Motorcycle Repair: Spark Plugs - Engine Miss, correct heat, gas additive

Question
We recently bought a used Suzuki GS650L which had sat for several years. Redid the carbs, new spark plugs, changed the oil, replaced tires, brake shoes, rotors, cleaned gas tank, no rust, flushed tank, added good gas and some gas additive that was recommended. We have a friend who works on bikes a lot and he has been our guide. We had a small miss in the motor, he said to keep changing the plug on that bank, that since it had sat for awhile b4 we got it it was dirty and needed to be rode for awhile. Once you change the plug it runs fine until next time. He tested it with switching out the plug wires the alternate bank. How do you feel about this? And do you have any different suggestions? Also wife is a new rider (hadn't rode in 20 years)so she uses the bike around the neighborhood learning to ride again. Does the slow riding hurt the bike with this problem, it's air cooled and shaft driven. Any suggestions needed to make sure it doesn't over heat, etc. Thank you for your time and advice.

Answer
Carl, there are a few things we can do. but first, for some reason the one cyclinder is getting to much fuel either the mixture is set too rich or there is a carb problem. secondly im assuming the one plug just fouls and yes putting a new one in is a way to go but not the right way. Your wife riding slow around the neighborhood is not the greatest on plugs either, sometimes they dont get to the correct heat range to clean themselves so as long as she is slow riding no highway stuff put a hotter plug in it so it will clean itself and not foul. im betting on the one cyclinder in question has a carb issue and with this fixed and a hotter plug she would be just fine.

Eric