Hi carlosponti,
I looked it up at outdoor distributors and it is a standard Homey engine. Either 25cc or 30cc. The size of the engine is molded into the cylinder flange to the right of the carb mount. You can also check the exhust port, after removing the muffler. If it has a bridge in the middle of the port, it is a 25cc, if not it is a 30cc. The best size carb is 11mm. Also don't forget to tap and plug the hole above the exhust port with a 10-32 0r 10-24 screw. This will boost compression and power. There is a ton of tips on conversion and hopup of these engines at RCU and elsewhere on the web.

Regards, Dave