I just soak the whole engine, generally, I remove the head and back cover, maybe even the front if it has it. I would probably go ahead and take the rest of the engine apaart, however I can never get the piston off. But yeah, if your just trying to get the outside, if you've got a little nerve, you could even take some lava abrasive soap and a tooth brush and go at it. I do that on the crap on the mufflers.