- Hey, I'm Evan, Head of Engineering from RM Stator.
Today we're gonna show you how to test your stator.
Depending on your vehicle, motorcycle, ATV, side-by-side,
watercraft, doesn't really matter.
All these types of power sports engines use stators.
And you need to know how to test them.
If you have one long enough,
you're probably gonna have a problem with it.
You're gonna need to know if it's good or bad.
Watch some of our other videos about what stators are
and how they work, so you know about the different types
of coils on the stator.
I'm gonna show you how to test the different kinds of
source coil, the pick-up coil if it's included,
and the charging or lighting coils on the stator.
So with that said, let's get started.
Okay so we're gonna show you how to test the stator.
These stators are obviously out of the motor.
A lot of times you'll be testing with your stator
installed in the motor, and that's not a problem.
You generally don't need access to the stator itself.
Just to the connectors out at the end of it.
So, here's a good example of a charging stator.
This stator has a single coil,
just meant to charge a battery.
You can tell by the large gauge
and barrel-looking copper wire on it.
So there's two different tests we wanna do on stator coils.
What we're concerned with is to see that
the coils of the stator are in tact,
so they're still connected end-to-end.
And we wanna make sure, in most cases,
that the stator coils are not grounded.
And by grounded, I mean touching the metal core
of the stator, in which case,
there would be continuity to ground or to the frame,
and therefore, the battery negative terminal
in a charging system stator that would prevent it
from producing any current.
So, what you wanna do is look up the specs on your stator
so you know what you're trying to test.
For instance, I know this stator,
if I look up the specs for it,
should measure about 0.4 or 0.5 ohms.
And that's between the two leads from the stator.
So, here I have my multimeter connected to the two leads
from the stator, and I have my multimeter set
to the correct resistance range.
Now, quick note on that.
Once you look up your spec and you know what measurement
you should be getting if the stator was good,
you wanna set your meter to the resistance range,
which is the ohms setting.
You can see by the kinda little,
upside down looking horseshoe guy.
You wanna set it to the lowest resistance range
that is above what you're trying to measure.
So that way you get the most accuracy,
but you can also take a measurement
within the range that you're expecting.
So here I can see that I'm measuring 0.4 ohms,
which is perfect for this stator.
And then the other test I wanna do is
I wanna see if the coil is shorted.
So, this just tells us the the coil
is in tact from end-to-end.
It could still be touching the core somewhere,
which we wouldn't want.
To test that, I can leave one of my meter leads connected
to either leg of the stator, either terminal.
And I can connect my other one to the metal core
of the stator.
In this case, I should be measuring an open circuit.
Depending on your meter, it might show "OL"
for open loop, meaning there's no connection
between your two leads.
This meter shows a one with the decimal place far away,
saying it's not a valid number.
So, this shows us this has an open circuit to ground
which is perfect for this kind of stator.
So let's check out another type.
Okay, so here is what's called
a three-phase battery charging stator.
We know it's meant to charge your battery
because it's got large gauge copper-looking wire on it.
And it has three wires in it, and they're all yellow.
So that's pretty standard, that tells us
it's a three-phase stator, which means it has three coils
right around the stator.
What we wanna do is the same test we did before,
we wanna measure between each coil to know
that each coil is in tact from end to end.
And then we also wanna measure from each coil
or at least one of the coils to ground to the metal core
of the stator.
Which, if this was installed in a motor,
we could just measure to the frame or the motor mount bolt,
or the battery negative terminal.
Cause they would all be connected
through the mounting bolts.
So I looked up my specs for this stator,
I know it should be about 0.4, .5, .6, something like that,
depends on the multimeter.
So a quick note about checking charging stators like this,
with this large gauge wire, it has very low resistance.
And we have a spec that may say .5, .6.
What we're looking for is that the number is reasonable.
Which would be below one ohm.
And we also wanna see that we get the same measurement
between each coil, because each coil
should be the same length.
I always say with charging stators like this,
that use fairly large wire like this,
don't be so concerned exactly what the number is.
Like you can see on the meter here, we're measuring .4.
And that's totally fine, we may take this same measurement
with another brand multimeter and measure .6 or .7.
So we don't really need to be super concerned with that.
Most meters, especially fairly inexpensive meters
like this one, are not super accurate at very low resistance
below one ohm.
So we don't need to be super concerned about the number,
we just wanna be concerned that it's reasonable,
which is less than one ohm.
And that we get the same number
between each of the three pairs of wires.
So here's our first pair, we're measuring one of the coils,
and we're getting a reasonable number, .4.
So then I wanna swap one of my meter leads
to the next terminal and actually get the same thing.
So .5, that's fine, within a tenth of an ohm.
That's totally reasonable.
You can see the meter changed a little bit back to .4,
as it takes the measurement.
That's totally reasonable.
Then I wanna check the the third coil,
so I'm gonna move this up to here.
So now I've tested all three combinations,
which would measure between each of the three coils
of the stator, and I can see that I get the same thing.
Okay, so that's fine, that says that all three
of these coils are in tact from end to end,
and they're a reasonable number on our meter.
So that says that the coils are good,
what it doesn't tell us is if we have a short
to ground in the stator.
Since I know that all three of these coils are connected,
it doesn't matter which one I leave my meter on.
So I'll just leave that guy right there.
Then, I'm gonna connect the other end of my meter
to the metal core of my stator, and see what it says.
So here I get a one with a decimal place far away,
that says an open circuit.
There is infinite resistance
and there is no connection to ground,
so this stator is good.
So now let's take a look at a different type of stator.
Okay so here we have a three-phase battery charging stator
that also has some other stuff.
We can see that it has a pick-up coil attached,
which if you you've watched our other videos
about what these parts are,
we know that's for the ignition system
that provides our timing pulses for the ignition system.
And we can see that, if you look close,
there's a green and a blue wire coming out of that.
And we can see that green and blue wire
in that four-pin plug here.
Well, there's two other wires in this stator, as well,
a black and a white.
So, I'll tell you, you can't really see it,
but the black and the white is called
the "position sensor coil."
It's usually used on bikes or ATVs
with a big, single-cylinder motor.
And it's used for kick-back prevention.
So, it basically will be producing a voltage.
It's a very small coil wrapped under one of these.
It'll have very low resistance
and it will show, basically,
the polarity of the current coming from that coil.
So the CDI box can tell if the motor is trying to turn back
or if it's from kicking back, and it'll kill spark.
We'll show you how to test that, as well.
So first we're gonna test our battery charging coils
on the stator.
Again, we wanna know that they're all connected end to end.
And we know that there's three coils,
and they're all connected on these yellow wires.
And we wanna measure something like .5, .6,
between each pair.
So we're doing that now, we can see one pair's good.
I'm gonna test all the combinations of these.
Here's the next one.
I get .6, as well.
And I'll go to the last combination.
And I get .6, as well.
So that says each coil is good from end to end.
The other test I wanna do is to the metal core
or to ground, or the frame,
and see that I have an open circuit.
And I do. Okay, so that's good.
So now, let's test the position sensor.
So that'd be the black and the white wires here.
Now, that's gonna be a very small coil
of the same size wire, so it's gonna have
very low resistance, as well, below one ohm.
So I'm gonna leave my multimeter set to the same range,
the lowest range I have.
And I'm measuring a low resistance, about .4.
So that looks good.
I can also check it to ground,
and make sure that it's not shorted to ground.
And it's not, so that says that coils good.
And then we wanna test our pick-up coil.
So I looked up the specs for this stator.
I know that the pick-up coil should be 220 ohms.
So I'm going to connect my meter to it,
the blue and the green wire in this plug.
So you'll see here, I'm just showing an open circuit.
Well, why's that?
This is a brand new pick-up coil, it shouldn't be bad.
Well it's because I have my meter set
on the wrong resistance range.
I'm trying to measure 220 and my meter's only set
to read up to 200.
So I need to move my meter up one click,
to the 2K setting.
So now the meter's expecting a measurement
anywhere between zero and 2,000.
And now we'll see if the meter
is showing the correct reading, 221.
And you'll see the decimal point there,
because I'm on the 2,000 setting.
So if I move that over, I get 221,
which is perfect for a 220 ohm coil.
So, I can also, this doesn't happen often,
but I could check it to ground as well,
just to make sure it's an open circuit, and it is.
Okay good, so that tells me that all the coils
are good on this stator that has multiple parts.
Alright, here's a stator that's common.
This type of stator's common to dirt bikes and ATVs.
You can tell that it has some battery charging
or lighting coils here with the larger copper wire.
And then, we can see that it has some other coils
that look different, and they're cloth-covered.
So those are a source coil to power an ignition system
directly from the stator,
so that's a different type of coil we'll have to measure.
It also has a pick-up coil for a timing signal.
So, first I'm measuring the source coils.
That's between this, on this particular stator,
this black with the red stripe and this brown wire.
And one side of the source coil's grounded,
which is the brown wire,
and the other side is this black and red wire.
So I looked up the specs, I know it should be 118 ohms,
which is exactly what I'm seeing.
I have my meter set on the 200 range,
so I can measure that number.
And since I know one side's grounded,
I can also go ahead and connect one side of my meter
to the core of the stator,
and I should get the same measurement, which I do.
So again, always look up the specs on your stator,
so you know what you're trying to test,
what wire colors you're testing between,
and what the measurement should be.
So you know how to set your meter correctly,
and you know if you're getting the right measurement.
So the other coil, or the next coil I'm gonna test,
is this lighting and battery coil,
which I know is between these white and green wires.
So I'm gonna go ahead and connect my meter to those.
And that, from the specs, should be a low resistance,
about 0.6, which it is.
Okay.
And I'm gonna check it to ground, it should not be grounded.
So I have one lead connected to the metal core
and I see an open circuit, that's good.
And then, I wanna test the pulsar coil.
So I'm gonna connect to its wires.
Okay, so I see that my measurement went away
but that's not likely for a brand new coil.
Well, that's cause I'm trying to measure over 200 ohms
and I had the meter set to 200 ohms.
I'm gonna bump it up a range to 2K,
and this should measure about 250 ohms,
and I'm measuring 247.
So that says the pick-up coil is good.
To be safe, I know it should not be grounded,
I can go ahead and check to the metal core of this stator.
And I see an open circuit.
Or I could check the metal bracket of the pick-up coil,
and I see that's open.
So that all tests good.
Alright, let's look at one more.
Alright, here's a type of stator with bar coils,
so it kinda looks different, but we test it the same way.
We need to test each of these coils separately.
So, we have a source coil here, and it's used
for the ignition system and power.
We have two coils here with larger wire
that are used for the lighting
or the battery charging system.
And then we have a pick-up coil here,
that provides timing for the ignition system.
So, we need to test them all separately.
On this stator, the black wire with the white stripe
is grounded, so I have it here also tied to the ground,
the metal core of the stator.
And then I'm gonna measure each of the three other wires,
which are the different functions.
So, I know what they are and what they should be
from looking at the specs online,
which you should always check first.
So first I'm gonna check the alternator,
the lighting or charging coils, which are these guys.
And they should be low, about .6 ohms,
.7, that's fine.
And that was the yellow wire so I'm measuring
from there to ground, or to the black with white stripe.
So that looks good.
And then I wanna measure the pick-up coil.
So I'm gonna switch the blue wire here,
which is the pick-up coil.
And my meter shows an overload, so I need to go,
or an open loop, I need to go up one step to read it.
And it should be about 240, which it is,
so that tests good.
And then my other test is the source coil,
which should be the third wire.
And that shows about 380, which is what the spec is,
so that shows that the source coil is good.
So, as always, look up the specs online on our website.
Make sure you know what you're measuring
and what it should be.
Make sure you set your meter accordingly
to the correct resistance range.
And sometimes, some of you have auto-ranging meters
which will set the range correctly on its own.
So that makes it a little easier.
But as long as you followed those steps,
you know what you're measuring and what it should be,
you can measure it accurately and you can do the same thing
whether it's in the bike or out on the bench.
So here we're gonna look at how to actually test the stator
on the bike.
You definitely wanna do the resistance test first,
but then we can also do a voltage test
with the motor running, so we can see if the coil's
producing what it should be.
So, the key to this, is we need to measure the voltage
between all three coils on the stator.
We're using a three-phase stator here.
If you're using a two-wire single phase stator,
you would just check between the two wires.
So here with the three-wire stator,
once we have the motor running, we wanna check the voltage
at idle RPM, which we'll say is about a thousand RPM.
And we wanna measure the AC voltage
between each pair of wires.
So, what we're gonna do is plug our meter in.
I have our meter set to AC voltage, and to the 200 setting,
which is our lowest range.
We're trying to measure between 10 and 60 volts AC,
so the 200 setting is fine.
And I have the two leads of the meter connected
to two of the stator wires.
We're gonna set this on a test bench
spinning to about a thousand RPM,
and we're gonna measure the voltage
and see if it's reasonable.
For this type of stator, we should be seeing
somewhere around 10 to 15 volts AC at idle.
And then we're gonna check all three coils
and see if they're even, we get the same measurement.
To do that, we're just gonna change one wire at a time here,
at the stator plug, so we check all three pairs.
So go ahead and spin the fly wheel up here
to about a thousand RPM.
Let's see what our voltage is on the first coil.
Okay, perfect.
So we're measuring about 10 volts AC on our first coil.
So then I'm gonna take our meter
and change it to the next pair.
And I measure 10.3 again, so that coil's even.
And we're gonna check the last pair.
And 10.2.
So we've checked all three pairs,
and we're getting good output for idle RPM
and they all match, so that's okay,
the coils are all in tact and they're all still even.
The other thing we can also check is,
we know all three of these coils are connected,
so we can check to any of them to a ground
just to make sure that we don't have a path to ground
from our stator coil.
So I'm gonna unplug one of these and touch it
to the metal here, which would be the same thing
as our motor case or our frame on the motorcycle.
And we show zero volts, so that's good.
That says the stator's not shorting.
And again, this is done with the stator unplugged
from the regulator, so there's no load on it.
I'll plug this back in, we'll see our voltage measurement.
And then, totally depends on your stator,
and how it's wound as far as what voltage you'll get
at higher RPM.
This is pretty standard for a battery charging stator.
This stator is a really high-power, high-current stator
for a Polaris RZR, so it doesn't produce super high voltage.
We're gonna rev the fly wheel up
to four or five thousand RPM or so,
and we're gonna see about 30 volts on this,
which I know is correct for this type of stator.
On a lot of smaller charging stators,
you'll probably see upwards of 60 plus volts AC.
Okay, so where is our high RPM measurement,
we're seeing about 30 volts on one pair,
and we're gonna check all three of them.
Let's see if I can keep the meter from falling over.
Here's our second pair, you're seeing 33 volts, as well.
And I'll check our third coil on the stator,
and we're still measuring 33 volts.
I can check the ground, as well, just to be sure.
And I get no voltage.
Okay, perfect, so go ahead and turn it off.
So that's how you're gonna test a stator on the bike.
Again, you're gonna set your multimeter
to the AC voltage setting.
And you wanna check it at idle and at about 5000 RPMs.
So you're checking it at low output and at high output.
And see, if the numbers are reasonable,
then you know you're getting good output from your stator,
and you can assume that it's working well.
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