Wobble is not acceptable on any engine...The taper on the Ryobi crank is very close to the front bearing, and any runout at all there is highly unlikely...The best way to make it square is to put some Loctite on the taper and tighten the flywheel as tight as possible..Let it set up for a few hours and take the hub off..Bolt the engine on a mill table so you can slowly rotate the flywheel and mill the top surface perfectly flat and 90 degrees to the crank..If the hub is drilled and tapped correctly it will not wobble when put back on...Without a mill there is no way to make it perfect, as you can't be sure the top surface of the flywheel is 90 degrees to the crank...
Unless the flywheel is held in the lathe ON THE TAPER it's not possible to get the top surface perfect....
U S 41s had this problem a few years ago...The fix was to put the flywheel on a tapered shaft in the lathe and machine both front and rear surfaces, and make a new hub.....
THIS IS NOT TO SAY THE PARTS YOU RECEIVED ARE NOT PERFECT, don't anybody get all hyper [:@] and start flaming