Small Engines (Lawn Mowers, etc.): Ryobi String Trimmer, gas tank, gas oil

Question
After use, this thing leaks gas/oil mix.  I have tried storing it "engine up", "engine down" and horizontal - still leaks.  Any ideas?

Answer
 Hello Ray:

 Check the Gas Tank Cap. If the Cap isn't Venting Properly you will have this Problem. Hope this helps. I am here if you Require more Assistance. Let me know what Happens, Please. Thanks. Be Safe.

 Good Luck

 Respectfully

 John