Main Motorcycle: '01 Triumph Bonneville
Join Date: Sep 2012
Yes I did solve the spitback by merely turning the mixture screws out 3 turns on 40-size and 2.5 turns on 42-size. The adjustment of the mixture screws will be specific to your bike, but they really make the most difference when it comes to idle and just-of-idle performance.
I do get spitbacks (or coughs) sometimes, still, and it's usually when the engine is cold. Thus, I believe the problem is caused by an overabundance of air and too little fuel when the butterfly valve is closed to just immediately cracked open.