Re: Newbie needs some help!

Posted by sgtslag on Oct 03, 2011; 3:20am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/Newbie-needs-some-help-tp3386691p3388728.html

Don't know if this will help, or not, but your charging system is not working:  the bike is running off of the Battery, alone; the Battery is not being charged, so it is running down; when it gets too discharged to run the coils, and the other electrical items (lights, mostly), your bike dies -- no electrical energy left in the Battery to create a spark across the plugs, so no combustion will take place.  By the way, this is referred to as 'deep cycling' the battery:  it is not good for lead-acid batteries, and it will dramatically shorten its life.

That is the principle of what is happening with your bike.  Some finer points are as covered, already.  I would suggest checking the voltage across your Battery, when it is fully charged, and the bike is running:  it should be higher than 13 Volts [resting voltage (voltage after the vehicle has been off for 20+ minutes, and is fully charged) on a good, lead-acid battery, is 12.6 volts].  The Rectifier/Regulator can burn out/open, preventing any charge reaching the Battery.  They're nearly impossible to test, however, as the Regulator (maintains a relatively constant voltage to charge the Battery, but cannot make up for low/no voltage, only prevents it getting too high) is physically housed with the Rectifier [Alternator puts out AC, on the three yellow wires, Rectifier converts AC to DC, (+) red and (-) black wires, which then runs the bike's electrics, and charges the Battery].  Basically, the Rectifier/Regulator is a little 'black box' circuit, and there is no way to test the components within, from the external leads you have access to.  You will need to check the Rotor, the Alternator for AC output voltage (yellow wires), and then the Battery's terminals to see if the Rectifier/Regulator is charging the Battery.

Electrical circuits are actually fairly easy to troubleshoot:  divide the circuit in half, and test for a good signal, or voltage, at that point -- if present, the problem is in the latter half of the schematic, if the signal is missing, the problem is in the former half; divide whichever half of the circuit has the problem, in half again, check for the appropriate signal/voltage -- if present, the problem is in the remaining latter half, if missing, the problem is in the former, remaining half of the schematic.  Keep dividing the circuit in half, until you find the failed component.

To apply this to your bike, you could check for AC voltage on the yellow wires:  no voltage indicates the Alternator/Rotor is not working; if AC is present, then the problem is somewhere between your Battery's posts, and the Alternator's yellow wires.  At this point, the AC goes directly to the Rectifier/Regulator.  If AC is present at the (yellow) input wires, then the Rectifier/Regulator should have a DC voltage on its output wires:  if DC voltage is present, then the Rectifier/Regulator is working, but somewhere between it, and the Battery, is a problem.  That is a large area, as every electrical component is, at least indirectly, connected to the Battery, possibly through the fuse block, switches, and maybe in series with other devices -- divide the schematic in half, and measure...

Take some time to peruse the schematics, and pay attention to the color codes used for the various wires.  I use different colors of highlighter pens to mark them on photocopies of the diagrams (that way I can mess up the copies, while keeping the originals pristine).  You will need to know the wires' color codes to locate, and trace them, on the bike.

If you do not have a Digital Volt Meter (DVM), get one.  They are available from nearly every DIY box store:  Menards, Home Depot, Lowe's, Harbor Freight, etc.  They can be had, on sale, for around $5.  You need something that will measure AC/DC voltage (20 volt range is ideal for vehicles, but you can use it around the house for testing outlets, at 110/220 VAC), resistance, and a continuity test is good, too (aka, diode tester -- beeps when there is a short between the leads, indicating continuity).

Hopefully this background information will help with this problem, and potential future electrical issues.  Cheers!