Motorcycle Repair: idel too low/ backfire, fuel mix, throttle cable

Question
QUESTION:  My question to you is which screw on the carb sets the idol and which way do I turn it to increase the idol? I know I need a new battery. Would that be another cause for the backfire when I come off the gas at speed or is it my air fuel mix to lean?

ANSWER: What year and model?
Mike

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

QUESTION: 92, UltraClassic

Answer
If you have a bad battery, it will cause the backfiring problem. Not enough juice to make a hot spark. Change the battery and if its still doing the same thing, then let me know.
Look at the top of the carb and you will see the throttle cable. Close to it is the idle screw. Start the bike and let it warm up, then adjust the screw so you get the idle at around 900 RPM
Good luck and happy riding
Mike