I tried using the search function but couldn't find any specific information—I've disassembled the carburetors on my 1972 CB350 and I'm ready for a deep cleaning. It looks like the late-style carbs have a large plastic passage plug located near the idle mixture screw (I've read on earlier models it wasn't plastic). My plan was to dip the entire body in cleaner to let it soak, however, I'm worried that would melt the plastic, no? If so, what is the safest way to clean the carburetor bodies without damaging the plastic passage plug? Thanks!