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'81 XS650 Chopper Problem

Discussion in 'The Classroom' started by Russo69, Nov 1, 2020.

  1. Russo69

    Russo69 XS650 Member

    Hey guys, im new to this forum but have been working on my 650 chopper for a little over a year now. Everythings pretty much complete but ive run into this problem that i cant seem to figure out.
    I have everything wired up using a TC bros chopper wiring harness kit. Im not using turn signals, or a horn just the basic components to get the bike running. headlights, tailights, ignition system, kick only. So my problem is that i can get the bike running and riding but maybe an hour or so into riding and ideling the bike will completely die on me and wont start again. troubleshooting this issue myself all signs are pointing towards the stator not fuctioning properlly. When I take a voltmeter to the battery itll read 12.8 volts, if i turn my keyswitch on the voltage will drop down to 12.5 and start decreasing slowly. Now heres the issue, i would start my bike up and try to check the voltage on the battery again but my voltmeter would go ballistic jumping around from 12v to 16v and bouncing from every number inbetween every second. It ended up frying my old voltmeter. Ive also had to replace the regulator/rectifier because the old on nearly exploded on me, it was leaking a fluid and had bubbled up on the backside. So i replaced that and now were here.
    If anyone has any idea whats going on or what I can do to fix this issue that would be great. Thanks!
    gggGary likes this.
  2. Russo69

    Russo69 XS650 Member

    Alright little update. I fired up my bike and ran some volt tests, the battery is still going bananas on my voltmeter, but after turning off the bike the battery reads 10.5v and is charging when it’s not running. Also testing the stator it’s jumping around from .20 to .32 and every number in between. My bike will also rev really high at random but I’m assuming that’s just from the float or something in the carb getting stuck open, I’ll clean that one day lol
  3. Brassneck

    Brassneck XS650 Guru

    Sounds like you have a charging issue. There's a link to understanding the charging system in the tech section and it walks you through verifying your rotor/stator work correctly for the various years these were made.

    My initial thought is perhaps the regulator/rectifier that burnt up wasn't compatible with your 81? I believe they are different pre-'79/80, and post '80/81. Assuming you had an aftermarket combo reg/rec unit that is.
    Raymond and gggGary like this.
  4. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    I'll just say grounds are important, you need a solid ground from battery to frame AND to engine. you cannot depend on engine mounting bolts to be your only ground connection. bush length is a biggy and they do wear out, anywhere Near the wear limit line is too short and yes the charging guide may help you.
    Raymond and Greyandridin like this.
  5. Russo69

    Russo69 XS650 Member

    thanks for the replies guys! im gonna look into that guide and also check out my engine ground because i know theres a black wire that runs from the top of the motor to the top motor mount and thats a little frayed. I'll let ya know how things turn out tonight
    Raymond and Greyandridin like this.
  6. Russo69

    Russo69 XS650 Member

    also i bought the TC bros regulator/ rectifier that plugs right in. before i chopped the bike i was riding it stock for a bit and had no issues until it stopped charging, so i swapped out the entire alternator and reg/rectifier. it ran well afterwards until now
  7. Russo69

    Russo69 XS650 Member

    Alriiiiiiiiiight, I tried following Curlys thread on troubleshooting the problem but I can’t get any readings off of my battery when it’s fluctuating so much. Ive tried 3 different batteries before and they all have this exact same problem. I’ve also cleaned and changed the motor ground wire and cleaned up the battery ground cable but still have the same problem. if anyone can tell me why it might be fluctuating so much and how to fix that, then I’ll be able to move onto figuring out the charging problem.

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