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Vroom's 79 Build Thread- scrambler/brat?

Discussion in 'The Garage' started by Vroom4, Dec 8, 2012.

  1. Vroom4

    Vroom4 XS400 Addict

    Okay, so I did a little bit of searching around and it looks like others have had similar issues and the headlight relay may be the culprit.

    My understanding is the headlight relay prevents power from going to the headlights until the bike is running and creating current via the alternator. Makes sense considering these bikes need all the juice to crank over on the starter. Also, the same power source for the headlight and the gauge lights come from the relay.

    I pulled it and checked out the wires. [​IMG]
    Looked at the wiring diagram and I believe the colors represent the following:
    Black - Ground
    Red - Main power from Battery
    Yellow(supposed to be white:shrug:) - is power from the alternator
    Blue - To the headlight

    All the connections look good. I tested it with the ignition on. Black to Red draws 12.4 volts... so power is getting to it, but not the headlights. I want to try bypassing the relay by just connecting the red and blue wires, but I also don't want to fry something. I didn't get a chance to test the yellow wire with the bike on(but im thinking that would be a good way to check for power from the charging system).

    I'm wondering where I can find a replacement for this or if something else will work...

    Another important note, when I first came across this problem, my neutral and oil indicator lights were functioning. I tried switching the oem regulator back into the system, but then heard a pop and they went out:banghead: Now my entire dash along with the headlights are out.

    I'm a bit confused b/c i looks like they were all powered by the same source. How could the indicator lights have gone out? Also, does anyone know if the gauge lights come on when the ignition is turned on? Or only when the motor is running? I don't remember at this point...
  2. Vroom4

    Vroom4 XS400 Addict

    Thanks. I'm going to try making my own seat pan and seat. I think the design of the bike as is calls for a shorter seat. It'll be retaining the oem mounts so i can switch between the two seats when needed for longer rides.

    I mocked up the new pan this weekend, but more on that later:D
  3. xschris

    xschris a lifestyle not a trend Top Contributor

    your oil and neutral light should be the only dash lights on when just the key is on.
  4. Vroom4

    Vroom4 XS400 Addict

    That's what I had in mind. Thanks Chris:thumbsup:

    So this leads me to believe my indicator lights not working and the headlight could be two separate problems...

    hmmm, much testing to do:doh:
  5. MrStubb

    MrStubb XS400 Addict

    I hate to say this but when you heard a POP!! I'll bet it wasn't Rice Crispies. Sounds to me like you have something toasted either in the regulator or the relay's. I personally don't like working on electricals. It's sort of a dark art to me but I have been forced into it a few times. The first order of business is to get your self a good volt/ohm meter and a complete wiring diagram with values for each component. I would start from the beginning (battery) and work thru to the tail pipes checking the voltages and resistance as you go. You could also start where you made the first modification. Also check for dead shorts in your modified regulator circuit.
  6. Vroom4

    Vroom4 XS400 Addict

    Thanks MrStubb:thumbsup: I'm well past that at this point tho. I've got a voltmeter and tested the wires leading into the headlight relay, though only with the ignition on and not with the bike on. I believe this is the source of my problem since the bike was holding a charge before I swapped out the regulator:banghead:.

    Though, I am a bit confused about the indicator lights going out. That doesn't sound too good, but at least I am familiarizing myself with the wiring. I've combed over several threads and almost know the wiring diagram by heart(btw a huge thank you to all you awesome people out there creating colored versions of the wiring diagrams! Too cool:thumbsup:).

    I've been itching to get back to the bike and continue my testing as I have a few theories brewing:
    1) Need to test the volts coming from the yellow line into the relay with the motor running. This should be a tell tale sign of the charging system as it comes direct from the stator.
    2) I need to bypass the headlight relay and see if the lights come on with just the battery. That will eliminate other problems within the harness.
    3) I need to see if i can swap out the safety relay with the headlight one. I've read this can be done for diagnostic purposes.
    4) I swapped out for the r292 thinking it was for 79 xs400's and older... but I realized that the post says that the r292 is for pre-79 and the r296 is for after 79. So if my bike is exaclty a 79, which should I use??? Should've read that more thoroughly:doh:

    Won't get a chance to work on the bike again till probly this weekend, maybe sneak in some play tomorrow night:laugh:
  7. Vroom4

    Vroom4 XS400 Addict

    Tested the voltage from the white wire(stator to relay) with the bike running. It put out .4 volts at idle and climbed while revving the motor. So this means the charging system is generating a current and sending it to the relay...

    But how many volts does the relay need to trigger the light?

    Also, does anyone know how to test the relay? I read somewhere about using the Ohm's scale and testing for resistance??? Does that sound right?

    Electrical is such a pain... but I'm learning to like it:D
  8. Vroom4

    Vroom4 XS400 Addict

    I've also encountered a new problem...

    The front brake light switch. I swapped out the oem MC for a ninja250 one. The system for activating the brake lights looks simple enough, but as it stands the brake lights are always on... I cut off the oem switch and stripped the two wires, added connectors that fit the two connectors on the new MC, but no go? I also tried jus touching the wires to make the lights go down or up. Nothing...
  9. BamaBill

    BamaBill XS400 Addict

    I swapped my mc for the ninja mc also. previous owner had lost the entire wire & switch. i made a set of wires and connectors and didn't have any problems. maybe another relay?
  10. Vroom4

    Vroom4 XS400 Addict

    Thanks Bill. I'm wondering if maybe the connectors I used were no good? I'm going to pop them off and try it with just the wires together. I'm 99% sure that the brake light is just on right now, so I'll have to double check that the wires even do anything to begin with...
  11. Vroom4

    Vroom4 XS400 Addict

    Okay, so I did a bit more testing and was able to get everything sorted.
    - Headlight relay was shot, so I replaced it with a switch to toggle the headlight on and off:thumbsup:
    - Indicator lights was just a blown fuse:doh: got that sorted
    - Wired in usb properly and it works off the ignition; used bullet connectors with dialectric grease to help keep them connected
    - Rewired Reg and all the connections on new fuse box.

    Still need to make sure the new Reg is working properly. I am seeing that the bike only goes up to about 12.5 volts even when revving it... shouldn't it be closer to 13-14 volts???

    I may swap my oem Reg back in and see if that does the trick, at least that way I'll know the r292 is the problem.

    Didn't get a chance to touch the seat...
  12. Robsteeler66

    Robsteeler66 XS400 Addict

    Sounds really encouraging. I need to figure out my electrical issues. :(
  13. bcware

    bcware Well-read Top Contributor

    Yes indeed.
  14. Vroom4

    Vroom4 XS400 Addict

    Thanks bcware!

    Okay, so my idea of needing 13-14 volts was correct... I'll plug the oem Reg back in and see if that helps.

    Is the amount of volts I am seeing when revving affected by the fact that it's a Lithium battery??? I would think not, but you never know.
  15. bcware

    bcware Well-read Top Contributor

    You should get the same reading even if no battery is present.

    At one point I was riding my largely naked bike around and I managed to knock the battery connection off while riding it in my driveway because it was held on by an alligator clip. The bike ran just fine while the engine was revving and all the lights worked too. As soon as it came back down to idle it died within a few seconds.
  16. Vroom4

    Vroom4 XS400 Addict

    Two new questions:
    1- What is the correct voltage that should be going to the headlight relay from the stator to trigger the headlight?
    2- Where can a new headlight relay be found. I've used the search function but have only seen results from the 80's xs400s, not a '79. Want to make sure I am looking at the right unit.
    3- Specifications for the relay? I'm wondering if any headlight relay will do... they can be found at bennett auto or radioshack, but I'm not sure if they will work.

    I want to determine if maybe the source of my troubles is the stator wire to my relay and not the relay itself:shrug:
  17. Vroom4

    Vroom4 XS400 Addict

    Bump for some answers to help move my build along. Any takers?

    I've come to the conclusion that the charging system must not work properly at idle. If I idle the bike for more than a few mins, the battery drains and it dies, with no chance of starting again. These ballistic batteries are a PITA! They discharge so fast it's almost unusable.

    I may be going back to an AGM...
  18. xschris

    xschris a lifestyle not a trend Top Contributor

    Even at idle the bike should be charging. At 2k rpm's it should be around 14.5v + - .3v
  19. bcware

    bcware Well-read Top Contributor

    Mine does not work well at idle. It will run the bike with no battery for a dozen cycles perhaps before it will die if I disconnect the battery. It's definitely doing something, but mine is not powerful enough to sustain the bike by itself for whatever reason. I haven't really measured the charging system at idle with no battery to get a true reading of the contribution without the battery readings interfering.
  20. xschris

    xschris a lifestyle not a trend Top Contributor

    That is with a battery test. These where never meant to run without one.

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