Today I picked up an 1982 cx500. I do not know much about this engine. The engine idles good but anything above 3000 rpm's it knocks and shakes like crazy. I have the engine out of it now and the heads, clutch, and back and front covers off of it. I have not found anything wrong yet. Could it be an rod or crank bearing or am i just missing something. I would like to get your guys input before I go any further. Any and all help would be appreciated. Thank.