I just tried to break in my NIB K&B .28 using Sig 5%nitro with 20% all castor and a 9X4 prop with the factory plug. I used the standard procedures , not too rich not too lean, let it run a few then let it cool, start over. When I got the engine it was particularly stiff at the pinch point so before I did anything I lubed the top end and bottom end and worked it over to get things real slippery. I just did a tear down inspection and I see the piston is deeply scored!! [X(] There is no problem with the cylinder that I can see which surprises me since the chrome plating on the piston should tear up the softer aluminum bore. It is almost as if the piston never got plated or something. Has anyone else had this problem?