My bike has a digital voltmeter installed on the dash, no variations, always around 14.2V
see
http://web.ncf.ca/ag136/volthermometer.htmI also thought reverse spikes may have caused problems, so I stuffed in a reverse-biased diode across the LED power line. No change, they all died anyway.
see
http://web.ncf.ca/ag136/dashLEDs.htmlAnyway, the LEDs and the epoxy are pretty cheap. If they were easier to replace, I wouldn't care as much, but to change a dash LED, you have to undo both the fairing side pockets, remove the windshield, remove the dash bezel, remove the instruments including the damn speedo drive, then the bracket and you're there. Assembly is the reverse order of disassembly (CB160 Service Manual jargon).