You have 2 methods, but don't cut wires. Drop tank and desolder wires from old speaker. This can work unless you have other wires preventing easy access, like battery and volume pot (if they are on fuel tank.
Otherwise, clip the wire strap in the bundle and unplug the yellow and white wire plug that goes to the speaker. Remove speaker and do work on bench, reinstall and replug in speaker.
Make sure you do not pinch any wires. Speaker wires that touch chassis ground at the speaker, or frame will short the audio amp. G