don't worry about the carb being a zama! most of the stihl products use these as do many others. all my little echo weedies have them too. the pump diaphragm and check valves are made of a better material than the walbro and don't dry and curl up after a long period of no use. be happy

also the numbers don't mean much as ryobi has made millions of these engines over the years. i doubt anyone out there knows what they all mean. your numbers are probably for an "export" product. the important things are number of rings and weather or not it has decompression slits in the cylinder.

oil: disregard what the fuel cap says, they're just trying to cover all bases as this thing is meant to be used by the average dumass that hasn't got a clue. if you have an echo dealer they'll have a nice 50:1 oil. otherwise mix per the oil manufacturers recommendations.

and have fun,

dave