Sounds like it loaded up on fuel. Did you pull the plug and use the electric starter to turn it over before hooking up the fuel line to it? Some engines will start with out doing this, but others really need to get the oil removed from the cylinder before firing it up. My OS .46 needs the plug pulled and the after run blown out before it will run good. My Supertiger GS-40 will fire up with out pulling the plug, but needs about 20 seconds to get the oil out of its system and start to run good.

Hogflyer