bike cuts out and dies

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so ill be riding down the road and my 81 gs450t will just randomly stop running, simular to running out of gas, rpms will drop fast with a loud ass backfire, like a gunshot. at first i just thought it was a carb issue, so i took the apart cleaned the with boiling lemon juice, and replaced all the rubber and any work looking parts with parts from another carb i have for the bike. the bike still cuts out the same. my spark plugs have a very weak purple spark most of the tie, but rarely will have a thick white spark. the bike is running super rich with the air screw set to 2.5 turns out. i keep fiddling with the air screw, the bike still runs real rich, you can smell it in the exhaust. when y bike dies, i always take the plugs out ad check if i have spark. sometimes there is no spark in one cylinder when it cuts out. sometimes they still are sparking when i pull them out but weak sparks. i cant figure out if its the carbs that are too rich that are fouling the plugs or if its that i just have an electrical problem and all the gas isnt being burned every rotation and eventually just floods out. ive bought new plugs, and done lots of sanding and regapping. im thinking its electrical because my gear indication lights are going out one by one but some if the will randomly come back on. so the bulbs arent out. i thought i may have had a bad ground so i got a wire to connect the ground points of the rectifier and whatever that black box is next to it, to the battery negative. what are some ways to improve spark? should i try out a new plug? right now i have ngk b83s plugs. during a ride, once she gets warmed up, it dies out alot, once it died every half mile for a few hours, after it dies i check the spark, sand the contact a bit and let it sit for 5- 10 mins and it will start again. today i took the airscrews to 6.5 turns out and took out the air filter pad, and it made it the 15 minute ride home without dieing. i just dont know where the root of the problem is, is it the fuel richness causing the bad spark(fouling the plugs)? or is it an electrical issue causing a weak spark letting fuel build up in the cylinder flooding it out?