Advice on GS500 with electrical problem please (long story)

I replaced the battery in my wife's GS500 about 4 months ago, as it was
becoming difficult to start, only cranking over 2 or 3 times before the
battery was too low. As the battery was around 5 years old, this seemed
to be the most likely cause.

The bike is only ridden rarely, maybe once every 4 to 6 weeks, and after
fitting the new battery we found that each time she went to use the
bike, the battery was dead, and we would have to jump start the bike.

Our assumption is that the aftermarket heated-grip controller, which is
meant to turn off the grips when the engine is stopped, may have been
continuing to draw current, and flatten the battery.

I have recently bought and started to use a battery charger, to try to
keep the battery topped-up when the bike is idle. This weekend when we
went to start the bike, it would not turn over, and the dash and
headlights were very dim. The battery charger however was indicating
that the battery was charged, and a voltmeter showed around 12.4 volts.

I jump started the bike from the car, then detached the jumper leads.
At idle the voltage across the bike battery was just over 12 volts.
When I revved the engine it fell to less than 9 volts.

I think we may have 2 problems here.
1. A stuffed battery because we let it go completely flat when it was
first fitted, and
2. Something wrong with the alternator/regulator on the bike, so that it
is not charging the battery, as I expect the voltage on the battery
should rise when the bike is revved from idle, not fall.

Any thoughts or suggestions please of what I could try, before I resort
to taking it to the local bike shop.

David

 

What year GS500? Does it have brushes in the alternator?
If not then there's not a lot you can do except check all connections;
especially the battery, engine and regulator earths... and then start
replacing bits. (Regulator/rectifier first)
Good luck,
Clem

 

Assuming it's a normal alternator I would check the rectifier pack or
alternator has not dropped a phase , usually they drop a diode or two so
checking in and out with a meter will at least indicate what's going on
, you really need a manual or a savy friend .

 

You're spot on with the suspicion of stuffed charging system. Voltmeter
should read between 12.5 and say 14 volts after 3k or so RPM however a dead
battery can cause all sorts of dodgy readings when trying to trace a
charging system fault.

Remove or disconnect the battery then connect another serviceable battery,
perhaps a car battery via jumper leads, and perform the voltmeter test
again. It's likely that the voltage will remain at 12 volts indicating no
charge. If so then you've got to test AC volts from the alternator then DC
volts from the Reg/Rec If you're not clued up it's probably a job for an
auto electrician familiar with bikes. If by chance the voltmeter test
reads OK then replace the battery with a gel type. Replace it with a gel
type in any case. They can handle extended periods of inactivity much
better than the wet type. And buy a decent trickle charger.

Last test should be with a charged battery and an ampmeter connecter between
the battery negitive and earth to test for any current flow when the bike is
switched off.

It's also good practice to disconnect the negitive if the bike isn't being
used for extended periods however connecting a trickle charger negates the
need for this. Just good practice.

Capt. A. L.

 

Notwithstanding the other sensible advice already offered, and
acknowledging that I know squat about electrics, nevertheless: the
battery discharging despite the trickle charger implies either a stuffed
battery (preferably) or a leak of some sort - you can test this by
pulling the battery out and trickle charging it; the voltage drop when
the revs are raised MAY indicate a stuffed reg/rec, but it may be an
artefact of the voltmeter and the surface voltage; and there is no
better way to bring motorcycle electrical problems to the fore than to
fit heated grips, because they are almost never fitted via a relay
through the ignition switch, but rather are wired direct = prime source
of earth leakage.

You didn't say how old the bike was. If you can afford it, replace the
reg/rec (not very expensive, about the price of a shop fitted battery),
replace the battery (preferably not with something made in the PRC) and
throw away the heated grips (on a bike that gets used once in 4 - 6
weeks, heated grips are silly).

You could also ride it a little more often. Internal combustion motors
are not designed to be idle for weeks. When you park your daily drive in
the garage overnight quite a lot of oil remains coating critical parts
the next morning. 6 weeks later there's nothing there, and you can add
10000km worth of wear in the first few seconds after starting the motor.

 

That is pretty cluey 4 sum 1 that reckons they no nothing bout leccy,
respect

 

Thanks to all for the advice.

I tested the bike with it's battery removed, and with jumper-leads
across to another bike, and the voltage on that battery showed the
expected behaviour (ie >13.5 vols at idle, and >14 volts with a few revs).

So I have replaced the battery, and the bike is now on a trickle charger
when not in use.

The heated-grips are currently disconnected, until I install a relay to
ensure they are only drawing current when the ignition is on.

Thanks again for the advice.
David