You didn't mention if you found any foreign matter in the rear float bowl chamber or the needle and seat. My thought on the front carb acting up is, it has now picked up some crud like the back one. I'd start by cleaning the float chamber in the front carb, reset the floats to the recommended level, reset the nozzles to 2 1/2 turns down, use a Uni-Syn to balance the carbs. As it's been running kinda poorly, I'd also change the plugs, and reset the valve clearance too. Basically, a complete tune-up to eliminate any other possibilities. It's also possible that the nozzles are sticking in the down position when the choke is off. With the choke lever off, reach under the carbs and push up on the nozzles. If you feel the nozzles move up, lube the outside of them with some lithium grease. It may start better, for now, by using no choke and part to full throttle to compensate for the extra gas.