Re: how to do this?
Hot Pant's, opps sorry joking with yah UnskilledMachinist.
I agree with BikeguyJoe, on top of Carburetor there should be and adjustment screw just as there should be one at the handlebar where the throttle cable feeds into your twist throttle hand grip, is this making sense to you, I like to adjust mine from the carburetor first leaving bout 5-6 threads into the twist on cap on top of carb, then I work on adjusting the cable from the hand twist throttle until the engine will idle.
Try re-adjusting the clutch cable leave as much room for adjust at handlebar adjustment screw then, have someone if you don't have needle nose vise grips to hold your clutch cable and mark it with black magic marker on the cable where it just release's or dis-engages from motor to allow rear wheel to spin freely, then just keep playing with it till you've got it where you like it.
Remember if this is your first engine/build, your next one will hopefully be less frustrating once you've gotten thru the learning curve you'll be able to look back and laugh.
Peace & Good Luck Crazy Horse.