The Sirio .27 generally runs much stronger than what you've described. I would get the engine started, warm it up a bit, then let idle for a about 10 seconds. Then, pinch the fuel line (it doesn't matter where). If the engine continues running for longer than 6-7 seconds, then the bottom end is too rich. If the engine stalls more quickly, then it's probably too lean. Try it out and let me know what happens. The high-speed needle may need some adjustment as well, but getting the low-speed needle in the right range will help.