Hi, well I'm still working on my chopper, just finished welding it all together last night, my 1st question is my back tire size is 20", should I use a 24 tooth sprocket to get the speed need? 2nd question, I am replacing the stock carb with a cns-carb. should I dial it in right with the new pipes or should I stick with the stock pipes before I replace them? What should I do?