LOL, no language problem. I don't know why my profile says Samoa. I understand that running them lean can cause back fire, but on the extemely rich side they can "hydraulic" and cause the prop to spin also. This happened to me as I was continually richening to try to get a base line. I was mainly trying to find out if pumped engines respond to the "pinch" test differently than a non-pumped engine, since this is the first I have owned. Thanks for the input.