My bike has been running rich since I bought it a year ago (with 5,914 miles on it). And the idle mix screws were only one turn out from bottom. I recently switched the gas valve to reserve and rode it to Skid's meet at Hamburger Joe's. It missed a little on the way back. So, I put a half bottle of Gumout for high mileage engines in a tank of fuel and rode it about 25 miles. It started running really ragged and the fuel filter had black gas in it when I checked it. After sitting overnight, I rode it about 20 miles the next day and it ran better. The next day I ran the tank out and it ran fine the whole time. Then it sat for a week while we went on a cruise and ran ragged again when I rode it after returning. The fuel filter now has clean appearing gasoline in it. I just received a new filter to change it out with. So, yesterday I replaced the spark plugs that were really black with soot. They were NGK DPR7EA 9 plugs and may have been the original plugs. The new plugs are NGK DPR8EA 9. Now it runs great again. I think it is still running rich and I turned the mix screws to 1/2 turn off the bottom. It starts instantly and runs great with just a tiny bit of occasional hesitation when I roll on the throttle from 3K rpm or below. So now the plan it to check the fuel level in the carbs and I think someone mentioned that the fuel enricheners could cause a rich condition.
Any other ideas for what to check/adjust without taking the carbs off?
Thanks!