I have an 82 Honda 450 Nighthawk motorcycle that I'm rebuilding and I need to tune/balance the carbs. I have them bench-balanced and reset the idle screw on both. Now it runs a lot better, but every 10-15 seconds the idle raises and it starts sputtering out the carbs.
I assume this is just a lean mix, but could it also be vacuum or something? I don't want to tune the carbs just to realize that I need to fix something else and tune them all over again.