Topic: I think I found the problem! or Help Two Tired!

[vhenle]

I tested my field coil tonight and it read 8.3 ohms ( The white and green wire at the bullett connectors by the Alt), is my field coil bad?
 I also had something strange happen that might help someone later.  I was riding the other day and suddenly the bike starts missing like crazy. I pulled over and messed with it for a bit, no better.  I get it home and go through all the normal things, spark ,fuel ect..
I find the #3&4 cyl's are not firing (cold pipes). Replaced plugs (had them laying around) no help. I got this strange idea to charge the battery and try it again, ran like a dream! I just installed the Dyna S ign. a few weeks ago and I guess the lack of voltage caused the misfiring?

Chad

[TwoTired]

According to the shop manual, your field coil should be 7.2 ohms.  When measuring with a dmm, however, you must subtract out the meter's lead resistance.  Put the meter on the lowest resistance scale, place the probe tips together, and note the reading.   This is your test lead resistance and this number must be subtracted from your reading on the field coil.

If it is within a couple of tenths of the 7.2 ohm spec., it's probably okay.

Cheers,

[vhenle]

I did what you said with the meter and it showed 0.3 when leads where held together. So that would make my reading 8.0 ohms?
Thanks for your quick reply!
Chad

[bryanj]

It ought to be ok at that reading and to be honest the two generator coils rarely go west any way. You need to do a full charging cjheck as in the manual

[TwoTired]

8.0 ohms is about a 10% variance in the rated spec.  I'd like to see within 5%.  But, your resistance reading alone is not enough evidence to condemn the field coil.

Bike system voltage checks are in order.  With the battery fully charged, measure:
A- Voltage across battery terminals (ignition off)
B- Voltage across battery terminal (ignition on)
C- Voltage across white and green wires at Vreg.
D- Voltage across black and green wires at Vreg.
E- Voltage across battery terminals (ignition on)   (Because of battery voltage drop with use, do these tests within a short time span)

Kick start bike.  Measure voltage at:
F1- Idle
F2- 2000 RPM
F3- 3000 RPM
F4- 4000 RPM
F5- 5000 RPM.

Pull head light fuse (or light switch off) and repeat F tests for readings G1-5.

Cheers,

[vhenle]

I will check that out and get back to you, thanks!

Chad

[vhenle]

Here it is!
A) 12.64
B) 12.30
C) 8.4
D) 11.42
E) 12.22
                   W/ Headlight fuse        W/o
F1)                       12.34                12.32
F2)                       12.64                12.66
F3)                       12.80                12.78
F4)                       12.96                12.98
F5)                       13.09                13.51

Let me know what's next!
Chad

[TwoTired]

Do I assume correctly you have the stock Vreg?

If so, its not happy.  With the battery voltage being as low as it is, it should pass the voltage on its black wire terminal to the white wire terminal with very little lost.  You are showing a 3 volts loss, which means the contacts inside are likely buggared (technical term).

Your options are to replace it or open it up and clean the contacts.    Depending on how aggressive you clean and how much wear and carbon is built up on the contacts while in the up position, you may also have to readjust it, too.  But, don't do that untill it is passing full voltage between black and white terminals.  If you clean, use an abrasive that will not leave bits of itself in teh point contact metal.  A points or relay contact file is good.  A polish after with crocus cloth, and then burnish with the back side of the cloth works well.

The other concern is that you are losing almost a volt between battery and Vreg connections.  (I've seen worse, though.)  This loss can be in the battery terminal to solenoid to ignition switch to fuse clips or any other connection between battery a Vreg.  Check the path on the schematic.   The peak output strength of the alternator depends on the field coil getting as much of the battery voltage potential as it can get.
Don't ignore the ground connection between battery and green wire at the Vreg either.  Voltage can be lost there as well.  Battery to engine, engine to frame, and frame to green wire connections, can all get corroded and lose electrical integrity, just as easily as the positive power routing.

You might ask, is .5 or .75  Volts really all that much?
Well, it is indicative of generally resistive connections that waste power at each connection as heat throught the bike.  You've got over a hundred connections in the bike.  If we allow each one to waste 1/2 watt, that's 50 watts dumped into the atmosphere as heat.  The 750 alternator puts out 210 watts peak and about 40 watts at idle (with full voltage on the field coil).  With lighting, the bike always consumes about 120-130 watts.  Add the connector waste in and the bike consumes about 170-180 watts.  The battery is only recharged when the alternator puts out more than the bike consumes or wastes.  How much of your alternator power do you wish to throw away?

Your running voltages are certainly on the low side.  But, it looks like the alternator is trying do what it can.   There is a possibility that there is a  rectifier diode open, which could also make a low output.  But, lets scrutinize that after we get the field voltage up where it should be.

Cheers,

[vhenle]

When I first started with this issue I replaced both the V Reg. and the Rectifer. Mine where old and I thought it wouldn't hurt? It is actually charging a little bit better since I replaced them. I bought the new ones from Oregon Motorcycle Parts the V reg looks to be solid state, its alot smaller than the original.
 I will look at my grounds and the other connections you mentioned and see where that goes. Thanks again for your help, from what I've seen on the forum you are the electrical guru.

Chad

[TwoTired]

Well, I don't know what the internal circuitry of your electronic reg/rect. is.  It should sense the black wire and put a voltage on the white wire according to battery strength.  But, I do not know the design parameters of that unit.  A three volt drop suggests it is limiting alternator output even though the battery isn't peak charged.

If you are still having issues with charging your battery, then you should contact Oregon Motorcycle Parts for guidelines on how that unit should perform.

I've not used one of those units.  And, I guess it is a possibility that it limits the rectifier output to prevent overcharging the battery.  If I had known you had a modified charging system, I would have added test E2 to the list, a measurement of Red/Wht to Green.

It may still turn out that cleaning the connections and restoring all the voltages to the correct levels throughout the bike will correct any problems you feel you have.

Which makes me ask.  What is the problem you are trying to solve?  Is your battery going down below 10 Volts?

Cheers,

[vhenle]

Originally I had no charging, even when the bike was over 3000k. The new battery fell to 11.30 and I experienced the cyl's not firing. After charging it back up to 12.75 the bike ran fine.  The old battery was bad, it wouldn't crank the bike over ( and failed load test). The new batt is doing a great job of that!
I will try cleaning the connections and I will contact OMP about the vreg. I will also do the E2 test, what reading should I get for that?  Can I bypass the reg to see if it charges?

Chad

[TwoTired]

The Red/Wht to Green measurement at the rectifier is the voltage being supplied to bike and battery.  In the ideal world, with soild, short connections, this would also be the battery terminal voltage.  In the real world, this should be a slightly higher voltage than the battery if the battery is being charged.  Since I don't know what specificly is inside the OMP box, I was qustioning if the box was sensing the Red/Wht wire to make it's regulating decisions rather than the Black wire.

To test the alternator for full output, disconnect the white wire from the Reg/Rect., and jumper the white field coil connection directly to battery positive terminal.   Don't put battery power on OMP's white output terminal or you risk blowing it up.

Anyway, assuming the OMP does NOT regulate the rectified output from the alternator, the battery voltage should achieve a higher voltage state when the alternator receives the full batt voltage on it's field coil and the engine is reved up.

Note that the battery voltage will climb slowly during charge and you must note trend info as well as instantaneous V levels.  Don't let the battery voltage exceed 14.5 for very long.  That can stress the battery.  Further, if you do get to 14.5 v, the alternator has proven itself fully capable.

11.3 volts should be plenty to fire the coils, providing that full voltage is getting all the way to the coil terminals.  I don't know the Dyna trigger low voltage limits.

Cheers,

[vhenle]

Well I went out tonight to look at the connections on my bike. Everyone always says start at the headlight, and what a mess! I have never had running lights, because they are not hooked up! I have included a pic where you see the botch job some PO did on my headlight wiring:( Can this be one of my issues with the voltage drop?

Chad

[jdamman]

Scotch locks!!!!!! Danger Will Robinson, danger!!     First Joel, second opinion: when thou seeith scotch locketh, stop all other electrical trouble shooting and replace with better connectors.  Yes, they are great and fast, however unreliable and suseptable to corrosion (please ignore spelling, engineering student, numbers only, thanks)  Do it once and do it right, otherwise you'll most likely be chasing bad connections from previous fast'n'nastys.
Later

[TwoTired]

The splices on the white and blue headlight wires look okay to me.  Usually are soldered under the heat shrink.  If so, they will be very stiff at the junction and difficult to bend there.

Those wire tap things are not my favorite.  They pierce the insulation and mash on the internal wires, but are not gas tight.  They corrode over time.  I assume those black wires outside the shell connect to the light blue and orange turn signal wires.  The run lights would be LB/Wht and Org/Wht.

The picture doesn't show any turn signal or run light connection.

Connector oxidation is not severe.  But, the socket terminals should look like bright shiny brass, at least where they make contact the bullet connectors.  The outside apearance is not important (electrically speaking),  But, the inside should be bright and shiny for sure.  Pull out a bullet connection and look at that.  It should look silvery and shiney, not like a dull grey pebble indicating oxidation.  Dull, flat appearance is metal converting back to where it came from in the earth.  Not your ideal electrical conductor.

Cheers,

[vhenle]

Well I fixed all the wiring in the headlight bucket by removing scoth locks and soldering all connections. I rewired the running lights, they work great! I also replaced an aftermarket ign. button that the PO installed on the handle bars with a NOS switch assembly, for some reason I keep reaching for the handle bars to start it!  Two tired, you where right as always, the missing problem was not caused by the charging system. It started missing again the other day on the way to work, after finding no fire on #2&3 cyl I removed the fuel tank and started the bike while moving the wires conected to the coils. All of a sudden it runs great, no missing. I had the coils off a while back and one of the connectors was not plugged in good. I love when I'm stupid.  Its always the easy thing that makes you look around forever, and I should have known to check there since the mis started after I did the removal. I rode for 5hrs last sunday and the charging system seems to be working fine, thanks for your help and patience. 

Chad

[bryanj]

Dont feel too bad out of the past three engines i fitted i managed to dislodge one of the poits wire connectors bt the rear brake light and the proceded to start the bike trying to figure why it wont stsrt easy then discovering it only running on two! Probably do the same again in the future as well as the old "brain" (or lack of it) tends to forget the old mistakes!