that way.
What im getting at is if any of those vacuum fittings are missing it will have a air leak and run bad or not at all..
So check those vacuum fittings on the carbs...
If you go one You Tube and type in *KZ750 carburetors rebuild* or something to that effect theres some videos i think..i learn all sorts of stuff from You Tube..