Aero nut,
Tests on the 23cc Shindawa indicated that higher octane fuel helps. However before I could finish, it developed a carb problem and my wife insisted that I help get things ready for the Holidays. Waiting on a gasket set and finishing the HD list.

Besides the Stihl 35cc I am going to try an Echo 38cc and a Zenoah 40cc that came out of a backpack blower. I don't have anything in the 40 + range but a 75cc poulan and 81cc Homelite.

Will