U need a datastream run w afactory tool to display values. The ignition parts are probly wearing out along w fuel system. Purchase a clymer or haynes rebuild guide this wk
The jets probly need ajust. Ucud hav dirty aircleanr causin them to clog. Also chec floatlevel setting. Buy a clymermanual for total repair&rebuild for that model
you can order one from any yamaha dealer or check e bay https://www.google.com/search?q=84+RZ350+service+manual&rlz=1C1OKWM_enUS816US816&sxsrf=ALeKk00U1zLmo85bQebLCpFSyV8qSc0pKg%3A1620136882094&ei=slORYI-hBZKk_QaB35mIDQ&oq=84+RZ350+service+manual&gs_lcp=Cgdnd3Mtd2l6EAM6BwgAEEcQsANQpWhYhWpg9W5oAXACeACAAUaIAcUBkgEBM5gBAKABAaoBB2d3cy13aXrIAQjAAQE&sclient=gws-wiz&ved=0ahUKEwiPwuCamLDwAhUSUt8KHYFvBtEQ4dUDCA8&uact=5