Dropped side cover, now she won't charge

[freddy3]

The bike was running great until I dropped the side engine cover as I was R&R'ing the clutch cable (although I did not see/hear it, the cover may have tapped the rotor as it fell?). After replacing the cable, the battery won't charge.

Any suggestions as to the most likely cause for the charging system to quit like that?

The rotor and brushes/wires look fine (nothing dirty, loose or broken). Fuse is also fine (I replaced it just to be sure).

I've got an LED charging system gauge on the bike that normally sits steadily in the green at idle (~12.5V~13V) and increases further into green (~14V) as RPMs increase. Since this happened, the charging gauge now sits in the yellow (~11V) at idle and stays there even as RPMs increase. So I know the alternator's not outputting and the system's running off the [new, fully-charged lithium] battery. If I turn on the headlight, the charging gauge will slowly fall into the red (~10V) and begin flashing, indicating the system voltage is dangerously low (below ~9V and falling).

Unfortunately, I'm very limited in my ability to perform tests or major disassembly because I live in an apartment and am prohibited from working on vehicles in the parking lot. I don't know anyone nearby with a garage, so I'm hoping someone may be able to direct me to THE component that's likely to be the problem. Or, at least a simple (voltmeter) test to locate it.

 

[nj1639]

Try a slap test to see if the rotor creates a magnetic draw, no disassembly required.

 

[freddy3]

Try a slap test to see if the rotor creates a magnetic draw, no disassembly required.

Thank you!
It's been awhile since I've done any electrical work on the bike. Is the "slap test" where I hold a wrench within 1/2" of the alternator cover and turn the ignition to ON to see if the wrench is drawn inward to the cover?

 

[Adamc]

Thank you!
It's been awhile since I've done any electrical work on the bike. Is the "slap test" where I hold a wrench within 1/2" of the alternator cover and turn the ignition to ON to see if the wrench is drawn inward to the cover?

Yes you are correct.

 

[freddy3]

Yes you are correct.

Then I'll give that a try and report back this evening.
Thank you!

 

[Rasputin]

Take the cover back off and see if that cures it. Sounds like a trapped wire.

 

[freddy3]

Take the cover back off and see if that cures it. Sounds like a trapped wire.

That was the first thing I did. Wires're fine. Thanks.

 

[freddy3]

Update: No effect on steel screwdriver or two wrenches when held next to the alternator cover (front or either side) and the ignition was switched on and off and on and off....

So, does the lack of any magnetic field with ignition switched to ON indicate a duff rotor/alternator?

 

[nj1639]

That's what it sounds like.
Next step is to ohm slipping to slipring on the rotor, looking for around 5 ohms. Brushes should not be touching the slip rings when this is done.

 

[freddy3]

That's what it sounds like.
Next step is to ohm slipping to slipring on the rotor, looking for around 5 ohms. Brushes should not be touching the slip rings when this is done.

So, first, I have to remove both brushes and, then, test resistance from one slipring to the other slipring. Correct?
Do I also need test each slipring to the rotor's core??

If I remember correctly, the rotor's just a single (coiled) wire running inside the rotor from one slipring to the other. How that wire could've gotten broken or shorted while I R&R'd the clutch cable (even, considering the possibility that it got dinged when the engine cover fell a few inches) really doesn't make sense??

 

[nj1639]

Just test slipring to slipring. If it passes muster then you've eliminated it as a problem, though failing the slap test points in that direction and it's one sure way to find out.

 

[freddy3]

Just test slipring to slipring. If it passes muster then you've eliminated it as a problem, though failing the slap test points in that direction and it's one sure way to find out.

Okay, I'll try to test it tomorrow evening. Thanks again!

 

[freddy3]

Update: Based on my limited testing, I think I may have a dead stator.

Rotor:
Although it often varies, the rotor slipring-to-slipring resistance measurements did hit the 5~7 ohm target.

I was able to take the following additional measurements before the property mgnt read me the riot act...

Rectifier:
Black Fluke probe (set for resistance) to black contact in rectifier connector and red Fluke probe to each of the white wires = 1.7M ohms.
Reverse: Red Fluke probe to black contact in connector and black Fluke probe to each of the white wires = 2.06M ohms, 1.72M and 1.86M.

Stator:
Resistance between each of the 3 white wires = .8 ohms ~1.0 ohms.
Any of the white wires to stator housing = ~10 ohms.
Note: I happen to have an extra NOS stator and I get same readings between each of the white wires, but I get INFINITE resistance between any of the whites and the stator housing. However, because the NOS stator is out of the bike, I don't know if that makes any difference???

What do you think?

 

[nj1639]

I haven't had the need to test stators yet, though there are posted processes for doing such.....thinking my Haynes manual has the specs.
Appears the rotor test passes save for the 2ohm fluctuation. Were you holding your tongue right?

 

[freddy3]

Were you holding your tongue right?

It was dark, so hard to tell..

 

[freddy3]

Update: I replaced the stator, but no change. In fact, once the stator was installed, I re-ran all of the electrical tests it passed out of the bike....but now they mirror the original stator. That is, there's supposed to be infinite resistance between the three white wires at the connector and the stator housing, which there was when the stator was out of the bike. Now, there's about 10 ohms resistance, the same as the stator I just removed. So I'm stumped again..

 

[jpdevol]

I tend to think (as the stators are rarely the problem) and both test the same, that the problem is elsewhere....If you're not getting magnetism, The rotor is faulty or not being energized. Do the rotor tests and check to see that the brushes are getting both power and ground - go from there. If you can get magnetism, then the output of the stator can then be verified.

 

[Jim]

There's a tiny pin and slot arrangement on the stator and engine case. If it's not slotted in, the stator will rub on the rotor. Did you make sure it's properly slotted?

 

[freddy3]

If you're not getting magnetism, The rotor is faulty or not being energized. Do the rotor tests and check to see that the brushes are getting both power and ground - go from there. If you can get magnetism, then the output of the stator can then be verified.

There are only two tests for the rotor -- resistance between the two rings and resistance between each ring and the rotor's core. All check out. Still, it flunks the wrench test (no magnetism).

 

[freddy3]

There's a tiny pin and slot arrangement on the stator and engine case. If it's not slotted in, the stator will rub on the rotor. Did you make sure it's properly slotted?

That pin's on the rotor shaft, which I haven't removed. So I can't imagine it's slipping. And it'd have to be slipping 100% to produce 0 output, which is what I'm getting. Or, not getting.