Motorcycle Repair: non-starting sportster, screaming eagle pipes, air fuel mixture

Question
QUESTION:   A neighbor asked me to get her 1991 883 Sportster running after it sat in storage for several years. I drained and replaced the gas from the tank and carb and the bike started. It idled OK but backfired and stumbled in the midrange and was basically unrideable. The plugs were fairly new and clean. Eventually, it wouldn't start at all, so I assumed the carb was clogged up from sitting so long. I disassembled and chem-dipped the carb. I didn't see any obvious blockages and there was very little varnish in there. I just put it all back together and it still won't start, backfiring a good bit while cranking. It has screaming eagle pipes and air cleaner, but has the factory pilot and main in it. Not sure about the needle, but I assume it's stock since the mixture plug was intact. I drilled the plug and backed the screw out 1/4 turn while I had it apart. I'm not sure how to set the static timing, but I can't see why anything but bad gas could have happened in storage. Any pointers?

ANSWER: I would suspect that you have a carb problem. Its really hard on a carb to sit for a long time, vent holes get clogged with varnish and dirt. I would remove the carb again and clean it. Remove the intermediate and main jet at well at the air/fuel mixture screw. If it wont idle then there is a blockage in the air/fuel mixture screw. If it wont rev up, then there is a blockage in the intermediate jet.
Good luck and happy riding
Mike

---------- FOLLOW-UP ----------

QUESTION:   Followed your advice and pulled the carb again, specifically removing the mixture screw and cleaning within, something I neglected to do last time. I'm 99.9% sure there are no carb blockages now. I noticed while cranking that only the rear cylinder was afterfiring (flash from the pipe). I pulled the plugs and the rear was more wet than the front. I checked the gap and checked for spark by holding the plug against ground. I was unable to get a spark from the rear wire, although I would think it must be firing occasionally to get the afterfiring. I'm in the process of testing the coil, but I need to get a .33 MFD capacitor for the jumper test spelled out in my manual.

Answer
Do this test. Swap plug wires on the coil. Now turn the bike over and see if you get a spark on the same side of the coil. If you are getting a spark opposite of what you got before then you have a bad plug wire. If it is still the same you probably have a bad coil. When replacing the coil I always replade the plug wires
Good luck and happy riding
Mike