1982 cm450c idle problem

ok so i got a1982 cm450c that i've been rebuilding the last 6 months. I've rebuilt the carburetors completely with all new parts. i have good compression. The bike idles fine on the right cylinder but not the left. If i got to 3000 rpm or beyond it seems to run fine. The carburetors are synchronized. I have been trouble shooting this problem for a week now. At idle i get backfires and slight stalls from the left cylinder. But not on the right one. After extensive work on the carburetors i don't think there is much i can do. so i am leaning more towards an electrical system problem. i've checked al connections and thy seem to be good. i've used two different sets of new plugs and i get spark form both. using the honda factory manual i checked the ohm measurements for the alternator and they are well within range. but as for the cdi module the measurements i got were out of range, instead of getting 10-30 ohms on certain connections i was getting between 6-800 ohms. which is way higher than they should be. So i believe its the cdi. But when i swapped the plug wires, left <-> right, the same problem still occurred. and now im stuck. Has anyone had a similar problem? also if this does seem like a cdi problem does anyone know where to get one, this is a very rare part from what i am seeing. and i cant seem to find anykind of workaround for it. thanks!