86 Aero 50 electrical question

[breaze]

Hi all,
I have an 86 Aero 50 that I believe has some sort of electrical problem. The engine cuts in and out, maintains idle, but is very erratic. The PO mentioned he was having electrical problems and has replaced the CDI and the regulator. Just to be sure, I placed the engine from my 87 SE50 (which runs great) on the Aero and had the same problem. I also swapped out the coil with no change.

So, now I am going thru the electrical tests - so far so good. I suspect the harness itself (there is a melted out ground wire (green) and the ground wire running to the regulator comes directly off the battery instead of out of the harness) but I'm trying to follow the manual. I've completed most of the tests including checking the timing and haven't found anything.

Here are my questions:

The headlight does not come on when it is running. I checked the wires coming off the headlight - I have continuity between the white and green as well as blue and green - doesn't this mean that the actual light is ok?

I also checked to make sure the yellow power wire coming from the alternator has continuity thru to the dimmer switch and that the dimmer switch functions correctly distributing to the hi and lo correctly (continuity from yellow to blue or white). I also checked to make sure the green ground coming off the light has continuity with the frame.

Obviously the alternator and pulse generator are working correctly (since they come from a running scooter with lights working), so does this provide any clue as to what my problem might be?

Any suggestions? Electrical is not my thing.

[mousewheels]

Hi,
Having odd ignition problems *and* headlight problems with an engine you swapped should rule out stator problems.

One thing in common with problems between before and after a swapped engine would be a bad/missing ground connection to the engine (at the starter bolt). There's been a few threads of pretty odd ignition problems due to lack of a grounded engine. If your starter is working fine, a missing ground is not an issue, no need for any further checks. If not - this is a good place to dig in further.

If you have test lamp or DMM AC volts information for stator output on the yellow and white wires it would help diagnose from afar. Reading your troubleshooting, you are working methodically, which can go a long ways, test equipment or not.

[breaze]

Thanks, just to be clear, the engine swap was just temporary in an effort to narrow down the possibilities. Now that the alternator and air/fuel mix are out of the equation I can concentrate on electrical. I've gone thru all the tests in the manual and found nothing awry. Based on how it acts (starts fine, idles, but cuts in and out while accelerating (more so with me on it)), I'm thinking there is a short somewhere - could be one of the switches (thought they tested fine as far as continuity), but my next thing will be to start peeling the wire harness.

I have a DMM but I believe the stator not to be the problem since the working engine had the same experience. That being said, I will take your advice and measure. I understand that the reg/rec takes AC current from the alternator, changes it to DC and regulates it down to what the battery needs (less than 14 volts) to stay charged. Both the yellow and white run from the alternator to the reg/rec - the yellow also runs to the dimmer switch (powering the headlight) and the by-starter so I assume it is DC? Is the white AC?

[breaze]

Well, after going thru the wiring harness, I found the bad connection and the headlight now works. However, there were no obvious shorts and the engine performance hasn't changed.

The starter does work fine so I believe the engine is grounded ok.

In order to read the "AC volts information for stator output on the yellow and white wires", would I just crank the engine and measure each using the frame as a ground?

[mousewheels]

Oh, now that's interesting. In your original post you had gone through and checked continuity from Headlight, through switch and to stator. Also checked ground. Did you find there was a short?

Starter working sure says the engine is grounded.

To measure AC Stator outputs on Yellow/white wires, start up the engine, and probe into the connectors with the engine running. It's easier.

[breaze]

I did check for continuity from the yellow wire terminal at the stator to each of the hi and low beam at the connector to the headlight. I went thru the entire wiring harness today and all I did was replace some of the green ground wires and there connections. To be honest, I am not sure why the headlight now works. Might just be that opening and closing the headlight connection cured it.

I have run so many tests in the last 2 days that I am starting to lose track. I am off tomorrow and will begin fresh in the morning.

OK, so start the engine and get an AC reading for:

1) white connection at stator to frame ground
2) yellow connection at stator to frame ground

Thanks again - this one is starting to get to me

[breaze]

OK, I feel like I'm starting to zero in now - I read a quick tutorial on DMM use and started over realizing some mistakes previously.

First, the AC voltage with the engine cranked from white to engine ground (at alternator connector) is 14 - 15, from yellow to ground is around 9 volts (the engine idle speed is erratic and the voltage varied somewhat).

Significant findings:

1) Leakage test (disconnect neg. battery cable and measure from battery terminal to cable) measured at .04 volts (this test measures in the negative range on my running scooter (87 Elite 50))

2) At the reg/rec the white to green and yellow to green wire terminals measure at 240 ohms resistance as opposed to standard of .1 to .9 ohms, yet at connector coming off the stator, they measure within range (.9 for white and .7 for yellow) - the indication in the SM is to replace/repair the wire harness (yelllow, white, and green)

3) At the CDI, resistance between black/yellow and green wire terminals was around 240 ohms - between black/white and green also 240 with standard for both being .1 to .3 - the indication is to check the coil - the primary coil resistance is high (.5 ohms compared to standard of .1 to .3). Secondary coil resistance measured within range

[breaze]

OK, got it
I checked resistance between the black/yellow wire at the CDI terminal and the frame ground and it read within range. So, obviously the green wire at the CDI terminal is not grounded properly to frame. I measured continuity between the green wire at the CDI terminal and the frame and it was weak but existed. This same weak continuity existed between the green reg/rec terminal and frame as well as between the fuel sensor green terminal and frame - these are all connected together. Then I disconnected the green fuel sensor connection and no continuity existed for any of the 3 locations. Therefore, the continuity with the frame was only achieved thru the fuel sensor connection - obviously these wires are not grounded to the frame.

I connected the fuel sensor green wire directly to the frame - all tests are good and the engine runs well.

Life is good

[mousewheels]

Good troubleshooting and write up, logical thinking, and a fine end result

[breaze]

That's what makes it worthwhile - now if I could only spend as much effort on my job...

Thanks for listening, sometimes ya just gotta talk it out.

[Txaero121]

I know this is a old post So picked up a my 86 aero 50 was checking everything over before my tires come in and new petcock so I can run it !. I was looking at the regulator/ rectifier actually was only looking at it to maybe snag a spare and noticed the green ground cable that hooks up to it was melted by the back taillights had melted upon inspection I opened a good section of the harness up and it the ground had melted a good ways down where it stoppwd was about half way up from the floor pan . The rectifier was a bit corrided I cleaned off the base of it with some sand paper along with cleaned the top where the ground mounts & the frame section under where it mounts bit and the bolt whole .someone on another site suggested the stator could be bad BUT i thought if the stator is bad it would not allow the bike to have sprak .if i am not mistaken When the engine is turning over the flywheel +stator produce power that the CDI converts in the DC to send to the coil to cause spark at the spark plug . i know it has spark i checked that 1st before i found and removed the wire i posted i plan on using a DMM and printing the service manual to check the ohm readings when doing this from what I'm reading the bike has to be on and running. I'm going to go through and check all the grounds .
When you say you connected the green wire from the fuel sender to the frame . Did you do that off the harness itself? Or off the sender or both ? Bc 1 plugs into the other right ?

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