HRS §291-22
No loud exhaust or muffler changes on motor scooters
This law makes it illegal to drive a motor scooter on public roads if its exhaust pipe or muffler has been changed from the factory design to make the engine louder. It applies only to motor scooters as defined elsewhere in state law.
everyone
The statute, as written — Regulation of exhaust pipe and muffler
It shall be unlawful for any person to drive upon the public highways any motor scooter, as defined in section 286-2, the exhaust pipe or muffler of which has been so changed from the factory design as to increase the volume or audibility of the explosions within the motor thereof.
Sections this one refers to
§286-2 Definitions for Hawaii's vehicle and traffic laws
LawTrove is not legal advice. The summary above is a computer-generated restatement — the authoritative text is the official version linked above.