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Author Topic: cb750a alternator.  (Read 23810 times)

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Offline MCRider

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Re: cb750a alternator.
« Reply #25 on: December 06, 2010, 06:32:40 PM »
True, rare circumstance, but it does happen. I mentioned in the thread of Andy's electrical problem I've had 2 in my life. A shorted out starter button (too aggressive pulling the wires through the bars stretched out the connection in the switch housing), and... a failed stator.

Since failures are so rare, I'd have little problem buying one from ebay. There are new ones available in the $140-$175 range. Though I'm still looking for the source i had at one time.

Still, no current from the alternator doesn't point only to a bad stator.
« Last Edit: December 06, 2010, 06:36:47 PM by MCRider »
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Offline TwoTired

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Re: cb750a alternator.
« Reply #26 on: December 06, 2010, 06:34:31 PM »
Quote from: maliveline on December 06, 2010, 06:27:24 PM
well the guy checked it and said there was no current comming from the stator to the rectifier and he said it was a bad stator so w/e

Sounds like he doesn't know WTF he is doing then.  A bad field coil makes no magnetic field.  No magnetic field makes no stator output.  Was he assuming it was a permanent magnet alternator like modern bikes have?




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Offline MCRider

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Re: cb750a alternator.
« Reply #27 on: December 06, 2010, 06:40:10 PM »
Are you close to indy? Either way, I'll loan you a good stator if that's what it takes to narrow it down. I also have extra field coils. Ultimately I'd need a little coin for either. But in the meantime, you just pay the freight.

PS: Dang i just realized you have a CB750A. I think that stator is unique to the As? Don't know about the field coils. Or maybe its the field coil that's unique? I tried.
« Last Edit: December 06, 2010, 06:49:27 PM by MCRider »
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Offline maliveline

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Re: cb750a alternator.
« Reply #28 on: December 06, 2010, 07:51:37 PM »
that dude was saying that if it was the field coil going bad that you would still get a little bit of current out of the alternator but if it was the stator you would get no current at all which is what he was getting. either way I already ordered a stator off hondapartsnation.com like a dumbass because they charge a 25% restocking fee and now im all stressed out and i cant decide if i want to cancel my order or not.
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Offline maliveline

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Re: cb750a alternator.
« Reply #29 on: December 06, 2010, 08:09:28 PM »
what should i do? this bike is gonna give me a stress related heart attack!!!
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Offline Spanner 1

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Re: cb750a alternator.
« Reply #30 on: December 06, 2010, 08:44:57 PM »
What should you do ?... do the tests like all the responders asked u to do. Have you voltage to the Field coil ?... haven't seen where you state that there is or not, well ?... No charging unless voltage to the field, a very simple and basic test you can do with a 12v bulb, don't even need a meter. Let's start there.
Put your meter on DC Volts ( lowest setting above 12v, like 50v or 100v, whatever it has ). Start the bike , put the black meter wire to ground/ engine case/ battery NEG. ( your choice ) and the red meter lead first to the black wire on the regulator ( do not disconnect anything ) What does it read ?... then put the red lead to the white wire on the regulator, what's the reading ?... report back por favor ...... or send it back to the bike shop, your call  ;D ;)
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Offline TwoTired

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Re: cb750a alternator.
« Reply #31 on: December 06, 2010, 10:38:00 PM »
Quote from: maliveline on December 05, 2010, 09:30:42 PM
Then I plugged my tester wires into the green and white wires that plug into my voltage regulator and i was getting a reading of .3 ohms to .5 ohms depending on how I hooked up the test wires again switching around black and red. Then I hooked a test wire up to the white wire and touched the other test wire to the alternator cover and I got .3 ohms as well.
If you measured the field coil correctly, the data shows the field coil to be shorted.
If shorted, it can't make magnetic field.

With no magnetic field, the stator will produce no (that's zero) output whether it has a fault or is brand new perfect.
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Offline maliveline

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Re: cb750a alternator.
« Reply #32 on: December 06, 2010, 11:21:58 PM »
I'm pretty sure I measured the field coil correctly. the only thing that could make me think that I measured it incorrectly if there was something wrong with the wires in the bike. I'm thinking about seeing if I can change my parts order tomorrow from a stator to a field coil. If the are going to penalize me for chaning my order I'm just going to cancel the damm order and take the 25% restocking fee as a loss and my bike will rot before i will ever buy another part from those cock suckers again. either way spanner, I'm planning on doing your voltage test tomorrow when I get my bike back from that half assed bike mechanic. I will post more data tomorrow.
« Last Edit: December 06, 2010, 11:25:58 PM by maliveline »
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: cb750a alternator.
« Reply #33 on: December 07, 2010, 10:11:33 AM »
Watch what field coil you get. The A is specific. Thicker wire, less resistance, more output. You can visually go by the gauge of the wire if you have both - it's thicker - or go by the code that is stamped on the end of the coil if you are buying sight unseen. The A field coil I have is stamped LD120-01 and the F/K is stamped LD113-01.

The best I can tell visually the stator coils are the same and by testing they are the same. 
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Offline Mark M

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Re: cb750a alternator.
« Reply #34 on: December 07, 2010, 10:21:53 AM »
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Offline maliveline

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Re: cb750a alternator.
« Reply #35 on: December 07, 2010, 10:58:59 AM »
http://www.hondapartsnation.com/pages/parts/viewbybrand/7/Honda.aspx

this is where I bought my field coil from...

it gave me to choose the 76 CB750A with the VIN# CB750A-7000001 TO CB750A-7007331
 
and my vin# cb750a7003712 so I figured it shoud work.
« Last Edit: December 07, 2010, 11:01:14 AM by maliveline »
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Offline maliveline

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Voltage to the field coil
« Reply #36 on: December 07, 2010, 01:46:43 PM »
well I performed the test which you described spanner and heres what I got.

I hooked the black wire from my multimeter to the negative terminal on my battery.

Then I hooked up the red wire from my multimeter to the white wire on my voltage regulator and I was getting about 10.7 volts

Then I hooked up the red wire from my multimeter to the black wire on my voltage regulator and I was getting about 10.7 volts as well.
'
I went for a short ride earlier when I brought my bike home from the mechanic so I figure this must be why I was getting less that 11 volts because my battery was probably drained during the ride.

if could you walk me through some more tests please I would greatly appreciate it.

I really think I'm starting to narrow things down to components in the alternator though, and I have a field coil being shipped to me with in a few weeks
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Offline Spanner 1

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Re: cb750a alternator.
« Reply #37 on: December 07, 2010, 02:26:07 PM »
Well at least your regulator is passing voltage to the field coil ( on the white wire ). Very next thing to do would be to have a close look at the big 2-part connector that goes to the alternator. It's got 3 x yellow wires a white and a green. Are both halves all the way 'home' or is there any corrosion or blackened connection or is the connector 'bulged ( by heat ) and not mated properly ?
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Offline maliveline

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Re: cb750a alternator.
« Reply #38 on: December 08, 2010, 10:44:48 AM »
I see 2 big wires that come out from just a couple of inches away from the shifter cover right next to the alternator.

One of the wires goes to a connecter at about the center of the bike. It has 3 yellow wires a black wire a green wire and a white wire. It appears to be connected just fine.

is this the right connector?
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Offline TwoTired

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Re: cb750a alternator.
« Reply #39 on: December 08, 2010, 11:39:32 AM »
Take that connector apart and measure the white a green wires for resistance.
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Offline maliveline

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Re: cb750a alternator.
« Reply #40 on: December 08, 2010, 01:48:00 PM »
I measured the white and green wires that are comming out of the alternator and I got 0 ohms.
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Offline TwoTired

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Re: cb750a alternator.
« Reply #41 on: December 08, 2010, 02:54:00 PM »
Just to be clear, there is a big difference between Zero ohms and infinite ohms.

Also were those the wires going to the alternator, or the wires going to the Vreg.  Or which half of the connector terminals did you measure.


If you are sticking with the zero ohms to the field coil, either it's windings or the leads going to the filed coil are shorted to the engine case.

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Lloyd... (SOHC4 #11 Original Mail List)
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Offline maliveline

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Re: cb750a alternator.
« Reply #42 on: December 08, 2010, 04:58:34 PM »
the wires I measured were going to the alternator. I'm not sure if it was infinite ohms or zero ohms. i touched my tester leads to the green and white wire and my meter was reading zero like i didn't have it hooked up to anything or something. I can take pictures tomorrow if you want to see.
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Offline TwoTired

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Re: cb750a alternator.
« Reply #43 on: December 08, 2010, 05:10:42 PM »
If the reading was the same as when the probes are unconnected, that's infinity, no connection, or electrical path between them.

You'll have to take things apart to physically and electrically get closer to the actual field coil windings.  Might just have a broken/loose connector inside there.
I've not taken a 750 A apart there.  So, I can't give details.  I just know how the charging system is supposed to work.

Cheers,
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Offline maliveline

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Re: cb750a alternator.
« Reply #44 on: December 08, 2010, 05:27:41 PM »
oh i can get things apart. So should i take everything apart and then check for resistance on the 2 wires that hook up to my field coil next?
assuming that i dont find any loose connectors...
« Last Edit: December 08, 2010, 05:37:02 PM by maliveline »
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Offline TwoTired

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Re: cb750a alternator.
« Reply #45 on: December 08, 2010, 09:52:37 PM »
You need to know if the field coil winding itself has a broken internal connection.
Probably have to take it off for that.  But as I said, intimate details of the 750A specifics, i don't know.  Post pictures. If I can see the arrangement, I can better advise.

Spanner had a a 750A he might know better of the specifics, without pictures.

Cheers,
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Offline andy750

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Re: cb750a alternator.
« Reply #46 on: December 09, 2010, 04:38:55 AM »

Have you verified that the rectifier and regulator are working?

The rectifier as mentioned already in this thread is much prone to go bad. Might save you a whole lot of time working on the alternator - which rarely goes bad unless the issue is the wiring coming from the alternator - I assume you have checked that is ok? Mine was frayed at the ground wire (located under the gear cover) and this is why my battery was not charging. On another bike the cause was the rectifier.

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Offline Spanner 1

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Re: cb750a alternator.
« Reply #47 on: December 09, 2010, 06:44:08 AM »
That eyeball thing is very distracting   :o ;D..... anyway, there is one more connection on the field coil / alternator wires and it is under the shifter cover, as Andy describes. There are 9 screws to remove ( and the shifter of course ). Be real careful of the gasket and the 2 locating 'dowels' . Under here is 3 bullet connectors on the yellow wires and 2 bullets on the white and green... hopefully the problem is a disconnected wire........ put your meter on the green and white wires, you will have to clean 'em up first as they will be oily.
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Offline TwoTired

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Re: cb750a alternator.
« Reply #48 on: December 09, 2010, 10:12:38 AM »
Quote from: Spanner 1 on December 09, 2010, 06:44:08 AM
That eyeball thing is very distracting   :o ;D.....

Is it?  Guess another one is in order...
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Offline maliveline

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Re: cb750a alternator.
« Reply #49 on: December 09, 2010, 11:46:05 AM »
Ok I got the shifter cover off. I started looking around in there and guess what. One of the 2 wires coming from my field coil was disconnected....

the only problem is all my connectors are pretty oily and nasty and the plastic wrap around the connectors is totally degrading and everything is very loose.

Also I virtually have no slack at all on the wires that are deep inside the shifter case. I dont even know where to begin to go about fixing this problem.
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