Ok. I have an OS 46fx that sounds like it has a small air leak. It runs good, but it will skip a little. You can hear it miss like its got air in it every once in a while. I checked all the screws. the only other place I can think it might be getting air is through the needle valve. I read some post about putting some fuel tubbing over it. Do you put it over the metal flap too or under it? Im pretty sure this is my problem, it is spitting some black oil out of the muffler like its getting to much air..