Topic: Is a fast idle bad??

[TwoTired]

With that being said I tested the resistance across the copper windings of the rotor and got ~ 5.5 ohms. 

That's a reasonable rotor resistance for a field coil.  I don't know the exact spec for this bike, though.  Still, it ought make enough magnetic field in which the the stator can produce power.

i then unplug the stator from the R/R it had 5 wires - 3 yellow, 1 black (hot), 1 white (neutral).  i tested the resistance across the black and white and got off scale reading. 

The black and White wires function is to deliver battery voltage to the alternator (to make an electromagnetic field).  I can't determine if the plug you checked is wired to the alt or to the R/R.  If it's the plug to the alt. it should read pretty close to the 5.5Ω you measured at the rotor slip rings.  If it's the plug wire from the R/R, and you R/R is a solid state device.  You may need a meter that supplies enough voltage to make a diode or transistor junction conduct.  If the voltage provided by the meter is too low, it may well read infinity as the regulator output will not pass any current for the the meter to measure.  Digital meters usually have a diode symbol on the knob setting scale for testing active devices.  The symbol looks something like this  -|>- .  However, I don't know the internal design of your regulator.  So, any reading made to the output of that device is speculative as to correctness.
You'll probably have to measure voltage on the Black and white wires with then properly connected and the key switch on.  For any battery reading below 12.6V the black and white wires should have very close to whatever the battery reads.

Across any of the three yellow wires was about 1.3 or so.

Probably nothing to worry about here.  Technically, this reading should be lower.  But, you need a meter that is accurate for lo ohms, and you need to subtract the meter's own test lead resistance from the meter's reading.

The last test I grounded the common probe to the engine block and used the red probe and a spot tester.

The engine block and the battery NEG terminal should be the same electrical potential.  You should gain confidence that this connection has integrity.  In fact, you should gain confidence that any green wires have good electrical conductivity to the battery NEG terminal, too.

Cheers,

[jonnycbgood]

The rotor resistance is supposed to be between 4 and 5. so my rotor is good   

When I tested the black and white wires I had the alternator cover off so the brushes were not in contact with the rotor, which is probably why I got infinite resistance.  I will redo that test tomorrow.  I was checking the plug from the alternator not the R/R.

so my yellow wires are good which means that stator is good.   

I will verify the black and white wires which will tell me if the brushes are good?

Then the next thing is to test the R/R...There is a test where you bypass the regulator to see you can charge your battery that way.  I believe I will try that test as well.

[TwoTired]

so my yellow wires are good which means that stator is good.   

I've learned through the years that until it works to satisfaction, nothing is guaranteed good.  It is, currently beyond immediate suspicion.

I will verify the black and white wires which will tell me if the brushes are good?

You might want to clean/polish the slip rings, if you have convenient access.  And, just to eliminate unknowns test the rotor circuit path at the R/R connection point is well worth the time.

Then the next thing is to test the R/R...There is a test where you bypass the regulator to see you can charge your battery that way.  I believe I will try that test as well.

Check first if either of the Black or White wires have a connection to frame ground.  Most of the SOHC4s do.   I'm not sure the DOHC does, as I don't have wire diagram for it.  I also don't now which of the R/R outputs provide the positive path to the rotor and which one is the return path.  Applying battery voltage to either output may destroy the R/R, as it is expected to deliver not receive power.   However, when the rotor is provided full battery potential across the Black and White wires, it makes the strongest magnetic field, so the alternator can put out full power.  A 12V voltage applied to a 5.5Ω resistance draws 2.18 Amps.

I would also do a diode resistance check on the six diodes in the R/R.  These converts AC from the Alt, to DC that the battery can use.

Cheers,

[jonnycbgood]

Okay I did the diode test on the R/R...in the normal direction I got a resistance of ~2.5 and the spec is 5 - 40...in the reverse direction I got infinite.  This is using the new calibrated meter.

I retested the black and white wires coming from the alternator and got 8.5ohms.  Also the brushes are not even close to the scribe service limit so I believe them to be good.  The black and white do not have a connection to ground.  The black is the supply and the white is the return.

The main fuse is a 30 amp with the key on and leads placed across this fuse I got -7.5 amps? this number didnt change when I started the bike.

I am thinking that this means the R/R is bad due to the diode test and the rotor, brushes and wires checking good.  Is this a safe assumption?

"You might want to clean/polish the slip rings, if you have convenient access.  And, just to eliminate unknowns test the rotor circuit path at the R/R connection point is well worth the time."

Are the slip rings on the rotor or stator?  what would I use to polish them with?

[TwoTired]

Okay I did the diode test on the R/R...in the normal direction I got a resistance of ~2.5 and the spec is 5 - 40...in the reverse direction I got infinite.  This is using the new calibrated meter.

It is important the diodes conduct in one direction only.  Your test seems to verify that.  Did you test the rectifier as one unit or did you check the six individual diodes?

I am thinking that this means the R/R is bad due to the diode test and the rotor, brushes and wires checking good.  Is this a safe assumption?

Not yet.  A low resistance in the forward conduction direction is a good thing.

"You might want to clean/polish the slip rings, if you have convenient access.  And, just to eliminate unknowns test the rotor circuit path at the R/R connection point is well worth the time."

Are the slip rings on the rotor or stator?  what would I use to polish them with?

Slip rings are on the rotor.  Isn't that where you measured them before?  Where the brushes make contact?

They can form a glaze that the brushes may have a hard time penetrating.  Cleaning the rings with 400 grit paper, should shine it up well enough.  If you want to check for spinach in your teeth, then use Semichrome polish.
After you do that, the 8.5 ohms you measured before should be lower.

Btw, remember I told you a 5.5 Ω rotor would take 2.18 Amps?  If the R/R sees 8.5 ohms, that limits the current to 1.4 amps; meaning the magnetic field strength for the Alternator will be about 2/3 what it should be, making the alt output weak.

Cheers,

[jonnycbgood]

I just have to say this...you are a genuis.  thank you so much for helping me with this problem. 

I will polish the rings today and see if that helps and then report back.

[jonnycbgood]

It works!!!  I got some contact cleaner and cleaned allthe connections and polished the slip rings.  the resxistance btwn the black and white then matched the rotor resistance exactly.  I also replaced the 30 amp main fuse and now the bike charges 14.6 volts at 3K rpm.

thanks again for all your help.

[tonycb650]

Just curious, did this fix your original problem of a fast idle?

[jonnycbgood]

It has definitely improved I had it idling at 1500 rpm but it wasnt consistent.  It would bounce between 1k - 2k but mainly hang out at 1500.