not sure what is going on....

My name is gabriel and i just started on this forum because i bought a 1979 kaw kz400 last year. great looking bike with 95% orignal parts. i bought it for less than 500 dollars and had the whole electrical looked over and repaired. now here is the question...i'm not sure what is going on here but i had cleaned the carb with a carb cleaning spray, pitcock and gas tank. i got the bike started and drove it for about 10 mins. it ran ruff the whole time. i bought a carb cleaner for the gas tank. i drove it for about 20 mins the next time and it ran great. today i got on it and got down the street and started to pop nad seemed to be back firing. then the bike died... got it started again and then it died again. but is this the carb that is doing this or what? any help would be great. thanks.

is it getting fuel? might of knocked some crud loose in tank

well i did a rust remover on the tank. got it cleaned up pretty good. but like i said it was backfiring or whatever it was doing befored it died.

Probably broke rust loose and plugged up the carbs with it. That will make it act like it's lean and when gummed up enough, prevent it from running at all. Tear the carb off and clean and pull the petcock off the tank and clean it and the tank out might take a couple tries to get all the shit out but you can do it. If you use water to flush the tank be sure to rinse that baby out with rubbing alcohol to evaporate any water in the tank

maybe install an inline filter to catch future crud

Welcome to the madness, Gabriel.

The KZ400 is a neat bike and fun to ride when everything is working. Several things, including carbs, can cause the symptoms you describe. Search the filebase of the forum for Carbs 101. It is a detailed description of how to properly clean and make preliminary adjustments to the carbs. An inline filter is a must. Spray cleaner will not get the job done.
You also need to check for air leaks, particularly around the intake manifolds. They get hard and leaky as they age.
The ignition also needs to be in top shape, from battery to spark plugs and everything in between. Search the forum or beg MFolks to post his approach to electrical system diagnostics.
Patient, systematic diagnosis will eventually lead to bike nirvana. Help from the forum and large quantities of adult beverages will also help.