Once its warm (very quick with no coolant in) you wont need the choke, let the choke off and it will help it rev a little, also you can adjust the throttle stop to set the idle
But with airleaks, lean jetting, static timing and no exhaust its never gonna sound good is it!
The gearbox spinning is fine and it sounds like its firing on all cylinders to me, my old cvh engine sounded very similar with no exhaust on first start