I have my Ryobi running great now and working on a second one, I love it .
It is so reliable and now smooth running as well.
I think the motor was detonating on the coleman fuel as the compression has improved with time.
I am now using 95 octane petrol and a 20 x 10 master prop with plenty of weight in it to smooth the pulses out.
At peak rpm the vibration is minimal and with a electronic ignition it starts second flick once primed.
Opening up the thrttle from about half produces no further increase in power though so I think it it over proped but I don't need the power .
Thanks for the replys and help.
I have a 2 long shafts and 1 short but they all have the good reed valve!