Slow speeds not smooth 1981 KZ 440

I have recently cleanned the carbs on this bike. It wasn't running before the carb cleaning. It starts easy and runs good except for low speeds. Trying to maintain a constant speed of 30 mph or less (1/4 throttle or less) it sounds like I am popping corn.

Acceleration is good (no backfiring) and higher speeds are good.

Does this sound like the pilot system is still in need of attention. Pilot screw are turned out 1 1/2 turns.

Thanks in advance

Hows the sycronization of the carbs?

I did try to sync the carbs using a home made thing. (A 10 foot clear tube wrapped around a yard stick with oil in the tube and makeing sure that both carbs were pulling the same vaccum. Found this method on the net)
Short answer - I think the carbs are synced

With my kz400, getting the carbs synched did a world of good. Also, I found that if I didn't pull the pilot screws when I cleaned the carbs, I couldn't really get those passages blown out with air after I hit them with carb cleaner.