I looked up carb stix................this was also a mystery to me! I have an air flow tool that I use on the VW, but it would be difficult to use here. Found several people on the Aprilia forum saying that syncing is not necessary with the single cylinders?? There were comments on making sure the carbs are jetted correctly and opening at the same time, but nothing for synching. If this is correct, that would be great for me I did a bench test with a strobe light and was able to get both carbs opening at the same time (they were really close already). Also, after inspecting my carbs I found that the vacuum ports are not in the same place on each carb (like they were on several of the videos that I watched about synching) and the port to the throat of the carb is slightly different on each? One of the vacuum lines is connected to the fuel cock where the fuel comes to the carbs. The two ports on the other carb are plugged? Would this make it not possible to sync? Mikuni BST 33's on a 2000 Aprilia Pegaso. Any thoughts?