Motorcycle Repair: Overcharging

Question
Hi Wayne, I have a 1980 Honda xl80s that I am restoring for a friend of mine, I am getting all the lights working and found that the alt was fried so I got an oem one from eBay brand new now it will fry all the new bulbs and turn relay I cannot keep putting bulbs and relays in to find the problem I also replaced the silicon rectifier still fried the turn relay I have not hooked up the new headlight or taillight in fear of burning them out as well do these have voltage regulators to keep them at 6 volts? I am very stumped other that that the bike runs great. Any ideas or solutions would be very helpful at this point.       

Thanks for any help Andy

Answer

Hi Andy,

Many older Hondas used what is called a "balanced charging system".
This was okay when new but as time goes on can cause some
difficulties.

The system used all the components of the charging and lighting
circuits to make sure the voltage was "balanced"

In other words all the lights must be connected and working and
the battery must be good and installed too.
If any part of the system is missing or has a poor connection
then the voltage output will be excessive.

When all is connected the voltage was usually satisfactory
so as not to burn out bulbs so quickly.

As I mentioned if any part becomes detached or a taillight
bulb burns out then the headlight will likely
get too much voltage.

The better solution is likely to find a universal 6 volt AC regulator and
connect it to ground and to the yellow stator wire that
feeds power to the dimmer switch.

More expensive is the small one wire regulator
used on 6 volt Yamahas in the seventies.
These are sometimes found on ebay or such.

http://www.ebay.com/itm/1979-Yamaha-XT500-DT125-DT400-TY350-Regulator-/190921012

If you connect one these regulators to your dimmer switch lighting wire
and ground the frame really good it should shunt the excess
voltage to ground and protect your headlight.

If you connect all your bulbs and battery the voltage might be okay
but you have to check it with a multimeter and make sure
nothing will vibrate loose.

There may be other simple regulators made for scooters or moped
that will work as long as they are 6 volt.

If you try to reduce power with 12 volt bulbs or such
you may find the ignition lacking enough voltage
to run properly and the lights will be dim.

Let me know if you need more info

Wayne S
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