you sohuldnt run your engine rich to get it to run, sounds like you dont know how to tune, if the top of the head is black i beleive thats from running too rich (or lean, i forget) if its hard to pull then that means its probably flooded (rich) and yes the sleeve is tighter at the top, this is called pinch, without it you would have no compression, also please read your post first, some of it is hard to read