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TOPIC: How to test a alternator rotor?

How to test a alternator rotor? 6 years 6 days ago #452301

  • XL777
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I have read through many posts and read in detail the post on how to diag. the elec. sys issues. I have both the FSM and hayes. I rebuilt my motor last year and put about 500KM on it until one day I lost the 1/2 cyl on my dyna s. The problem related back to low battery caused by no voltage which killed it.

Problem: My battery wont charge above 12V

Items changes/fixed since the problem occurred
1. New Dyna S/Dyna coils, WC mod
2. Traced and cleaned the entire wire harness, double checked ground point on the motor case.
3. Performed the tests as outlined in the FSM on the reg/rec, stator.
4. Results led me to a bad reg/rec, and shorted stator. Stator appeared to have touched rotor as fine shavings were found in the cover and wear marks on stator (bolts slightly lose :() I know this can kill the magnets.
5. Replaced reg/rec, and stator
6. Performed tests again still not outputting 14V at 4K RPM however, voltage does rise .03V at 4K RPM enough to keep it at 12V. All resistance tests are positive.
7. Bike stalls if RPM is raised using the throttle not the choke (not sure if its related)

Since i have replaced the entire system except the rotor this leads me to conclude it has to be it. Other then being broke ha! and furious ha! any other ideas? How can I test the rotor
and any ideas where I can get a new one. Kawai wants $700!!!!

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 6 years 6 days ago #452316

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There is another thread going right now. I mentioned in it that whenever I come across this problem on a KZ (or even Hondas, for that matter), it involves a Dyna S ignition.

The Dyna S uses more power than the stock points, especially at idle, and especially if the 3-ohm coils are used.

If the charging system is marginal, it may work ok on a stock ignition, but the Dyna S just taxes it too much at idle, or even at higher RPMs.

You should load test the output of the alternator to see what you get.

You can do an amperage measurement directly on the output of the rec/reg and see how many amps you get while it's running, but you need an inline gauge that's capable to 30 amps or so. Personally, I don't trust the clamp-on ones. I've seen them be too innacurate at my work.

You can also hook up three 50-watt bulbs to the alternator output wires directly and see what RPM it takes to light them up brightly. Be careful, since the reg/rec won't be hooked up, you may blow the bulbs.

I know these tests sound like a pain in the ass, but it's the only way I can think of to do a load test easily. Open-load tests (the simple ones found in the manual) only give you what the alternator's potential output may be, but not necessarily a good indicator of what it actually puts out. They recommend those tests only because they are easy to do, compared to actual load tests.

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How to test a alternator rotor? 6 years 5 days ago #452339

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I agree with loudhvx on load testing your system. Look in your service manual, it should state the Max Output Rating of your Alternator/ charging system @ a RPM. You can spend some bucks and get a load tester, or cheaply set up a Automotive AMP gauge. I got a cheap, $5 in-dash Amp meter from Harbor Freight Tools i.e. "China Tools". Then some 10 gauge wire and some heavy duty clips. Then you can use it in-line, like loudhvx said, and see if your system is drawing more than charging. All the while keeping a Volt meter across the batt.
Rotor magnets, well I've seen some with drag marks on many things. I'm sure some must get effected by it, but I have yet to see it. The Air Gap between the inside of the Rotor and the Stator needs to be close but not hitting, probably a spec for it but I haven't seen it. Somewhere around .020-.080" would be fairly normal. If it is a huge gap then that would lower the output. The only way I know to test the magnets is to take a metal object, like a 6" socket extension, and see how it is drawn to each magnet. Should be close to the same on all, and hold firmly.
www.harborfreight.com/in-dash-amp-meter-95778.html
Also I have seen but not tried this little tool,
www.harborfreight.com/30-amp-automotive-...it-tester-67724.html
Then here is an actual load tester,
www.harborfreight.com/500-amp-carbon-pil...ad-tester-91129.html

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...

How to test a alternator rotor? 6 years 5 days ago #452406

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Back in school we used a thing called a gauss meter, to measure magnetic field strength, but they cost a fortune bcak then. I wonder if newer technology has made them cheaper now.

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How to test a alternator rotor? 6 years 5 days ago #452442

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I had to Google that one to find out what it was. Measures the Electromagnetic field strength. Looks like the price range varies greatly depending on what you want it to check. Cheap as $12.95, up to several hundred easy enough. But how would you know what level would be correct for say this application, without a known good system to measure against?
Check thi site out for the different meters, www.lessemf.com/gauss.html

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
Last Edit: by Motor Head.

How to test a alternator rotor? 6 years 5 days ago #452443

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Quote

"Since i have replaced the entire system except the rotor this leads me to conclude it has to be it. Other then being broke ha! and furious ha! any other ideas?"
Your bike is a single phase, 2 yellow wires from stator system, right?
One member here, that I know of, has converted to a later 3 phase system from a cheap parts bike he acquired. Got a Stator, Rotor, R/R and harness from the donor. Charging woes fixed, he also had the Dyna S and spent a lot of time/ money to repair stock system. The three phase has a higher AMP output than a stock single phase. I got full loaded output from my 3 phase test basically at any RPM the bike ran at. Although the rated output was @ 4K or something.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...

How to test a alternator rotor? 6 years 5 days ago #452502

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Well I found a load tester but it looks like its just to load test the battery. Dumb question how do I load test the alternator? Do you mean inline by hooking it to the battery (another dumb questions hA!)

I'm going to go through everything this weekend top to bottom to see it I missed anything. Spoke to my buddy an he figures it can't be the magnets very rare.

Could it be that the dyna ign/coils are simply drawing more power and the voltage is not going to register at 14 V?

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 6 years 4 days ago #452562

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Motor Head wrote: I had to Google that one to find out what it was. Measures the Electromagnetic field strength. Looks like the price range varies greatly depending on what you want it to check. Cheap as $12.95, up to several hundred easy enough. But how would you know what level would be correct for say this application, without a known good system to measure against?
Check thi site out for the different meters, www.lessemf.com/gauss.html


It was used to check magnetic field strength, when we used it in school, not electromagnetic field stregth. With the magnet just sitting stationary there should be no electromagnetic field. I don't know what effect RF would have on the gauss reading, but there shouldn't be any when measuring the rotor. It was such an expensive instrument back in the day, I'd be wary of one for $12.95 for accuracy, but I really have not kept up on that equipment technology.

But as you suggested, it would only be useful for A-B comparison rather than looking at the actual level on a particular rotor. It would only let you know if a rotor was good compared to a known good one. I suppose it wouldn't hurt to start collecting data so others could compare against it, but I just don't see everone owning a gauss meter soon, :) (I guess it's also called a magnetometer).

Heat and vibration are some of the fastest ways to reduce a magnets intensity, so with with the scraping marks on his rotor, it's not out of the question for his rotor to be weak.


However, regarding his actual charging problem, I think there may be a wiring issue since he's not getting any significant increase in battery voltage with 4000 RPM, and he replaced stator and reg/rec already. In this case I don't think I'd advise a stator replacement yet. I was originally just answering his question on hot to test a rotor, by using a load test, but I'm not sure that is the correct troublehsooting path at this point, since he is getting nothing out of the stator/reg/rec.

My first place to look would be tracing every wire in the charging system (which he already did) and make sure the Coil-mod is not interfering.


@ XL777;
You should try to make AC voltage measurements on the yellow wires right at the input of the reg/rec while everything is connected and idling, to confirm there is something there. The actual level won't matter since it will not be AC sinewave at that point, as long as it is not close to zero.

Then take a DC measurement at the output wires of the reg/rec (black wire and white/red wire).

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Last Edit: by loudhvx.

How to test a alternator rotor? 6 years 4 days ago #452681

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Ok I went back and re=read your threads. It sounds simple but do you have both a battery cable and a ground wire on the Negative battery terminal. Cable to engine block, starter motor and ignition ground, and a like 14 gauge wire to the frame near the R/R? Just wondering if maybe poor ground could be an issue. R/R grounds to the frame, so a wire from frame to Batt neg should be included.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...

How to test a alternator rotor? 5 years 11 months ago #453914

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Been very busy so I have not had a chance to continue my quest.

I have a combo R/R grounded to the engine along with the negative battery terminal

Are you saying the batter should be ground to the engine and the R/R to the frame?

I did the test with the R/R unplugged should I get a increase in voltage even with the above setup?

Also anyone have an idea as to the voltage drain the dyna coils and ign have on the whole system? I might be chasing 14V for not.

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 5 years 11 months ago #453967

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Unplug only the Brown sense wire, as this is where the R/R would see how much to send back to the battery. Not sure if the Combo R/R you have has the Brown Wire, but I thought you posted that it did.
The Negative battery cable going from the battery to the rear of the motor, also a probably 14 gauge wire from negative battery to frame. R/R should ground to Frame, Black/ Yellow wire.
You should get over 14v across the battery with the brown disconnected. It will try to put full output voltage through to the battery.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...

How to test a alternator rotor? 5 years 11 months ago #454458

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I have a new combo R/R colors are black (ground), brown (sense) and yellow.

All grounds checked. - battery cable to motor, R/R frame, WC mod motor, - battery to frame again!
I downloaded the electro sport fault finding chart (much better then the manual!!) If this isn't my problem then I need to fix it first.

Step 1: Battery fully charged = about 12V
Step 2: at 4K RPM battery still 12V
Step 3: Test: + battery lead and white/red output wire should =/less then 0.2V. Actual 0.3V HIGH suspect bad connection in fuse box.
Step 4: Test: - battery lead and black R/R ground at idle should =/less 0.2V actual 0.1V GOOD[/u.
Step 5: Test: + battery lead and Brown R/R sense wire at idle should be =/less 0.2V with headlight on. Actual 0.66V Very High

It appears that I have a bad fuse box, ignition lead or + battery cable. I pulled the cable no corrosion but I cleaned it anyway. Fuse box shows some sign of melting around white/red 20A fuse all others look ok. According to the fault chart this one is a tough one to find check the entire circuit the R/R isn't getting the correct information and not charging. However, shouldn't I get full voltage readings if I unplug it?

. Could it be related to the WC mod?

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me
Last Edit: by XL777. Reason: typo

How to test a alternator rotor? 5 years 11 months ago #454465

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Yes. 6.6v from battery + to brown at the Reg/rec is a major voltage drop. That needs to be fixed, and is usually due to bad connections at the fuse box (which will also cause the appearance of melting wires at the fuse box). However, as you said, it should result in the voltage being too high at the battery, not too low. Since it's not, this usually means a bad ground, but you checked that. So that is confusing. Have you checked the output of the alternator at the three yellow wires just before they connect at the reg/rec?

Your step 3 test does not indicate a bad fuse box. There are no fuses between the reg/rec output wire and the battery. The connection path should be reg/rec output wire to the battery, or reg/rec output wire to the starter solenoid where it connects to the battery positive cable.

The WC mod would only cause a problem if it is wired improperly, but we can't guess what the mis-wiring would be without knowing exactly how it is wired.

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How to test a alternator rotor? 5 years 11 months ago #454472

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Major drop. This is why I,and others, say the Coil mod is a band aid covering up the real problem. Much better to fix the actual problem.
Any sign of heat at the wires is resistance. Current will not flow freely. A new fuse box may be necessary, but the wiring would also need attention. I believe that would be your Main Fuse, which feeds the ignition switch, then power returns to the Fuse box. Since your charge volts is still lower than it should be, is it from old stiff heated high resistance wires? It sounds like this could be your issue. Those wires from the stator, what condition are they in? They can get in a state as I just described, and voltage loss will be the result.
Go through and check All wiring and connectors, pay close attention to the wire condition at least three inches back from each.
Get it right and Ditch the coil Mod, ;)

Mfolks has a great list of electrical suppliers, here is just 1 source: www.oregonmotorcycleparts.com/connectors.html
Z1 also has connectors.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
Last Edit: by Motor Head.

How to test a alternator rotor? 5 years 11 months ago #454496

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I edited the post it was 0.66V from the + and brown RR. It should be 0.2V according to the flow chart.

I`m going to fix this first and then test. New fuse box and wires.

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 5 years 11 months ago #454539

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Bought some new blade style inline fuses sadly napa didn't have a 3 fuse box grr. I'm going to solder these in in place of the fuse box with new wire and see if that helps.

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 5 years 11 months ago #454542

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Check out this site for some fuse boxes: www.delcity.net/store/8!way-fuse-block/p_10823.a_1
Hows the wires from the stator harness connecting to the R/R? Any sign of heat? Stiff wire near the connectors?
Does your R/R output wire go to the Batt+ terminal or to the solenoid terminal? Check any and all where this circuit travels.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...

How to test a alternator rotor? 5 years 11 months ago #454575

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The stator is new other then the block connector and sensors (oil ,neutral). The r/r is new. Both plug into a junction that appears fine.

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 5 years 11 months ago #454581

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If I was to test the continuity of each of my wires what should it be? I'm thinking of pulling all the charging wires apart again and check each wire at every junction to find shorts.

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2012 Triumph Bonneville SE black

1978 KZ1000 B2 LTD
Fresh top end rebuild
Rebuilt head
Wiseco 1015 pistons
Dyna s
Green Dyna coils
Wired george mod


It is easier to say what I haven't replaced then what I have.

I must love this cruel mistress since she hates me

How to test a alternator rotor? 5 years 11 months ago #454582

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Personally, instead of an OHM check for resistance, I would look for voltage drop while loaded and running at each side of every connector.
Voltage drop under load is a much better test than an OHM meter putting some small current through a circuit.

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1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
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