I bought a rossi 60 from someone here. I can't find the original post anymore. The engine was missing the 2 bolts that hold on the header, or muffler. I can't find anything to fit it. I called a rossi dealer, and he said there were 3 different sizes, but 4mm should be right. I bought a 4mm, and it doesn't want to thread. I don't want to force it. My tap and die set lists a 4x7 and a 4x7.5 thread pitch. The engine looks old, and has side exhaust. If anyone know the correct size of the bolt needed, or where I can buy one please email me or post here.