I bought a 1980 XL500S brand new. After a few years the turn signals began blinking slower and slower until they would not blink at all. It turns out that the 6 volt alternator that charges the battery is notoriously weak and with a little corrosion the battery electrical system became totally unreliable. There are separate alternator circuits to run the headlight and ignition so those are working just fine.
At one point I gave up driving on the streets and just used it off-road with my kids.
Recently I decided to try and re-licence the 500 and use it mostly for short trips on streets and back roads. I went through the entire electrical system and cleaned and waterproofed all connectors. However, the turn signals would still not blink even with a new thermal flasher and a fully charged battery.
I did not want to go through the of trouble converting to 12 volt so I did a bit of research and purchased the following from Superbrightleds.com .
Item || Part No || Description || Qty || Price Each
Flasher || FL2-RED || LED Bulb Electronic Flasher: 2 Pin Red American Flasher || 1 || $12.95
Turn Indicator Diode || MDK-1 || Metric Bike Diode Kit || 1 || $2.29
Tail Light || 1157-R19-6V || 19-LED 1157 Bulb: Red 15 Degree Dual Intensity 6VDC || 1 || $7.95
Turn Light || 1156-A19-6V || 19-LED 1156 Bulb: Amber 100 Degree 6VDC || 4 || $7.95
Speedometer Lights || BA9SF-W-6V || BA9s LED Bulb: Cool White 180 Degree 6VAC/DC || 3 || $1.98
Neutral Indicator || BA9SF-G-6V || BA9s LED Bulb: Green 180 Degree 6VAC/DC || 1 || $1.98
Turn Indicator || BA9SF-A-6V || BA9s LED Bulb: Amber 180 Degree 6VAC/DC || 1 || $0.98
High Beam Indicator || BA9SF-B-6V || BA9s LED Bulb: Blue 180 Degree 6VAC/DC || 1 || $1.98
Even though the Flasher is listed as 12 volt there was a review that said it worked on a 6 volt system. I installed all of these items and they worked perfectly. The turn signals flash brightly and regularly and the tail light goes brighter when the brakes are applied. The led lights should draw a lot less power so hopefully the alternator will be able keep the battery charged.
The TURN INDICATOR DIODE should have been necessary to prevent back-feed to the non-selected turn bulbs. However the LED TURN INDICATOR bulb has such a high resistance that the non-selected bulbs flash very very dimly. I am not going to install the diode and see how it looks at night.