Re: what are the long term effects of an air leak?
Before breaking down the engine, I would check to make sure that you aren't just running too lean. At one point I was running my engine with too small of a jet and it would bog down/ get too hot. A light brown color plug indicates a lean condition. All of these engines make rattling noises. Mine rattles a TON when revved but this is in fact coming from the clutch.
If you order all of these parts and end up not needing a rebuild, then it will be a waste. I would make sure to correct your fuel to air mixture first before breaking down the engine.