Posted by paul c on May 18, 2010, 12:21 pm
pokee joe wrote:
>
>> A lesson I've re-learned a number of times on bikes and cars: Even
>> a little six-inch ground strap when the ends are corroded/oxydized
>> or even thinned due to use might have as much as a quarter-ohm
>> resistance. A 300 watt starter motor has a resistance of less than
>> half an ohm. In that case, a 12 V battery would lose a third of
>> its voltage, ie., 4 V on the ground strap, leaving only 8 V max for
>> the starter.
>
> Actually, it's a lot worse than that. Even small starter motors will
> draw a locked rotor current of 100 amps or more. That means the
> resistance of the starter windings is around .1 ohms and it's not
> unusual for larger two cylinder engines to have starters that have
> less than .04 ohms. Your 300 watt starter will draw more than 150 amps
> initially and have a resistance of less than .075 ohms. That's why we
> require starting batteries in the first place, they are specifically
> made to provide far higher short term current than deep cycle
> batteries.
> ...
Nice points. Makes sense that the initial huge current and the steady
current would bypass the main fuse.
Straying a little, I noticed the wiring diagram for a little S65 at
http://oldmanhonda.com/MC/WiringDiagrams/MCwiring.php#class
shows negative ground and the main fuse is on the negative side, unlike
most others I've seen where the fuse is on the positive side of the
battery. Not sure why this was done.
Posted by . on May 15, 2010, 2:55 pm
> Now it wont strat at all. All I get each time I hear the solenoid (once
> each time I press the starter).
Check all the electrical connections and fuzes.
Also, check the starter circuit interlock switches on the clutch and
sidestand.
Sidestand switches cause a lot of problems in damp riding
conditions...
If there is corrosion on the terminals at the battery, that makes high
resistance and the starter won't get enough "juice" to crank the
engine.
> I think the battery is fine as I have fully charged it and the charger shows
> it as being full.
Automatic chargers will shut off to protect themselves even before the
battery is charged if they sense that the battery is taking too much
current,
Maintenance-free batteries will last for 6 to 8 years without much
attention, and you're at the 8 year mark now.
One indication that a maintenance-free battery has reached the end of
its useful life is that the sides of the plastic case bulge out or are
sucked in, giving the impression of a starved horse with its ribs
sticking out.
Another indication that a maintenance-free battery has lost its water
is white powder around the terminals.
> Also, the headlight work fine.
Got a voltmeter?
If you turn the headlight on, it should stay bright for at least half
an hour without the battery voltage dropping below 12 volts.
> Also, can I jump start a bike from a car battery - just to be 100% sure it
> isn't the battery.
Yes, it's possible to jump start a motorcycle from a car battery. If
the starter cranks the engine, just don't keep cranking endlessly for
a minute at a time because the starter will get too hot.
And motorcycle starters are very expensive if you have to buy a new
one.
The starter solenoid is called a "magnetic switch".
http://webservices.motorsportdealers.com/parts/partImages/HOM/2/14MBWX/ILLU=
ST/MBW4F/2701A.Gif
Notice that there are two blade type fuzes on the solenoid. Check
them. If they blow out, the motorcycle won't run.
After cleaning the terminals and checking the fuzes, you can try
jumpering across the two large terminals on the solenoid.
If the battery is good and the terminals are clean and the starter
still won't turn the engine at all, the only possibilities left are
worn out starter brushes or a bad
starter armature.
Posted by S'mee on May 15, 2010, 10:59 pm
Oh piss off it's blatantly the battery you senile bastard son of a
seventh fleet deserter.
Posted by . on May 15, 2010, 11:54 pm
> Oh piss off it's blatantly the battery you senile bastard son of a
> seventh fleet deserter.
Suck my balls, you okie goat roper.
Posted by No Spam on May 16, 2010, 1:23 pm
:
>
> If you turn the headlight on, it should stay bright for at least
> half an hour without the battery voltage dropping below 12 volts.
>
Actually, that's not such a good idea. While the bike isn't old enough
to have points you could burn by leaving the ignition on that long, and
it isn't old enough to have a ballast resistor that you could overheat
and ruin by leaving the ignition on that long, still it's not a good
idea to leave it turned on that long while the engine isn't running.
Yes, your electronic ignition should have good enough protection
circuitry to keep from damaging it, but it's designed to handle voltage
spikes on the signal lines, not continuous current if the crankshaft
just happened to stop in exactly the wrong spot the last time you shut
the engine off.
That kind of test will tell you the battery had at least 3 amp hours of
charge when you were trying to start the bike. It won't tell you if the
battery has low enough internal resistance, to supply the starter with
enough current, to crank the engine over fast enough to start. To find
that out, you need to precisely measure the voltage at the battery
terminals, under a known load. This can be done with a good digital
voltmeter, using just a headlight for a load, but it has to be done off
the bike using a simple test jig.
regards,
Joe
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>> A lesson I've re-learned a number of times on bikes and cars: Even
>> a little six-inch ground strap when the ends are corroded/oxydized
>> or even thinned due to use might have as much as a quarter-ohm
>> resistance. A 300 watt starter motor has a resistance of less than
>> half an ohm. In that case, a 12 V battery would lose a third of
>> its voltage, ie., 4 V on the ground strap, leaving only 8 V max for
>> the starter.
>
> Actually, it's a lot worse than that. Even small starter motors will
> draw a locked rotor current of 100 amps or more. That means the
> resistance of the starter windings is around .1 ohms and it's not
> unusual for larger two cylinder engines to have starters that have
> less than .04 ohms. Your 300 watt starter will draw more than 150 amps
> initially and have a resistance of less than .075 ohms. That's why we
> require starting batteries in the first place, they are specifically
> made to provide far higher short term current than deep cycle
> batteries.
> ...