No dash lights, then engine died

[Groover]

Stator. Received the used parts today, and all works. Charges at 14.4v.


Old stator has discrepancy between the 3 leads. 1 combination read .7 ohms, 1 read .8 ohms, and 1 read 1 ohm. The "new" reads .8 between all combinations.


I never did flash the rotor as suggested (was going to be a next step.


This thread basically covered 3 issues, which still leaves it a mystery to me why the bike stalled and battery was completely dead when the rotor failed.


Synopsis: ran the bike hard on highway, on exit ramp at first light, bike stalled, dash lights all out (probably completely shorted or dead battery), next day, bike started, charging light out and not charging, replaced rotor, bike worked for almost a full riding day, stopped to get something to eat, battery charge light stayed on, no longer charging. Replaced stator, and all good now.


Thank you all the help and trouble-shooting along. I hope this helps someone in the future.


Side note, the used parts came with an other rotor (which I did not use) looked to be rewound, ohms on that were 4.4, mine and I believe typical read 3.3-ish. - what would a higher resistance rotor yield? I don't plan on using it, just curious.

[blackcat]

Congratulations, always a good feeling when you finally solve a mystery charging problem.

[chuck peterson]

When the rotor fails, there isn’t any additional needed volts added to your battery to replace what you’re using running down the road…..keeping it about at least 12.3-12.4 at rest..

no water flowing across the water wheel so to speak

All your electric usage (coils, lights, turn signals, radar, cb radio, coffee maker) while running starts to slowly deplete the battery lower and lower until boop! Your battery is below a usable limit and you have become an electrician on the side of the road….

There is a solution Ive heard, of making your way home by stopping at Walmert and replacing the newly purchased battery every stop….

Glad you found the problem…next is a diode board…add another ground there to the transmission

Then a voltage regulator..adjustab le

Then the yellow 3 wire harness…

Then the brushes..

I can’t really complain about the system when Ive never ridden any other bikes that far…

[Groover]

Time for an update, the saga somewhat continues - battery charges, but barely.

Symptoms:

Engine, Cold - Dash light Red for maybe a mile or so, will stay that way until I rev it up to say 4k+ rpm once, then it operates normally after that - still would prefer it to go off a little sooner, but I think that is the regulator, so I plan on swapping that with the older one as I think it made the light go off at a lower RPM in general - both the old and the new one are the EnDuraLast adjustable version - I could try to adjust it, but I can't get to it so I might as well put the old one back on once I take the tank off as it seemed to work better for my riding style and location (mostly stop and go) https://www.euromotoelectrics.com/product-p/vr-extadj.htm

I never did replace the diode board, but I also have an old good one (I think, tested OK) one on hand if needed. All connections are clean.

All seems to work, but that first part where I need to ride it a bit, then sort of make it kick in with a burst of throttle is weird - what would that be? What's really odd and what got me is that I rode it the other day quite a bit, never did give it the 'burst rev" for the dash light to go off (and start this odd charging cycle), and it killed the battery. Luckily I had the jump starter that I've been carrying around, got it started, then rode it a little harder, battery charged, back in business.

The behavior is pretty consistent so now I know how to work it reliably so to speak, but what would cause the delayed start on the charging system? Is that a symptom of a failing rectifier?

Wanted to also add that when I start it from say sitting overnight, I can rev it till the engine blows and it never makes the light go out and start the charging, seems the engine (or diode board? or Rectifier?) need to heat up a bit first before working.

I like to fix things the hard way and drag them on forever as you can see, plus, figured those involved in this were waiting for a new episode anyway :-)

Thoughts on symptoms of a failing diode board?

[n3303j]

My "idiot" Light goes out at 2,000 RPM and is pretty much out unless I get stopped around 700 RPM.

Did you confirm that each brush spring is wound 3/4 turn from relaxed when seated on the brush and each brush is moving freely in its holder and there is no binding at the pigtail wire.

The brush spring can be installed in two positions 180° different. The system will function with either installation. It will be unreliable with 1/4 turn preload on the spring. It needs 3/4 turn on the spring.

Just pull the front cover and lift the spring off the front brush. Let it relax foreward of the holder and be sure it is 3/4 turn beyond "working" position. (Then assume the rear spring is the same). If you only get 1/4 turn to relaxed pull the spring and rotate it 180° to correct placement.

[Groover]

Thanks again, will try that this weekend. I never checked on the replacement stator when I got it.

[Tkelly]

Try a new diode board,is the one in there the original?

[testa_di_formaggio]

Throwing parts at a charging issue, and hoping something will stick, is using a shotgun to kill an ant. You will miss. The function of the various components is quantifiable, a volt/ohm meter is your friend. Find the issue. Measure twice, cut once. Also, there are parts changers are then there are mechanics. Grounds, grounds, grounds.

TF

[Kiwi_Roy]

Many of the old alternators relied on the current through the charge light to provide the initial rotor magnetism, if the bulb was burnt out they might not start to charge.

[Groover]

Just wanted to follow-up on this, has been a while. All checked out OK with the springs, and all seems to be working normally it seems. Still would like the charging to be stronger, so I may upgrade the Alternator to something better some day - as far as the issue goes, best I can think of is that the old brushes needed to settle in with the new rotor - not sure, but all seems to be working now and it was a gradual improvement.

[Bulldog9]

Stator. Received the used parts today, and all works. Charges at 14.4v.


Old stator has discrepancy between the 3 leads. 1 combination read .7 ohms, 1 read .8 ohms, and 1 read 1 ohm. The "new" reads .8 between all combinations.


I never did flash the rotor as suggested (was going to be a next step.


This thread basically covered 3 issues, which still leaves it a mystery to me why the bike stalled and battery was completely dead when the rotor failed.


Synopsis: ran the bike hard on highway, on exit ramp at first light, bike stalled, dash lights all out (probably completely shorted or dead battery), next day, bike started, charging light out and not charging, replaced rotor, bike worked for almost a full riding day, stopped to get something to eat, battery charge light stayed on, no longer charging. Replaced stator, and all good now.


Thank you all the help and trouble-shooting along. I hope this helps someone in the future.


Side note, the used parts came with an other rotor (which I did not use) looked to be rewound, ohms on that were 4.4, mine and I believe typical read 3.3-ish. - what would a higher resistance rotor yield? I don't plan on using it, just curious.

Glad you are all sorted. This was a good thread and troubleshooting for others in the future.

[Kiwi_Roy]

I looked for a 81 G5 on greg Benders Thisoldtractor site
All I could find was this 1978G5 showing a typical Bosh alternator
https://www.thisoldtractor.com/guzzi007/schematics/1978_G5.gif
These alternators rely on the alternator dash light to excite the alternator
they also have a miserable set of fuses which lose contact over the years.

Pull esch fuse and rub the contacts at each end on your jeans to polish them up
bend the spring clips to create more tension and smear the contacts with Vaseline so they don't corrode
Take the cover off the fuse box and measure for Voltage at the fuse terminals, it should read 12 Volts in relation to the chassis
Some of the fuses will require the key to be in On position
1978 or 1981 this bike is getting a bit old in the tooth, Guzzi Electrics was never the best.
Motto Guzzi, making Electricians out of riders since 1921