I need to remove the carburetor assembly for cleaning. I removed the choke cable per Clymer manual instructions and loosened the throttle pull/push cables. I also loosened all four clamp screws to the point of the clamps freewheeling. When I try to lift up the assembly it won't budge. The whole bike moves back instead. What's going on here? Any tricks before I just put the whole thing back together and tow it to a mechanic?