I'm pretty bad about keeping my cars clean, but I do occasionally give them a partial cleaning. I will spray my engine while still mounted on the car with brake parts or carbuerator (did I spell thatright?)cleaner, then use a toothbrush to loosen everything up, then spray again to rinse. Works great for me.

Given that you just bought this thing, it is probably a good idea to completely remove the engine and do at least apartial tear-down.By that I mean remove carbuerator, pullstart/backplate and then spray out with cleaner. Lubricate it and put it back together.