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Ignition Question TCI vs. something else

Discussion in 'The Garage' started by frenchyinspace, Jan 7, 2019.

  1. frenchyinspace

    frenchyinspace XS650 Member

    3124FEA6-4C23-4B79-BF01-7867806F79E2.jpeg 9F335103-016C-4298-AA45-1599C68C8478.jpeg Hey Everyone,

    After my turn signals went on the fritz, I started pulling the wiring on my ‘75 650. There were a lot of disconnected circuitry including the old turn signal cancelling unit behind the battery etc. A lot of wires leading to nowhere were stripped. I am pretty new to electricity and mechanics, so I also ended up taking off what I later identified as a Hitachi TCI. The reason I took it off however, was that it was connected by both a red and a black wire shortly after the main power output, but also had four white wires connected to nothing. I assumed at first that it was an inactive component. It also looks like something that couldn’t possibly be in functioning order. My Questions are:

    1. Does this thing work or is my XS running on another kind of ignition timing device/mechanism?
    2. I turned the bike over after removing it but didn’t actually start it. Have I ruined the ignition timing and now need to get it retimed?

    Keeping in mind that I don’t understand how ignition timing or TCI’s or points actually function (though I will soon). What should my next step be?

    Thanks in Advance,
  2. 5twins

    5twins XS650 Guru Top Contributor

  3. frenchyinspace

    frenchyinspace XS650 Member

    I think I was mislead by this and similar Ebay listings...
    Another question is, if this piece of equipment was shot, and my bike seemingly ran fine, how could it be necessary/vital to operation?

  4. xjwmx

    xjwmx XS650 Guru Top Contributor

    Either it only seemingly ran fine or it only looked shot.
    mrtwowheel, lakeview and peanut like this.
  5. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

    welcome to the forum.
    If you do not have any electrical troubleshooting skills and experience I would strongly recommend that your 'next step' should be to purchase a handbook so that at least you can recognise the components that you are stripping off your bike. ;)
    Chiltons Yamaha 650 70-79
    The yamaha xs650 Engine and Electrical system Hans J Pahl
    Chiltons Motorcycle troubleshooting guide

    You will also be able to identify the correct ignition components for your model year.

    There are some excellent wiring diagrams and articles in the TECH section that will be well worth perusing. Regarding the indicators this flowchart might be helpful
    xs650 flasher flowchart.jpg
    Last edited: Jan 7, 2019
    frenchyinspace and Paul Sutton like this.
  6. gggGary

    gggGary Stop that! XS650.com Supporter Top Contributor

    Rectifiers are simple AND tough I've seen them look lots worse than yours and work fine. Rectifier testing is also simple.
    frenchyinspace likes this.
  7. 5twins

    5twins XS650 Guru Top Contributor

    A bad rectifier won't stop the bike from running but it will stop the charging system from working. If the battery is charged up, the bike will run for a short while, until the battery charge is depleted, then it will quit running.

    Your alternator generates AC current but the bike runs on DC current. The job of the rectifier is to convert that AC current to DC current. It gets hot while doing this so must be kept cool, usually by mounting it on a heat sink of some sort. Here's one of the rectifiers I linked to above. I mounted it on a section of old computer CPU heat sink .....



    I've been running it for several years now with no issues, total cost less than $15.
  8. lakeview

    lakeview XS650 Guru XS650.com Supporter Top Contributor

    Answer to your question 2
    No, you have not ruined the timing by removing this item and then kicking it over.
    gggGary likes this.
  9. mrtwowheel

    mrtwowheel Honda Etched On Brain Top Contributor

    The most important question is...…….What else did you remove/unwire?

    lakeview and gggGary like this.
  10. frenchyinspace

    frenchyinspace XS650 Member

    Mostly wires on wires that were not connected at one end. This is my first year with this bike and my first time operating on the wiring. The two noteable things I removed were the flasher canceling unit (easily identified), and this, which I now know is a Rectifier.
  11. 5twins

    5twins XS650 Guru Top Contributor

    The thing is, you can't run without a rectifier, at least not for very long, lol. The battery will run down and the bike will quit running.
    Superjet likes this.
  12. XSLeo

    XSLeo XS650 Guru Top Contributor

    You said your bike is a 75, correct? The 75 used a points ignition. Look under the round cover on the upper left side of your engine, your points should be there.
    The 75 wiring is fairly simple. Not near as many electrical devices to remove as the later bikes.
    Up in the Tech section you will find a "Some Wiring Diagrams" link. Follow this link to a list of diagrams. Find the one for the 75.
    Use this diagram to trace the wires you have from where they start too where they go. all your unhooked wires went somewhere.
    Looking at the diagram you can id each unit. Then look to see what color and how many wires come from each unit. Then look at the wires you have and the units you have will help id where the wires should have gone and the units they went too.
    On the 75 the light checker is about the only thing that can be thrown out.
    The rest of the unit's serve a useful purpose.
    I the diagrams thread I like #4. It shows a very basic points ignition, separate reg/rec set up. If you rewire this diagram is very useful.
    This diagram also has squares around it. One is for the electric starter, TCI ignition and the later combo reg/rec.
    I used this as starting point on my 75 when I built my harness. I have made several mods to it. Multiple fuses, relays to power things and such.
    peanut and gggGary like this.

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