Charging system failure

[motormike]

New battery lasted several hours but eventually would not crank the bike. After recharging battery on the bench, finding only 12 volts at battery terminals with bike running, revving, no change First notion is bad stator Secondly....what else could it be?....AND before I go after the stator, are there any more test procedures that might save needless disassembly?

[mousewheels]

A good battery getting discharged while the ign switch is 'off' or 'lock' position is a symptom of a bad regulator. Good side of reading your problem, is there's no melted wires mentioned, and the battery takes hours to go flat. Stator could be just fine

There are some resistance checks in the service manual.

Also, how's your headlight output? The coil used for charging output is 'tapped' at less than the full turns to give a lower voltage for headlight drive. If the headlight lights up well at riding speeds, its another sign of hope for the stator.
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[motormike]

Right....No signs or smells of burnt wiring....No voltage loss with key off.....Headlight was normally bright with no sign of being affected by the decreasing voltage while at the same time it was evident that the turn signals, stop-tail light, and horn were being adversely affected.......Have located rectifier/regulator and next step is swap known-to-be-good unit from spare bike, see what she reads then on the meter Thanx mousewheels for making me think a little....your input was a help.....result to follow

[Singo69]

see what the stator puts out on the charge lead on the battery, if its less then 12v, its bad/even if it is not consistent

[Bear45-70]

see what the stator puts out on the charge lead on the battery, if its less then 12v, its bad/even if it is not consistent

That makes no sense what so ever and helps not at all. First off the stator isn't the only component in the charging system and the stator is NOT directly connected to the battery. The AC from the stator is rectified in the regulator/rectifier (or rectifier/regulator if you prefer) then sent to the battery as DC, which the regulator controls the voltage level of.

The head light is driven by AC from it's own coil in the stator and has nothing to do with the DC charging system.

[eliteguy50]

Brake light, turn signals, and horn are weak at an idle on a bike with a good electrical system but dead or missing battery. That is a load issue where the battery acts as a capacitor.

[Bear45-70]

Brake light, turn signals, and horn are weak at an idle on a bike with a good electrical system but dead or missing battery. That is a load issue where the battery acts as a capacitor.

His battery going dead in a couple of hours and only showing battery voltage at the battery when the engine is running and revved up say, NOT the battery but the charging system isn't charging. Whether it is the regulator/rectifier or the stator will only be known by proper troubleshooting (the right way) or just swapping parts (the expensive way).

[Singo69]

I hate to say it, but bear is right. if you want it fixed quick, you gotta have those parts in hand $$$$
or bench test the stator (the right way).

or you might have a bad ground somewhere that is draining your battery!

[motormike]

As stated previously, have a spare '85 Gyro in good charging condition. No parts cost involved with a swap. However, meter shows no increase when in-line on good bike, just stays constant 12 volts. At the regulator there are 4 wires, red-white-yellow-green. With bike running, meter on AC voltage, I'm finding 12 volts AC across red/green, finding approximately 1 1/2 volts AC across red/yellow, none across red/white. Have not yet found service manual (free) online.No reference tonight. Good news is that I've found an '86 Gyro for sale with Honda service manual included. WILL BE BUYING ANOTHER GYRO tomorrow.

[mousewheels]

Hi,
Thank the site owner and contributor's for this, there are Gyro service manuals online here at Hondaspree.net.

Link: Service Manuals

Good luck on your next Honda Gyro - having more than 1 is usually a good thing

[Singo69]

check if battery will take a load.

[mousewheels]

As stated previously, have a spare '85 Gyro in good charging condition. No parts cost involved with a swap. However, meter shows no increase when in-line on good bike, just stays constant 12 volts. At the regulator there are 4 wires, red-white-yellow-green. With bike running, meter on AC voltage, I'm finding 12 volts AC across red/green, finding approximately 1 1/2 volts AC across red/yellow

12v Red/Green is low. Measuring AC across red/yellow is mixing AC with DC. We cannot tell if the 12v Red/Green is a regulator problem, or if the AC input is low.

One idea is to disconnect the regulator then measure AC from White to ground, AC Yellow to ground to ground to verify stator functionality. Now connect the regulator, and re-measure the white to ground and yellow to ground. Sometimes the regulator fails in a manner to drag down the AC stator outputs. The independent test may help isolate the problem.


-- Diagram from the Gyro Manual --
Here's a diagram from the Gyro manual. You will want to rev the engine up to the mid rpm range to duplicate the readings. At idle, the output is on the low side for the headlight and charge side. Result is a dim headlight, and little or no battery charge. Once the rpm's build, the headlight gets to full brightness, and the charge circuit comes into play. Voltages noted are at approx 5k rpm. Detail is presented later in the oscilloscope section.

Gyro_Charging_System.jpg (137.87 KiB) Viewed 8418 times

-- Stator coils --
A photo of the stator confirms the charge/lighting coil is a single coil. A short in this coil dumps energy which would otherwise go to the charge and headlight circuits. If shorted, I have found the charge and headlight circuit outputs to be compromised. If stator output is in question, ac voltage measurements of both coils is a good idea.

For me when troubleshooting a weak or dead headlight *and* bad charge output says 'check the stator output' right now. Otherwise - good headlight, bad charge *or* good charging, bad headlight says look other places first.

The photo below of a bad stator shows that the Gyro stator has a single coil for Charge and Headlamp. The charge/lighting coil wires have been cut off and are identified in the photo.

Gyro_Stator_Annotated.jpg (338.83 KiB) Viewed 8418 times

-- Oscilloscope photo --
Here's a Gyro stator with scope probes on the AC stator outputs. Top trace is the Regulator input (20v/div), Bottom trace is the Headlamp drive at 10/div.

Gyro_Stator_Scope_Measurements.jpg (368.1 KiB) Viewed 8418 times

Voltage as measured on the scope for the voltage regulator input is about 44vac peak to peak for the regulator input. The approximate DMM measurement would be approx 1/2 * 44 * 0.707 --> about 15.6 vac. That's 1/2 Peak to Peak voltage * (RMS equivalent (0.707) for a sine wave). Getting back to the original poster's problem, if 15vac or above all is good at the stator. If below 14v or so, and the revs are proper, then check out the stator and it's wiring. Zero ac output can be good. I've had a stator with a cut wire *outside* the engine. Just a splice was needed to fix that problem. The Gyro starter is close to the stator output harness. What happened is the previous owner must have pinched and broken a wire when changing out the starter. Wire damage was inline with the starter mounting ears.


How is the rpm calculated from the scope photo?
One waveform cycle (period) is 2.4 divisions * 5 ms/div = 0.012 seconds. 0.012sec --> 1/0.012 sec = 83.3hz * 60 seconds/minute = 5000 rpm.

[motormike]

Good on ya, mousewheels.....great spread of info to help me with my challenge. The plot thickens with today's addition of Gyro #5 ......Deal included the shop manual... ...that'll eliminate a whole bunch guesswork..... I swear that only one Gyro was the goal when all this began round about Sept.2010......I'll post some pix on the general thread....

[motormike]

Testing on the suspect rect./reg. has revealed all resistance as normal and within limits blah, blah.....of course, the disclaimer made in the manual about wrong tester... ..
...well, ohms are ohms, but I'm still left uncertain. Further action taken has been the installation of a second unit and subsequent test ride..... ......No indication of any problems, i.e.--horn loud, blinkers fast, brake light solid. With second rect./reg. in place, the voltage across battery terminals, running and revved, still reads only 12 on fully charged, new battery. Should be up from that to at least 13v. Suspect is now stator, so I'll run the proper testing in warmer conditions, meantime I ride and do the trial and error thing. ........

[mousewheels]

Yes - your battery when charged sounds to be working effectively Headlight bright as said before is a good sign too, not a perfect stator test, but much better than no/weak headlamp output along with a charge problem...

1) Re: Stator question - set your multimeter to AC and measure the Stator White to Gnd, (Regulator input). Should be the approx 15vac when rev'ed - . If you have good voltage there, look closer at the regulator wiring - inputs and ground connection - including stator ground to battery. Engine and battery neg terminal should be tied together. If voltage is low, check the stator, if absent - see number 2 below, usually the coil will not open internally. All bad stator charge coils I've had (4) have been due to internal shorts.

2) Gyro's route the stator wire harness out of the crankcase where it can get damaged when someone pulls or installs the starter. I had a no power problem where it was just a cut harness where the lower ear of the starter caught a wire. But it did have to cut the outer shielding, black tape, then the wire to cause the fault. Anyhow, a happy and easy find/repair