Ralph, I agree that these low CR weedies and chainsaw engines dont really react much to ignition timing. The point of advancing the spark timing is to maximize peak combustion pressure - and therefore power - by starting the combustion cycle early. With low CR, the engine just can't generate any more peak pressure beyond a certain point, no matter how early you spark.

Power timing is only really worthwhile if you raise the CR and then switch to a little higher octane.