both of mine have always ran as you have described, to be sure you dont have an air leak and are running too lean just take out your spark plug and see if it is a nice medium brown color, if it is then you are probably ok, but if it is very light brown like more of a gray color or even kinda white, DO NOT RUN your engine again until all the areas prone to loose their seal are fixed or you will cook your engine and be looking at a rebuild or a new one.