Motorcycle Forum / General / Yamaha / May 2007

Jones <wp.jonesspam@btinternespamt.com> haute in die Tasten:

If there is no charging while the engine is running, either the
alternator or the regulator is broken. An experienced motorbike
repair shop should be able within minutes to find out which component
does not work. You should not hesitate to find out the problem,
because it may result in a deep discharged battery. If the regulator
is broke, it can be replaced quite easily, because usually it is
bolted to the frame. The regulator has about the size of a pack of
cigarettes and has a metal case with cooling fins. If the alternator
should be broke, things get worse, because you have to open the
engine.

Frank

It would be nice if you would tell us what year your bike is with the very
first post, so we don't have to guess.

Your problem might be as simple as dirty battery cables, so the first thing
to do is clean the cables
and the battery posts with a wire brush until they are bright and shiny.

Most Japanese motorcycles have a permanent magnet alternator with a shunt
type rectifier regulator.

"Shunt" means that the regulator automatically shorts out one or two stator
leads to ground and burns up excess current by converting it to heat whenever
the voltage reaches about 14.5 to 15.0 volts DC.

This doesn't hurt the stator or the regulator, the regulator is designed to
get hot, that's why it's built inside a finned heat sink.

If you want to see pictures of what these parts look like, go to www.bike,
bandit.com.

Click on OEM Parts > Yamaha > whatever year your bike is > XV1100 and you
will see a list of "schematic" parts diagrams. Look at GENERATOR and ELECTRIC
schematics.

You don't need to remove the generator cover unless the stator fails the ohm
meter or open circuit voltage tests or you're right away curious about
whether the rotor is turning...

The permanent magnet rotor has to turn when the engine is running, and if
your rotor *isn't* turning when the engine is running, it's chewing up the
end of the crankshaft.

Major bummer. Been there, done that, hated it.

The rotor induces a voltage in the stator, which has three coils arranged in
a "wye". If you follow the cable coming from the alternator stator, you'll
find that it ends in a plastic connector with three square pins.

Examine this connector carefully to see if it, or the connector it is mated
to has gotten hot and melted.

That is a very common problem with Japanese motorcycles that have permanent
magnet alternators.

If the connector is melted or burned looking, you can either hunt down a
replacement connector, or you can just cut the connectors off the wires,
strip them, twist them together and solder them together.

The three AC output wires from the stator might all be white or they might
all be yellow, or if the engineer was picky, they might all be white with red,
blue and yellow tracer stripes. It doesn't matter.

It doesn't matter which one of the three stator AC leads goes to each AC lead
of the rectifier regulator, it will work just fine. The RR unit doesn't care
about phase rotation.

Many riders who have melted the connectors on their bikes have soldered the
wires together as I described and slid plastic heat shrink insulation over
their "Western Union splices"

If the connector is not melted, burned, or corroded, that's one bullet you've
dodged.

Now you can use an ohm meter to check out the stator. You can get cheap
pocket ohm meters from Harbor Freight for as little as $7.00. When the
internal battery goes dead, you can just throw the meter away.

On the Rx1 scale, you should read something like 0.5 to 1.5 ohms from any of
the three stator wires. Don't worry about the other wires that come from the
pulser coil, you want the three wires that put out voltage from the stator
itself.

The stator is wound in a "wye" configuration. Imagine each coil as one of the
legs of a Mercedes Benz emblem, meeting in the center. If you put the ohm
meter probe on any of the three leads, you should read the same very low
resistance to each of the other leads because they are all connected in the
center.

But they are NOT connected to the metal case, at least not intentionally.

If one lead reads different from the other two leads, the stator is
internally shorted and you need a new one. Electrosport makes aftermarket
stators that are a lot cheaper than Yamaha stators.

If the three leads all check out the same to each other, switch your ohm
meter to the rX1000 scale, and check from each lead to a bare spot on the
motorcycle's frame. The resistance should be more than 500,000 ohms, maybe as
high as a million ohms.

If you read less than 500,000 ohms, the stator is shorted to the case and
needs to be replaced.

The next step is to check out the six power diodes in the rectifier regulator.
You need to have the RR disconnected from the battery and from the stator to
do this test.

Put the ohm meter on rX1 and check from each of the three AC power pins that
mate with the stator's
AC output pins.

Like I said before, it doesn't matter what AC pin you get on, you're looking
for identical readings to find any reading that's different. Different
readings indicate problems.

Put the positive lead of the ohm meter on each of the three AC inputs in turn
and check for continuity to the DC output lead coming from the RR. The DC
power output will probably be a red wire or it may be white with a red tracer.
If you don't get any reading on any of the pins to the DC power output,
reverse the leads and check again.

You should read something like 15 ohms, but I can't tell you for sure because
I don't know what kind of ohm meter you might be using.. Analog ohm meters
(the kind with indicating needles) with less internal resistance will cause
the diodes to read differently than ohm meters that are designed to check
diodes.

Anyway, just like the stator test. all three AC inputs to the RR should have
the same reading to the DC power output wire.

Then, you can reverse your leads again, and check from each of the three AC
input wires to the negative lead coming from the RR. If there is no black
wire (or white wire with a black tracer) coming from the RR unit, check from
the three AC power wires to the RR's metal case.

(Also, if there is no negative DC output lead, the RR unit depends on being
bolted to a nice clean spot
on the chassis to get a DC ground. This makes problems, because the RR is
also better off having white heat sink compound applied to the backside to
help it get rid of excess heat.)

Again, you should get three identical readings. If you wind up with any diode
that doesn't have the same reading, the RR is toasted and you need a new one.

If any diode is burned out, it cuts the RR output current in half, and the
battery will slowly go dead as you ride. Slowly discharging without being
recharged is the worst thing that can happen to a lead acid battery. I
sulfates and cannot take a charge afterwards.

Again, Electrosport makes aftermarket regulators that are cheaper than Yamaha
regulators.

If your RR checks out OK, you can do the open circuit voltage test on the
stator. Don't connect the stator plug to the RR plug. Start the engine and
warm it up and then put your voltmeter on the 150 volt scale and check from
each of the three AC output wires to the other two. With the engine turning
around 3000 or 4000 RPM, you should see something like 90 to 120 volts AC
coming from the stator.

(Do not attempt to ride the motorcycle with the stator disconnected. You can
damage the insulation on the stator windings, it's just enamel or epoxy
coating on the copper wires, not cloth or plastic insulation.)

Shut the engine off and hook up the stator to the RR unit. Put your voltmeter
on the 15 volt DC scale.

Now you can check the voltage regulating function of the RR. You need to
charge your battery fully with a charger before doing this test.

With the RR hooked up to the stator, measure the voltage at the battery
positive terminal with the engine not running. You should see around 12 to 12.
8 volts with the engine off.

Start the engine and watch to see what happens when you increase the RPM to
about 3000 or 4000
RPM. You see see the voltage rise up to about 14.5 volts or even 15.0 volts
DC Then the voltage will drop back to 12 to 12.8 volts.

When you roll off the throttle and then increase the RPM to 3000 to 4000 RPM
again, you should see the same rise and fall in voltage that proves the
voltage regulator circuit is working OK.

Good luck troubleshooting.