No Air fIlters in stock air box

I just got my 1979 kz1000 ST shafty I plan on rebuilding the carbs and having them balanced. I noticed there was no air cleaners in the stock air box. How would this effect how the bike acts besides the fact its letting all the dirt and grime in of course? The bike starts right up right now but is boggy and backfires when you rev it up. It sounds like its running on all four but will check the plugs ASAP. I know I need to start widdling down allot of factors. The bike is breathing thru the air box, would installing air cleaners make it act any different?

Thanks for your help I'm just getting started on this project. I'm looking forward to diving in and seeing how this baby ticks! Any sujjestions on repair manuals?

You need an air filter in that box, to clean the air and it will of course restrict slightly the amount of air entering the carbs. Don't think it will make much difference though with your problems.

Mine's got a K&N shoved down in that slot. Definitely need to use some kind of filter.

Just more info.
On my 750, if I remove the air filter when running at idle (~1100rpm), the bike will idle up due to leaning the mixture out. You want an air filter in there before adjusting the carbs. Good luck.