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cooch
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Joined: 07/14/2012
Posts: 4

Hi all.

I have an electrical problem and I'm not sure where to start, so any guidance would be appreciated!
My 1977 R100RS was showing high voltage (around 14 V) at low revs and would increase as my revs went up, all the way to 16+ volts if I didn't slow down.
I replaced my regulator (and nothing else), and now the voltage will not go over 11 volts no matter how fast I rev.
No generator light comes on and everything works, but...
- the voltmeter pins to the lowest point when I turn on my headlight, but only slightly drops with the turn signals
- my test manual says to start the engine, then disconnect the negative ground strap to do some testing on the regulator, but the engine quits immediately when I do.

Sounds to me like the bike is now running 100% off the battery, but it wasn't before I changed the regulator.
The BMW shop says I have the right one, but I can't do my testing if the bike won't run.

Bike still has points/condenser and is pretty much stock, but I don't know where to start testing and what to test for.

Any advice?

Thanks!

piperjak
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Joined: 04/21/2012
Posts: 7
My Bet ~ Stator

My Bet ~ Stator

schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6546
Yes, battery ignition bikes

Yes, battery ignition bikes need the battery in the circuit to run...not sure why the manual says to remove the negative ground. The bike will run without an alternator but can't run without the battery. Once the battery is dead, the bike won't run at all.

You say gen light comes on...does it also go off when RPMs go over say 1500?

The voltages you're indicating...where are these coming from? Fairing voltmeter or multimeter connected to the battery terminals? The only "true" measurement is the latter.

Have you read Snowbum's article on alternator troubleshooting? Give it a read:

http://bmwmotorcycletech.info/trbleshootALT.htm

I would say repeat the situation with the high voltages you were seeing by actually bypassing the regulator...Snowbum discusses how to do that. Seems to me that if you bypass the regulator and the voltages rise pretty quickly, then it indicates that the alternator and diode board are working correctly. The problem is the regulator. I replaced mine a while back with an aftermarket version - a Transpo IB301 or something like that. I don't think they make it or the number has changed. Is it possible to hook up the regulator wrong? Where did you get the regulator?

Another source for info is Rick Jones at Motorrad Elektrik.

http://www.motoelekt.com/

He has a booklet that is really a must for the old Airheads...Classic Boxer Charging...check under Good Stuff.

I'd be interested to hear more on the above.

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'78 R100/7 '69 R69S '52 R25/2

cooch
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Joined: 07/14/2012
Posts: 4
thanks

Actually, I mentioned that the generator light does not come on, even at a low idle.
It used to come on when I had the old regulator in, but now it does not come on with the new one in.

The peg high and peg low voltages were from the fairing meter, however when I placed a vm on the battery, it reads a constant 11 volts when running at any speed.

I removed the new regulator, and no change: the vm still reads 11 volts and does not flinch with engine speed.
I can't seem to replicate the high voltage anymore, no matter what I do!

Here's the sequence of events:
1) bike voltage shown on fairing meter ran high and would eventually peg at 16+
2) replaced regulator with http://store.bobsbmw.com/product/hella-voltage-regulator---high-output (which they claim is correct)
3) started bike; vm now read 11 volts and would pin to lowest point when I turned lights on
4) gen light does not turn on at any rpm
5) voltage stays 11 volts even after removing new regulator
6) not possible to hook up wrong because it has a 3-prong plug

I will check out the links you provided...thanks!

cooch
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Joined: 07/14/2012
Posts: 4
stator

Could you fill me in a little on how a bad stator would cause what I'm seeing?
Do you think it was OK until I put in the new regulator, and then it immediately went bad ?

thanks

piperjak
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Joined: 04/21/2012
Posts: 7
It happened on my 96 harley.

It happened on my 96 harley. Shop checked output voltage - it was high. THey changed Voltage Regulator and checked it again. Now, voltage was low. Something isnt right?? It turns out, the Stator was bad. (could smell electrical when the cover was removed) THey changed it and all was good. Sounds like the same thing going on ~ just by what you describe. Not a cheap fix on a Harley..!! T

cooch
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Joined: 07/14/2012
Posts: 4
strange

Hmmm...I guess it could happen, but makes no sense to me.

Here's where I am now:

I pulled the diode board out and ran some checks and it checked out OK.
I noticed that 2 of the rubber mounts were busted, but the other 2 were fine.
I cleaned the grounding wires and all terminals, and put it back in.
Some simple resistance checks across the rotor slip rings did not show any problems.
Brushes looked OK so I didn't bother them.

Once all back together, I started the bike and put a meter across the battery terminals as suggested.
Meter reads 13.9 V at around 2000 RPM with no lights on, and around 13.5 V with lights on which is right where I'd expect!
However, fairing meter still reads 11 V at any speed with lights off, and pins to lowest point with lights on.

Guess I'll check voltage at the fairing meter, but not sure what to do if it actually reads that low...

Goomicoo
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Studio City Ca.
Joined: 02/26/2012
Posts: 24
I have the same bike with the

I have the same bike with the same symptoms. As an added bonus my clock stops running with the bike running.
Me thinks there is something going on with the fairing wiring. Voltage at the battery is normal.

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'64 R69s
'66 R60
'67 R69s
'68 R50

RickR90s
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Farmington Hills, MI
Joined: 11/28/2016
Posts: 63
Replace or rebuild the

Replace or rebuild the fairing voltmeter. It's just an indicator. You correctly diagnosed it by placing a voltmeter across the battery terminals.

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RickR90s

Twocams
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VBMWMO #8750
Joined: 03/16/2014
Posts: 696
The volt meter on my 92

The volt meter on my 92 R100RT was doing dumb things. I bought a Equus 2" volt meter ($35?) black face/white #s. Went right in the hole no mods. And how many people are going to say " nice bike" let me look at your volt meter make sure its the right one?
Im sure there is a 2" meter out there with green #s. I stopped looking.

twocams

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Twocams
69 R69S 03 K1200GT
92 R100RT

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