my friend, if your only getting 42 mph you have a problem.. Might be your running way to Rich with that 115 main jet,, or something... i have a Super 8 2t with only a 88 main jet, racing exhaust , and variator/Sliders, modded air box.. and i get 47MPH gps verified. 45-46 all day . My close friend (also member here) has a super 8 2t with the sh**tiest naraku 70cc kit on it, with just a 92 main jet and STOCK EXHAUST modded and welded and get 49mph . he weighs about 230. On mine when i drop down from 88 to 86 it leans it out to where its alittle faster, but to lean. BUT i also tried a 90 in their and it dropped down to 43-44 mph. To big of main jet means sloppy wet combustion , to much gas,,, not enough clean burn.