XS400 Charging System and Electrical Questions

[gazampa]

Hi there,

My bikes a 1977 Yamaha XS 400 2E - 2G5 series frame number.

trying to do two things,

1 ) fix an electrical / charging problem

2 ) understand the electrics better

I was out for a ride the other day, bout 60 miles / 2 hours, temperature low 80's, left turn signal pilot went solid after about an hour and a half, small while later the signal fuse melted ( pilots went out ), after about 30 mins, bike running badly - stutters, backfires, power decrease on hills - then stalls. Starts but only goes for about a mile. Checked the battery voltage, 12.4V under 0 RPM and 5000rpm. I have had the headlight off recently when putting on on a new tachometer.

What my Bike Looks like.

Alternator - There's two branches coming out of the alternator, one ending in a female connector containing three white wires and one yellowishy white wire and one ending in a male connector with a black, green, yellow and light blue wire.

Rectifier - On the bottom of the battery. Black grid shaped thing, white wires going in, black wire and red wire coming out. well they look like they are all just going in...or coming out.

Regulator - Its that black rectangular thing at the back of the battery and underneath the fusebox. That looks old. like something off a really old telephone. Initially I did have it confised with the turn relay, a cylinder shaped silver item with a three prong connector from nippondenso which has, ND FN 257E / 12.8 V 85cm / 27W x 2 + 3.4W / NIPPONDENSO / 061300 3572 printed on the side.

Heres what it looks like on paper. XS 400 2E Wiring Diagram

So, Im checking the alternator by the haynes manual method and trying to understand the wiring diagrams, found some colorful ones referenced in other threads.

Alternator Test : ( Using actron CP7665 Multimeter from autozone for all tests )

Checking resistance of each of the three white against the yellow.

Checking the resistance across the green and black wires.

Resistance Readings ( at 80 F - multimeter set at 200Ohms scale ) :

White wires : .7, .6 , .5,

Green and Black : 4.3.

White wires - field coil - ( coming out of alternator ending in a female connector ) - three carrying current from the windings go to rectifier, the last one goes to the turn relay - is this to eventually connect to the ground the turn relay is connected to ?

multi colored wires - rotor - ( coming out of alternator ending in a male connector ) - yellow, light blue, going to pilot box. green going to regulator, black going to left handlebar switches, why is that going there ?

Green going to regulator, Is this the actual voltage being generated input for the regulator.

Also, Is a current from the baterry passed through a winding on the rotar to begin with to induce a field which afterwards is fed by the alternator itself. Or are there permanent magnets.

Rectifier Test. : checking resistance of the red wire and the black wire across the three white wires.

I get no readings going one way and when I reverse the probes while I do get a brief resistance reading, it flashes up on the meter, then returns to the default value of 1 ( which is the value when theres nothing connected to the probes )

I did the test with the diode check function of the meter, I got constant readings of 625 one way and the other way it just stayed at the default reading of one ( when theres nothing connected to the probes ).

Is this rectifier ok ? whats with the resistance reading not being constant ?

Regulator Test : I need to charge the battery up now and do the haynes test for the regulator.

Also, theres a clicking noise when I turn the key in the ignition coming from the battery section, is this indicative of a grounding problem, if so, how do you test the grounds ?

With Thanks.

Adventures in Electrical Systems...Bzzzzzt Ouuuchh !

[gazampa]

I detached everything and polished with steel wool. Took it all off, battery box included and cleaned everything.

Now, the regulator test, the battery is reading 13.8 at idle and 14.2 V under 4000rpm. And, the voltage isnt going any higher.

The clicking is mostly gone except for a slight one by the left hand side panel when the ignition key is turned.

I put inline blades instead of the original fuse box, bit of a clunky fit, thanks to my wiring expertise not being so great.

Removed the headlight and looked at the wires and connections but didnt find anything exposed or blackened even. Im going drive around and use the left turn signal repeatedly to see if anything happens again.