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..

A "skip" ( usually four stroking ) does not necessarily indicate an air leak.

If the engine is rich, it will do this. It may be that you have it too rich.

Check for a leak by:

Put a CLEAN piece of fuel tubing on the carb inlet nipple.

Open the throttle and turn the engine over until you can see the crankshaft opening, permitting you to see into the casing.

BLOW into the tubing. You should hear a HISS and feel pressure being released.

Put your finger over the carb opening to seal it.

Now turn the engine over as you blow through the tubing.

At some point you'll find that the pressure does not seem to go down at all. Hold the engine at this point, and keep blowing ( maintaining pressure ).

If you have a leak the pressure will go down after a few seconds. I doubt it though from your description.

replace the fuel line from the tanck to the needle and the needle to the carburettor. Also i would replace the pressure line and make sure the clunck isnt sticking. After that i would try to re set the engine