I currently own a 1981 Yamaha XJ 550 Seca. It is in good condition and sat for many years with gas in tank and carbs. After thouroughly cleaning and flushing the entire fuel system/carbs, it starts up nicely but has a number of problems. The bike does not idle no matter where the idle adjustment is and it will not rev down fast enough after revving the motor. When you rev it up or drive it, the motor will not rev down and you have to either kill the motor or force it slower by putting it in gear and braking/clutching combo. Any ideas as to what could be wrong would be appreciated. The bike has been tuned as well.