Posted by paullevichambers on August 31, 2008, 4:16 pm
This is a problem that has out smarted me and an entire motorcycle
repair shop. If you can solve this, you have some serious skills, and
I will be eternally in your debt.
I bought an old 1981 CB750K last year, and have been working on it on
and off since. I originally thought that the alternator was the only
problem, as the stator had crumbled into dust and the brushes were
worn well below the line. I have since then fixed or replaced all of
the units in the charging system, and the battery is receiving a
charge. However, my battery is still going dead. It takes about five
days of riding to town and back, but it happens.
Again, I've had the battery tested, I have a new regulator/rectifier,
I just replaced the stator and brushes, and the battery is receiving
an appropriate charge. What on earth is it that could be making the
battery go dead? Is it something in the ignition system, or the
lighting system, or what? What would draw enough power to kill the
battery after about 150 miles? Could anything mechanical or chemical
be affecting the electrical system?
Posted by . on August 31, 2008, 4:57 pm
On Aug 31, 1:16�pm, paullevichamb...@gmail.com wrote:
> What would draw enough power to kill the
> battery after about 150 miles?
I suppose that you know there is usually a tail light only position on
the ignition switch for parking on the street overnight and you aren't
leaving the key in that position.
You might have a parasitic power drain.
Disconnect the positive lead from the battery and hook an ammeter
between the positive cable and the battery. If the ammeter indicates
current flow with the ignition switch off, you have a parasitic load
draining your power.
If you get indication of a parasitic load with the ignition switch
off, removing the fuses one by one may indicate what circuit is
draining power. Then you can disconnect components one at a time to
see which component is causing the power drain.
The fuse panel will get power from the main fuse when the ignition
switch is on.
The rectifier regulator can be responsible for a very small parasitic
drain through the diodes, but it usually takes a month or two for the
battery to go dead due to diode leakage.
You might try disconnecting the rectifier regulator after riding to
see what happens overnight.
> Could anything mechanical or chemical
> be affecting the electrical system?
It's possible that the alternator rotor is slipping on the end of the
crankshaft.
I actually had that happen on my Suzuki GS1100.
This results in the battery slowly going dead as the alternator cannot
charge it fully, no matter how much excitation field current it gets
from the rectifier regulator.
Try turning the alternator rotor by hand with the transmission in
gear. You shouldn't be able to move the rotor without moving the whole
motorcycle.
Posted by Who Me? on August 31, 2008, 9:01 pm
> Again, I've had the battery tested, I have a new regulator/rectifier,
> I just replaced the stator and brushes, and the battery is receiving
> an appropriate charge.
Krusty covered all that hard stuff......as usual....so I will cover the easy
part:
You got an inept test on the battery and IT IS BAD.
If the battery is truly being charged.....13.8V. or more at 4K rpm or
so.....and there is no drain when the key is off......then there IS no other
choice.
Either the battery is not really "taking" a charge or it is sulfated and is
self-discharging overnight.
Not really mysterious at all. It happens ALL the time; both bad batteries
AND inept tests. ;-)
Posted by CS on August 31, 2008, 9:48 pm
> This is a problem that has out smarted me and an entire motorcycle
> repair shop. If you can solve this, you have some serious skills, and
> I will be eternally in your debt.
> I bought an old 1981 CB750K last year, and have been working on it on
> and off since. I originally thought that the alternator was the only
> problem, as the stator had crumbled into dust and the brushes were
> worn well below the line. I have since then fixed or replaced all of
> the units in the charging system, and the battery is receiving a
> charge. However, my battery is still going dead. It takes about five
> days of riding to town and back, but it happens.
> Again, I've had the battery tested, I have a new regulator/rectifier,
> I just replaced the stator and brushes, and the battery is receiving
> an appropriate charge. What on earth is it that could be making the
> battery go dead? Is it something in the ignition system, or the
> lighting system, or what? What would draw enough power to kill the
> battery after about 150 miles? Could anything mechanical or chemical
> be affecting the electrical system?
The other poster gave great info, but how are you testing the charging
system? If riding to town and back is something like 10 miles or so each
way, and if the battery is receiving a charge on a regular basis, even a
constant drain on the battery shouldn't kill it. With the ignition off,
take your voltmeter and check the voltage of the battery. It should be
somewhere around 12 volts after being charged. With the bike running (in
neutral, I hope) check the voltage again. It should read at least 14 to
14.5 volts. If not, the battery is not receiving a charge.
If your bike is anything like the other 30ish old bikes I've seen, which is
to say, neglected outside for months/years at a time playing host to
spiders, birds, and small mammals, you want to take a long, careful and
complete tour of the wiring bundles, connectors, and fuse boxes. Crud tends
to accumilate in odd places, and you'll scratch your head into a frenzy if
you try thinking about how it got there. You'll want to Carefully
disconnect the connectors and fuses, spray some cleaner around, let it dry,
then Carefully replace connectors and fuses. You want to do this Carefully,
because the sun and elements are unkind to small, plastic thingies, so they
tend to break easily.
You can get electronics cleaner at stores that cater to ultra-nerdy
electronics hobbyists. I'm quite sure more practical folks here have a
better solution to cleaning dirty, corroded, crud-caked electrical
connectors that are held together by plastic doodads that may or may not
crumble in your hand, so hopefully they'll chime in sometime in the next
month or two. heh
CS
Posted by ian field on September 1, 2008, 1:19 pm
>> This is a problem that has out smarted me and an entire motorcycle
>> repair shop. If you can solve this, you have some serious skills, and
>> I will be eternally in your debt.
>>
>> I bought an old 1981 CB750K last year, and have been working on it on
>> and off since. I originally thought that the alternator was the only
>> problem, as the stator had crumbled into dust and the brushes were
>> worn well below the line. I have since then fixed or replaced all of
>> the units in the charging system, and the battery is receiving a
>> charge. However, my battery is still going dead. It takes about five
>> days of riding to town and back, but it happens.
>>
>> Again, I've had the battery tested, I have a new regulator/rectifier,
>> I just replaced the stator and brushes, and the battery is receiving
>> an appropriate charge. What on earth is it that could be making the
>> battery go dead? Is it something in the ignition system, or the
>> lighting system, or what? What would draw enough power to kill the
>> battery after about 150 miles? Could anything mechanical or chemical
>> be affecting the electrical system?
> The other poster gave great info, but how are you testing the charging
> system? If riding to town and back is something like 10 miles or so each
> way, and if the battery is receiving a charge on a regular basis, even a
> constant drain on the battery shouldn't kill it. With the ignition off,
> take your voltmeter and check the voltage of the battery. It should be
> somewhere around 12 volts after being charged. With the bike running (in
> neutral, I hope) check the voltage again. It should read at least 14 to
> 14.5 volts. If not, the battery is not receiving a charge.
> If your bike is anything like the other 30ish old bikes I've seen, which
> is to say, neglected outside for months/years at a time playing host to
> spiders, birds, and small mammals, you want to take a long, careful and
> complete tour of the wiring bundles, connectors, and fuse boxes. Crud
> tends to accumilate in odd places, and you'll scratch your head into a
> frenzy if you try thinking about how it got there. You'll want to
> Carefully disconnect the connectors and fuses, spray some cleaner around,
> let it dry, then Carefully replace connectors and fuses. You want to do
> this Carefully, because the sun and elements are unkind to small, plastic
> thingies, so they tend to break easily.
> You can get electronics cleaner at stores that cater to ultra-nerdy
> electronics hobbyists. I'm quite sure more practical folks here have a
> better solution to cleaning dirty, corroded, crud-caked electrical
> connectors that are held together by plastic doodads that may or may not
> crumble in your hand, so hopefully they'll chime in sometime in the next
> month or two. heh
> CS
Why go to the expense of electronics switch cleaner?!
WD40 or similar will do just as good, I used GT85 which is similar but
contains PTFE on my ignition switch - I feared the PTFE might not be such a
good idea but it completely cured the intermittent sidelight supply contact.
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> battery after about 150 miles?