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79 xs650 stopped running on me.

Discussion in 'The Garage' started by JE4570, Mar 10, 2019.

  1. JE4570

    JE4570 XS650 Member

    17
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    Ohio
    I just picked it up about a month ago. I was out riding with my friend. I started accelerating from stop and got to about 50 mph. Then the bike seemed to want to die on me. So I pulled in the clutch and the engine died on me. I feathered out the clutch and it started again in a roll start sort of way (probably bad for the bike) and it didn’t seem to want to give me power. I heard a loud pop like a gunshot accompanyied by black smoke (according to my friend) and that was the end of the bike wanting to run for me. I pulled over and couldn’t get it started so I trucked it home.

    I immediately checked compression as I was scared the timing chain got messed up, but I had 150 psi in both cylinders. I then checked the points. They were way off

    After learning that, I started from ground zero and set the cam tensioner and then measured the point gap and set the timing. It still wont start and I am kind of thinking its the carbs now.

    I am currently charging the battery as it was a little low from trying to start it on the side of the road. Hopefully my carb issue isn’t electrical.

    Any ideas on helping me diagnose? The bike has been running relatively well for the past few weeks other than constantly needing to adjust idle speed screw based on the temp outside.
     
  2. xjwmx

    xjwmx XS650 Guru Top Contributor

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    Only a small chance of that. All seriousness aside, could be about anything. Early on I had basically two stuck valves in my carbs that mimicked what you're seeing. Did you rebuild the carbs? What parts did you use?
     
  3. Jim

    Jim "No...Try not. Do ... or do not. There is no try." Top Contributor XS650.com Supporter

    Welcome to the forum!
    You have compression... that's good. I'm assuming you did a static timing, since it won't run. That should be close enough to make it run. Next thing I'd do is spin it over and see if you have good sparks from both plugs... then go from there. If you have good sparking on both sides, then yeah.... prolly fuel related. It's a fork in the road. That simple test will let you know which path to start down..... fuel or ignition.
     
    mrtwowheel likes this.
  4. JE4570

    JE4570 XS650 Member

    17
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    Ohio
    Hi,
    Thanks for the responses. I haven’t touched the carbs since but I guess I will go ahead and order a rebuild kit. I think I was having trouble with them since the beginning as I get a fuel leak if I leave it parked with the fuel on. I will probably mess with it in the morning to make sure its spark is good.
     
    Jim likes this.
  5. xjwmx

    xjwmx XS650 Guru Top Contributor

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    We usually recommend against kits. You can get the needle and seat made by Mikuni (carb OEM) still. Probably all you need, especially from among the stuff that's in kits. You might need floats...
     
  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    My money is on the spark advancer...
     
    Jim likes this.
  7. Wulfbyte

    Wulfbyte XS650 Enthusiast

    Check all your electrical harnesses too! Loose connections can cause that problem ,just happened to me same scenario,tracked it to my main harness was loose inside my headlight! Did all the tests like you did thinking something major just happened! While I was troubleshooting noticed that it when I did get it started back it would be fine the turn my bars a bit and it would happen again! Also a couple of rides before that I started noticing a backfire on decelerations thinking I was having some carb issues, after I plug harness back in all the way no problems at all, took a 70 mile trip today, weather was great, bikes everywhere ,it was great to see! Hope your problem is something simple! Good troubleshooting to ya and welcome to the site,whatever problems that you’ll come across you’ll definitely find the answers!
     
    Moabite likes this.
  8. xjwmx

    xjwmx XS650 Guru Top Contributor

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    Not unless his gas leak is from there...
     
  9. 5twins

    5twins XS650 Guru Top Contributor

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    These are old bikes so you have to go through them and pretty much check everything when you get one. As mentioned, check/clean/lube your mechanical advance unit and the rod it mounts on that passes through the head. Most haven't been serviced since they left the factory. Many are all dried out and stick in the advance or retard position, or both. Check your spark plug wires and the connections on both ends. The plug caps may be loose, or the wire to coil connection. The connections could also be corroded and bad. Installing new plug wires and caps is one of the 1st things I do on one of these. Or at the very least, I install new NGK plug caps and re-do the connections at both ends of the plug wires.

    You said you re-set the points. If you got any oil at all on the points faces (from the feeler gauge), that can foul them. They may need to be cleaned.
     
    TwoManyXS1Bs and Moabite like this.
  10. Machine

    Machine Race the wind

    Just how low was the battery ? Next time you have it running try to confirm you engine is actually charging the battery. ?
    Reading how your bike died "seemed to want to die on me" with a backfire too reminded me of when my own died of a dead battery after it quit charging.
     
    Wulfbyte likes this.
  11. JE4570

    JE4570 XS650 Member

    17
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    Ohio
    Ok so I actually think it is the advance at this point. I cannot for the life of me set the points. They keep getting off or dont make sense. I set the gap and its all over the place. I put a pamco on my last bike (a honda cb350) and I feel like it may be a good option for this one. Any tips on setting points. I watched a motorcycle nuts video on YouTube but that method doesn’t get me far. Is there a better method to get it set correctly.
     
  12. Jim

    Jim "No...Try not. Do ... or do not. There is no try." Top Contributor XS650.com Supporter

    Pull the advance cover and put some pics up here.
     
    TwoManyXS1Bs likes this.
  13. Mine does that when it runs out of fuel.
     
  14. JE4570

    JE4570 XS650 Member

    17
    8
    3
    Ohio
    I i am confised by why they dont want to fire correctly. I am using a feeler gage when they are open and then adjusting the screws I circled. My advancer turns freely and then gets a little tight for a second then turns freely again is this normal or do I need to take it off and clean what it sits on?
     

    Attached Files:

  15. JE4570

    JE4570 XS650 Member

    17
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    Ohio
    Stupid me needs to go read my clymer. I didn’t realize the advance was on the other side of the bike. I assumed that it was behind the points like it was on my cb350. Let me get me back to you after I check it out
     
    Jim likes this.
  16. JE4570

    JE4570 XS650 Member

    17
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    Ohio
    Ok so my advance looks pretty rough. There is like a clip thing that holds one of the weights to the pin missing. Sorry for the bad lighting its late. I honestly feel like buying a pamco and not dealing with this headache.
     

    Attached Files:

  17. azman857

    azman857 '80 XS 650SG Rider Top Contributor

    With the latest model of PAMCO's you can rid your bike of the ATU and the points plate in one assembly. Still need the shaft and bearings but that's OK.
     
    gggGary likes this.
  18. Jim

    Jim "No...Try not. Do ... or do not. There is no try." Top Contributor XS650.com Supporter

    Yeah.... you gotta mess there. Just at a glance.... as well as the missing clip....
    Red arrow: weight is retracted.
    Green arrow: weight is extended.
    White arrow: replacement spring... prolly wrong size.
    Yellow arrow: too much wear on the tabs. No sign of it ever being lubed.... yeah... a mess.

    image.jpg
     
    TwoManyXS1Bs, Machine and Moabite like this.
  19. Jim

    Jim "No...Try not. Do ... or do not. There is no try." Top Contributor XS650.com Supporter

    If you go Pamco, buy direct from Pete. Mikes XS is selling a chinese knockoff that is NOT a Pamco.
     
    Mailman, mrtwowheel and Machine like this.
  20. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

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