on all the bikes and 4-wheelers my family owns we usually go down 2 main jet sizes and then 2 or 3 for the pilot jet but it really needs to be tweaked with and played with at the altitude you are jetting for. so we just tune our machines for where we live at and then its pretty safe to ride all the places we go. we live at about 5,000 and so thats what we jet for and it runs much better at 8,000 with 5,000 jetting than it would 8,000 with sea level rich break in jetting which is what most stock jetting is if you know what i'm talking about. you could also try tunning for the altitude by using a chart or guessing but with my experience in that it usually ends up still needing to be worked on. but one pilot jet size usually covers about 2-3,000 feet or so to answer your question but you really can never tell it's all different depending on what brand your carb is and what brand jets your using there are a lot of factors involved in the equation.