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1978 xs650 ran perfect, now it won't even fire. Need diagnostic help

Discussion in 'The Garage' started by WolfDesigns, Dec 3, 2015.

  1. WolfDesigns

    WolfDesigns XS650 New Member

    Hey guys. First post to the forum. I've managed to get pretty Far on my own, but I really need some help.

    My bike is a 78 xs that that I built completely from scratch. I've attached a picture, but don't know how to make it visible otherwise. It was sold to me in non running condition and missing some of the parts needed to make it run( ie exhaust, bars, etc) but it is an extremely clean lower mileage bike.

    Upgrades I've done to the motor:
    -mikuni vm34 carbs
    -Boyer Bransden electronic ignition.
    -new coil, new battery, rectifier.
    It ran awesome at this point, fired on the 3rd kick after who knows how many years. I tuned the carbs and once it was smooth I took it for a around the block with no issues, until the battery died( stator no longer charging)
    -added xscharge pma and a new rectifier, charging problem fixed and bike running awesome.

    Had a few shake down runs under my belt then the keyway that holds the alternator rotor on loosened up and caused the rotor to wobble. So I bought another one and installed on the bike. Set top dead center, ran awesome again. Not one complaint. Here's where I get confused.

    After returning from thanksgiving vacation. fired the bike, ran amazing so I didn't make any adjustments. Next day, headed out for a run to the beach but it will not start. Battery, fuel, everything was how it should be yet still wouldn't fire. I would get a few sputters as if it wanted to go, but no catch. I've checked every single thing that can be checked. All wires, grounds, battery, coil, spark plugs, everything. I've adjusted the timing to advanced and even retarded, checked top dead center numerous times, new plugs. I've adjusted the carbs to see if I could get anything, still no fire. I'm at a loss, has anybody run into this issue or have any ideas to what it could be?

    I've got around 200 miles on the bike. And I can't figure out how it went from running to not in less that 12 hours. Any help is appreciated, really really appreciated because at this point I don't know if it's electrical or mechanical

    Attached Files:

  2. figure8

    figure8 XS650 Guru

    Have you checked all your ground connections?

    Spark is strong?

    Gas is getting to carbs?

    Float level in carbs?

    You're running a PMA, is the headlight switched off until running?

    I know you have but these my thoughts off the top of my head. That's where I would double check.
  3. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi Wolf and welcome,
    first, does it spark?
    Next, is the spark in the right place?
    If that's yes and yes, it's gotta be fuel.
    Pull the carbs, give the inlet holes a big shot of instant start, and try to start the engine.
    You should get a brief vroom to verify the ignition is working.
    Then do the good ol' XS650 carb triple clean.
  4. Yoozy

    Yoozy XS650 Addict

    Kill switch buggerred?
  5. WolfDesigns

    WolfDesigns XS650 New Member

    Hey guys. I'm still getting sork and fuel( but could very well be float level still) has anyone run into any issues with the elctronic ignition? Maybe something got fried?
  6. figure8

    figure8 XS650 Guru

    It's not out of the question that something could go bad with the ignition. But for a quick test, take the carbs off and check the floats. Clean if necessary....you're running a Boyer so I'm not as familiar with those.....
  7. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Hi Wolf,
    if there's still big fat blue sparks we are down to checking the ignition timing and then doing the ol' carb triple clean.
    ESPECIALLY the enrichening and slow running systems.
    They have the smallest passages so they are the most likely to get blocked and the ones that are needed to start the engine.

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