Toward end if SOHC4 production years, the regulatory agencies tired of brow beating the auto manufacturers into ever more silly mandates. (Because they could, primarily) So, to expand their purview, they turned their attention to motorcycle vehicles. Beyond the smog mantra, their were already pretty stringent rules about noise emissions for autos, it was an easy rule to make regarding motor cycles. Honda complied and made the 77 78 exhaust systems quieter. Using more baffling and thicker steel also made the exhaust heavier, as well making them quieter. This was certainly true for the 550 models. Government agencies had quite a different take on"performance" than actual performance enthusiasts. And it wasn't long thereafter that the nation speed limit was set for 55 mph, in order to reduce the loss of the taxpayer population. But, I digress.
