RE: Prop Help on MVVS 58cc
YOU ARE OVER-SPEEDING YOUR ENGINE!!!!
This engine reaches its peak HP number at only 6,700 RPM (or only 6,200, if it is the ProSport), so you are over 1,100 RPM over the top with this 'puny' prop. And the is a ground figure...
The engine should be propped to spin around 6,000 RPM on the ground, which means a 26x10 (Mejzlik), or a slightly smaller Menz, or Bolly.