Start with the carb off, look into it as you turn the throttle. If the barrel doesn't move up and down, you have something wrong. If that's the case, check the cable in the throttle to be sure it's seated correctly (and make sure the barrel is the right way up), and check the cable at the throttle grip. On my first build the cable's stop pulled out of the plastic in the end of the throttle grip and tore up the channel for it and I had to replace the handle.