Not running good

When my 75 KZ400 is at and idle the right side exhaust is making a popping sound, and doesn't run right at cruising speed. it cuts out pretty bad, it also does it when I get on the gas pretty hard. Then the left side spark plug is black, but the right side looks almost perfect and they wre brand new plugs. What do I need to do???

Need a little more info. When was the last time the bike ran well; did this problem just start? Did the bike sit unused for an extended period prior to this problem? The reason I ask is it could just be a dirty carb if the bike ran ok the last time it was used on a regular basis. Ed

Well you say nothing about checking anything yet?
Start with spark, are you still running points?
If good, take the drain screw out of the carb with a funnel under the hole to a catch clean container, and then put the petcock at PRIME. Let the fuel flow over the needle and seat for a bit, then turn it off. Now you will see if gunk is in the bowl/ and you will have rinsed the needle and seat.
Do you run a fuel filter?
Have you got a compression tester?
You may need to rebuild your carb's, as the fuel circuits could be plugged, very common. But also check for vacuum leaks at the intake manifolds.

Does sound like carb problems. Always first thing is drain and rinse the tank, clean the petcock assembly, drain clean fuel dwon through the carb drains, and run some cleaner in the system. Inline filters always a must.

I had the bike given to me in october, and the last time it had a license plate sticker on it was 1986....so yes it's been sitting a long time. The guy that gave it to me said the carbs were dirty so he cleaned them up. I have inline fuel filters but they didn't seem to be filling up with fuel so I took them off. There was some rust in the tank but I got a lot of it out. I've pladed with the fuel air mixture and the float because it was pouring out of the overflow. I don't have any of the tools that would be required to test compression or vacuum. I adjusted the points and timing so that should be good now. It idles fine but once it gets on the road it's not smooth at all. The previous owner cut off the megaphones b/c they were rusted out. I put some internal baffles in. Would it help if I got some of the packing to go around the baffles?

Without a doubt you need to clean the carbs and put the fuel filter back on. Ed

Dont bother with the exhaust, focus on those carbs.

1st: Get a manual, you need it. Bikes require lots of maintenece and patience.

Do everything listed in the maintenence chapter.

GL.