The ryobi has a seal out front with a bearing behind it ( unless I have identified my engine wrong ) if it had a front sealed bearing you could bulid the prop hub to set against the inner race.  I'm going to pull the engine back apart and clean everything then put it back with a little loctite on the inner race and reassemble it. If that does not fix it I will cut a groove for a circlip and solve the problem.
The engine runs to well when it don't have a problem to junk it out.
I was able to get 8000rpm with a 18x8 MAS which I think is reasonable.  It should pull my 14lb SPAD around better than the wore out  weedeater engine I have on it now, it has little compression left but runs.
Thanks for the help any comments,ideas or observation are greatly appreciated

Rex