Hello all, I'm new to riding and working on bikes. When I got my license, I didn't want to go with the normal ninja 250s and such so I decided to import a CBR250RR from Japan with only 3994 km's. I live in the US so obviously parts are not available here so every time I need something, I have to spend an extra $30 on shipping from Australia or Japan and wait a few weeks for each part. When the bike arrived, it was not running, the choke cable was broken, the body was from a '94, and the brake pistons were seized. So far I cleaned the carbs and put in new float bowl gaskets, changed the oil, replaced the coolant, replaced the choke cable, fixed the brakes, replaced the fuel petcock valve, and cleaned and sealed the fuel tank. After putting everything back together and about fifty failed startup attempts, the bike started up. It was running rough and at idle it kept going from 500 RPM to 4,000 RPM. Also, the muffler was cold to the touch so I'm assuming it wasn't running on all cylinders (I'm no pro so I can't tell by sound). Unfortunately I couldn't test it for a ride because the tires are dry rotted and it was pouring rain. The next day, I tried starting it but it wouldn't start and kept backfiring. I decided to check the spark plugs and they were black and brown and smelled like fuel (The second and third pictures attached). I cleaned them and put them back for now but I'm not sure what to do. I figured I need to adjust the pilot screw to fix the AFR but I'm not sure what else to do. Thanks!