2 days ago, only 1 cylinder firing, yesterday BOTH, today just 1 again. (SOLVED)

i've just got a 1986 yamaha virago 700. It's got spark and compression.. i put in new plugs, and i cleaned out the carbs (perhaps not enough) then reset the mixtures until it was idling.. on only one cylinder. which is how it was before.
yesterday i pulled the plugs out, let them dry, rubbed them with a wire brush, then checked for spark, i had it on both, i cleaned the connections at the coils with electric cleaner and a little file. i checked the igition wire to the plug for the cylinder that wasnt firing.. there was some electric tape on it. i took it off and found a little slice in the outer rubber insulation that looked like it got pinched by the fuel tank. it didnt go deep enough to penetrate the inner layer.. i wrapped more tape around it.  i put everything back to start it. at first only one cyclinder still.. but as i stood there watching it, the other cylinder just magically started working.. first a little white smoke, then it worked, and it sounded wonderful. and i set the idle, and rode it around town. later in the evening i started it again and it was back to one cylinder.
TOday i tried starting it, and only one cylinder works. only the front. i tried everything from yesterday, but no luck.
I've read all the posts about it and it sounds like its either a dirty carb still, the tci unit, the cdi unit, the breather tubes, or the mixture setting.
i think i want to try cleaning out the gas tank, replacing all of the fuel lines and breathers, getting a new fuel filter, cleaning the carbs again and dipping them this time.. and maybe that should do it. the bike has less than 6000 miles on it. there was a lot of gel in the float bowls the first time i cleaned them. i should also mention that there is some heavy backfiring going on.. both out of the exhaust of the cylinder that is not firing, and out of the intake! it blew a hole right through the cardboard air filter at the intake! i feared for my knee! one of the little cover screws fell out! i should mention too that fuel is just dripping out of the exhaust pipe that isnt firing. the lame cylinder plug is completely saturated when i check it. especially today since it would only idle with the choke on.. as opposed to yesterday, where i had both cylinders running, and it was idling so smoothly.. i actually was considering registering the bike asap.  but today, horrible.. yesterday was such a tease. anybody feel like talking about only one cylinder working on viragos anymore?? hah. thanks guys.