I guess my point is this: Without using a tach to develop an experience-based calibration for what is "about right," how is a beginner supposed to know what they're doing? I rather doubt that many of us have an instinctual understanding of it all. For two-strokes, such the OP asked about, a tach isn't needed by most people. That flips when it comes to four-strokes, with most people needing one to safely and accurately tune their engine.