No, no re-jetting needed for me. I had to tinker with the carb for about half a day of riding to get it "just right" but heres what I did: set the clip on the needle to 2nd from top, rode it for 10 minutes to warm it up, adjusted the air screw and then the idle screw, rode it again to see how she felt, messed with the idle screw again, rode again, etc. I finally ended up with it idling (not perfectly, but really good for now) where the rear tire will spin, but only very slowly. It will idle good without choke, and a tiny rough with choke, but it accelerates a lot better and has a slightly higher top speed. I'm going to the 60cc with a bigger carb this winter, so I'm happy for now.