Left side engine and exhaust weak/not firing

So I bought a 1976 kz750b1 about a month ago for about 600$. It wasn't running very well so I did a complete carb rebuild and put a new battery and new fuel lines in. It ran great for about a weak when all of a sudden the left side of the engine seemed to just stop. So I took apart the carbs and cleaned them again and got a solid 6 hours of straight riding all day and then the same thing started happening again. Symptoms are that the right side seams to be doing all the work when there is a load on. The bike bogs really bad at about 4000 rpm in any gear, left exhaust weak and sputters and it will die when I'm riding off after being at a complete stop. Any suggestions or know what I should check?

Is there a clean inline fuel filter?
Fuel level in the carbs checked using the clear tube method?
High tension lead and cap checked for breaks, cracks and proper continuity?
Valve clearances in spec?

Were the fuel tank, filter screen and petcock carefully cleaned? There could be lots of dirt, water, rust, sludge, rocks, sticks, and dead mammals in there that are continuing to clog up yer pretty carburetors.

Fuel line filters are in use and brand new, as far as the other things you mentioned, I'm not sure. This is my first prefect bike

And I did clean the peacock but I don't think that's the problem since my right carb is doing great

One coil has gone out or is going out intermittent?

Havent even thought of the coil going bad. But it seems like that could be a problem since it's only the left side acting up. And the carbs seem to be perfect. I rode just fine all day for a good 3 hours until the last 15 minutes of riding. New ignition could will be the next thing to fix on the bike. Thanks!