Try cleaning up the inside lip of the silencer and also the whole outside of the header pipe with some emery paper, there may be a few small burrs on both.
Thanks! It looked as if there was a metal piece welded but the once I removed the gasket and cleaned it up it fit fine.Try cleaning up the inside lip of the silencer and also the whole outside of the header pipe with some emery paper, there may be a few small burrs on both.