low voltage showing...whassup?


User avatar
Redplexus
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 14
Joined: Mon Apr 03, 2017 4:06 pm
Location: Reading/Berkshire/UK
Location: Reading/Berkshire/UK

low voltage showing...whassup?

Post by Redplexus »

New to the CBX (Z model, 1979) but keen to understand the beast.

riding with the light on, voltmeter shows not much more than 10V, without the light it crawls back to almost 12V but at no time does it get into the healthy zone.

fearful that I will one day discover that the battery goes flat whilst riding, I'd like to sort it out now, UNLESS the voltmeters are notoriously inaccurate (which I would doubt - never seen that kind of sloppiness from Japan.

suggestions please? is this likely just to be a new set of alternator brushes to sort out? or should I be budgeting for a recondition/replacement alternator?
CBX-Z 79
MV Agusta F4-S 01
Hyperstrada
Ducati Cafe Racer
GL1800 Wing

jnnngs
ICOA Member
ICOA Member
Posts: 420
Joined: Tue Feb 10, 2015 2:05 pm
Location: Hants/UK
Location: Hants/UK

Re: low voltage showing...whassup?

Post by jnnngs »

Hi,

It could be either alternator or the voltage regulator / rectifier.

If the alternator, then could be brushes, the alternator clutch plates, or the stator / rotor windings. You need to take it off bike and take a look.

Paul.

daves79x
ICOA Technical Director
ICOA Technical Director
Posts: 4737
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: low voltage showing...whassup?

Post by daves79x »

Lots of info here about troubleshooting charging systems. Have at it and ask if you have trouble.

Dave

Rick Pope
ICOA Rally Director
ICOA Rally Director
Posts: 2270
Joined: Wed Sep 03, 2003 3:16 pm
Location: Lawrencburg, IN
Location: Lawrenceburg, Indiana

Re: low voltage showing...whassup?

Post by Rick Pope »

Before you start removing parts, check all the connections for corrosion and resistance. The plug to the alternator, behind the right side cover is notorious for being corroded. And yes, the meter is often reading low on these bikes, possibly from voltage drop in the harness.
Rick Pope
Either garage is too small or we have too many bikes. Or Momma's car needs to go outside.

famonteiro
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 6
Joined: Fri Mar 10, 2017 10:00 am
Location: Portugal
Location: Portugal

Re: low voltage showing...whassup?

Post by famonteiro »

Hi, my advice is no worry, my first trip (from the previous owner to my place) I thought battery will falt with volmeter around 11-11,5 volts with light on. After about 200 miles nothing hapened.
It would be fine that generator charge nothing in excess so the battery will not drop acid to the frame.
Ok now we have sealed and gel batteries but not in 1979!

fernando

User avatar
wyly
ICOA Member
ICOA Member
Posts: 1727
Joined: Tue Oct 30, 2007 4:20 pm
Location: calgary alberta canada
Location: Calgary Canada

Re: low voltage showing...whassup?

Post by wyly »

if it's the alternator weigh the options of reconditioning the existing unit vs a conversion alternator(mine is a Kawasaki unit)...the conversion units are better, I bought mine from Tim's it was expensive but a cbx friend told me he's seen other conversions for much less.
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

User avatar
FalldownPhil
ICOA Member
ICOA Member
Posts: 929
Joined: Fri Feb 10, 2006 11:25 pm
Location: Marina Del Rey, CA. USA
Contact:

Re: low voltage showing...whassup?

Post by FalldownPhil »

The voltmeter is notoriously inaccurate. Also, the CBX alternator does not put much out below about
2500 rpm. Before you do anything drastic, check the output going to the battery at 2500 rpm. I suspect
that you may be pleasantly surprised.
Best,
Phil
When you are up to your ass in alligators it is sometimes difficult
to remember that your objective was to drain the swamp !!

jnnngs
ICOA Member
ICOA Member
Posts: 420
Joined: Tue Feb 10, 2015 2:05 pm
Location: Hants/UK
Location: Hants/UK

Re: low voltage showing...whassup?

Post by jnnngs »

Hi,

My simple test for charging is if the Neutral light glows "brighter" as revs hit around 2500rpm as Phil says. If it glows brighter / dimmer as revs rise and fall, then it's probably as good as it's going to get!

Paul.

Larry Zimmer
ICOA Web Post/Pix/Video Archive Mgt
ICOA Web Post/Pix/Video Archive Mgt
Posts: 2195
Joined: Mon Dec 15, 2003 2:32 pm
Location: Brighton, MI
Location: Brighton, Mich
Contact:

Re: low voltage showing...whassup?

Post by Larry Zimmer »

Hi, Red,
First thing you can do to put your mind at ease (OR indicated further work!) is to use an external volt meter to check the voltage at the battery with the engine at approx 2500 rpm. Should read 14 volts +/- a couple tenths. If so, then you know you're OK in the real world. As the others have mentioned, the bike volt meter is known to read low. How low depends upon the corrosion at the various connections as has been mentioned above.
If the reading is low at the battery, the first thing to check is the connector behind the right panel, as Rick mentioned. The least bit of corrosion to the joints in that connector will affect charge. If it has never been maintained, don't be surprised to find that the plastic shows signs of 'softening'! (Sometimes called melting!) Pull that little feller apart and clean the connections well -- both the male and female ends. When you reassemble it, include some dielectric (silicon) grease. If that is not the problem, you'll need to pursue the regulator and alternator. As Dave mentioned, there are many posts in here to search for help on that. And, as Dave said, ask if you don't find what you need. Glad to help.
Larry Zimmer
cbxlarry@sbcglobal.net

User avatar
Redplexus
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 14
Joined: Mon Apr 03, 2017 4:06 pm
Location: Reading/Berkshire/UK
Location: Reading/Berkshire/UK

Re: low voltage showing...whassup?

Post by Redplexus »

thanks for the useful guidance everyone. ages pass and still haven't found the fault - so i'm now limited to about an hour of riding before I know the battery will be too flat to restart the bike - and i'm just not big enough to push that sucker all the way home. SO, can anyone point me in the right direction for a Kawasaki conversion, based in the UK? historic authenticity is one thing, but i'd prefer to ride the bike than just look at it.
CBX-Z 79
MV Agusta F4-S 01
Hyperstrada
Ducati Cafe Racer
GL1800 Wing

daves79x
ICOA Technical Director
ICOA Technical Director
Posts: 4737
Joined: Sun Oct 01, 2006 8:05 am
Location: Knox, PA
Location: Knox, PA

Re: low voltage showing...whassup?

Post by daves79x »

Have you done any troubleshooting on your stock alternator? They are simple to work on and check. Could be anything from worn brushes to a bad rotor, which is very likely. Also a weak spring or bad clutches. Less likely is a bad stator or regulator. Your problem can be easily found and fixed. Running the bike with a bad alternator component can be hard on the other good alternator parts. Repairing your alternator is far cheaper than a conversion.

Dave

steve murdoch icoa #5322
ICOA Member
ICOA Member
Posts: 4068
Joined: Tue Mar 04, 2003 9:12 am
Location: St. Catharines, On. Canada
Location: St. Catharines, On. Canada

Re: low voltage showing...whassup?

Post by steve murdoch icoa #5322 »

Some great info and tips on the CBX alternator, again from Mike Nixon.
Other connected articles at the bottom of the page.
http://www.motorcycleproject.com/text/c ... lutch.html

User avatar
wyly
ICOA Member
ICOA Member
Posts: 1727
Joined: Tue Oct 30, 2007 4:20 pm
Location: calgary alberta canada
Location: Calgary Canada

Re: low voltage showing...whassup?

Post by wyly »

because of my lack mechanical knowledge I found it quicker and easier to install a Tim's conversion...as Dave says it's expensive but it works better than the stock unit ...it's possible your battery has been compromised by the problems you've been having as well...my GS1150 had similar issues last year I ended up replacing the alternator/rec only to be left stranded on the road by a battery(new) failure the next week :think: (and my cel phone battery died the at the same time so I couldn't call for help! :roll: :laughing-rolling: ) ...
CBX a work in progress, still improving...GS1150EFE completed and awaiting modifications.....RD350, remnants in boxes scattered throughout the garage

User avatar
NobleHops
ICOA Member
ICOA Member
Posts: 3867
Joined: Mon Jan 25, 2010 7:17 am
Location: Tucson, Arizona, USA
Location: Tucson, Arizona, USA

Re: low voltage showing...whassup?

Post by NobleHops »

As Dave suggests, servicing the stock alternator is a very doable project for a first timer, and a lot less dosh than springing for a kawa setup. Do some searches for info, you’ll find good write-ups.
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

User avatar
Redplexus
New Member & Happy To Be Here
New Member & Happy To Be Here
Posts: 14
Joined: Mon Apr 03, 2017 4:06 pm
Location: Reading/Berkshire/UK
Location: Reading/Berkshire/UK

Re: low voltage showing...whassup?

Post by Redplexus »

OK, thanks for everyone's input. I can now say I've had the beast in quite small parts and variously cleaned, replaced with NOS, and carried out as many adjustments as i can find reference to, and STILL i get no more than about 11.8V from this alternator. installed new brushes, surgically cleaned all parts, added extra shimming to the alt clutch, refaced and flattened the original concave clutch plates, etch-cleaned all contacts, installed new regulator/rectifier, put in new fuses everywhere......does anyone have any pixie dust to throw on the thing? This could ruin my summer riding. :violin:
CBX-Z 79
MV Agusta F4-S 01
Hyperstrada
Ducati Cafe Racer
GL1800 Wing

Post Reply

Return to “ELECTRICAL: Alternator, Batteries, Headlights, Switches, Tailights, Wiring....”