Start the bike, check the
voltage, blip the throttle quite hard, if the voltage doesn't rise
from around 12.5/13 volts to about 14/15 volts you've got a charging
problem some- where. If you rev the bike out and the voltage doesn't
hit a peak at around 15 and then drop, but instead carries on rising
to 17, or even 20 volts then you've got a duff regulator. The charging
problem could be down to a knackered alternator, but with a GS it's
more likely to be the reg/rec, certainly a knackered alternator
will probably have taken the reg/rec with it. So rip the old unit
out and fit a better version.
(Webmaster's
Note - The most common cause of reg/rect demise is that the GS is
run low on oil on a long run. The alternator gets hot and chucks
out a huge voltage which usually destroys all in its path - on my
850 it took out everything including the electronic ignition and
the battery...)
As I said, most bike reg/rec
units are essentially much the same, so you can interchange them.
The only real difference (apart from being a positive earth type
rather than negative earth as is normal these days) is the predetermined
voltage at which the regulator function will switch excess voltage
away, more on this later.
Because of their reliability,
availability, and most importantly, their cheapness, most people
plump for second hand Superdream units. 250 or 400 will do, even
the tightest breaker shouldn't charge you much over a tenner for
one. Buying secondhand electrical parts can be a bit risky, just
by looking at them you can't tell a good part from a bad one (unless
it's still smoking).
You might have a good
breaker near you that'll exchange bits found to be dud, (c'mon,
be fair, it might happen), personally I'd be happier testing the
unit in the shop before I part with my dosh.
Now you can't really test
the regulator function without the unit actually being fitted onto
a bike, but you can check the rectifier side of it quite easily.
Get your Superdream unit, set your multimeter to the resistance
scale and connect the positive probe to the green lead, then connect
the negative probe to each of the yellow leads in turn.
Then repeat all this with
the positive lead instead connected to the red/white lead. The resistance
for each pair of connections should not be more than about 30-40
ohms.
Now reverse the meter leads,
in other words connect the negative meter probe to the green lead,
then to the red/white lead, and test each of the three yellow leads
for each connection. The resistance this time should be at least
2000 ohms, (it may say 2K, ie thousand, Ohms), don't worry, it's
a lot easier actually to do this than it is to read about it. Or
to write about it come to that.
If all that checks out,
or if you give up in a blind panic half way through, give the bloke
your money and worry about it all on the way home.
Or you might already have
chosen the famous 'Plan B', having assumed that your original rectifier/regulator
has shuffled off this mortal coil, you decide to replace it with
a Superdream unit and can't be arsed, or can't, check it out at
the breakers so you buy it and fit it regardless.
It's a great plan, simple
and foolproof, unless it goes wrong. In which case you just do it
again and again and again until it works. Just like Honda with its'
V Fours.
Here's how you hook in
your new secondhand unit, the Superdream unit has three yellow leads
connected to a plastic block connector, one black lead, one green
lead, and one red/white lead connected to another block connector.
You can either do things
poshly and get hold of suitable other halves to these block connectors
or just chop 'em off and use bullet/spade/chop-block/whatever connectors
you prefer. The important thing is to make the right connections.
