Please bear with me, gents. As some of you may know, I had a surging problem on my R100R that seemed eliminated with a carb rebuild. However, a rebuild meant setting up the carbs and tuning the bike, and I think I found more wisdom on the net than I can manage. :huh The often quoted sources are: http://bmwmotorcycletech.info/synchcarbs.htm http://wisconsin.airheads.org/content/view/33/51/ I found this one particularly simple and appealing, however it requires a good "ear" which is not what I have: http://rossmz.blogspot.com/2008/12/tuning-40mm-bing-cv-carburetors-for-bmw.html Being a recent airhead owner, I certainly do not have the experience to know what is the right setting or sound to expect from the boxer. I have a few questions on which I hope your collective wisdom can shed some light: (1) Do the mixture screws have a huge effect on the idling or are the idle screws sole masters of the idling of the bike? I managed to get a balanced idle using only the idle screws. (2) Leading from that, do I have to tamper with the mixture screws stock settings (3/4 turns out) if the carbs can be balanced with a TwinMax? Any benefits to doing so? Or should I monitor the plugs before attacking the mixture screws? (3) Backfiring is that an evil thing? Is it an indication of too lean? Do I adjust the mixture out to rectify that? I do apologise if my questions are basic and the answers seemed obvious, but I think it is important to get the basic rights and my trawl through the internet unfortunately turned up more information than what is useful to me. Finally, I drew some inspiration and comfort from Duane at http://w6rec.com/duane/bmw/tuning.htm when he said: A good BMW twin tuner with a lot of experience will almost never find a perfectly tuned engine. Each of my mechanics went through a "crazy period" when they were learning to tune carbs. While riding their own bikes, every few minutes they would reach down and do a slight tweak on a carb. Eventually, they learned to accept that it would never be perfect. The very best that you will ever achieve is a workable compromise. Be happy.