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wont start, backfires if kicked with throttle open HELP!!

Discussion in 'The Garage' started by Wilkopotamus, Dec 7, 2012.

  1. G'day All,

    Hoping for some advice from the collective gurus out there!

    I'm building a 74 TX650A Street Tracker and have installed a Pamco coil, running the ultimate coil and iridium plugs (Mikes XS). I have freshly rebuilt Carbs (BS34) and have not touched the timing or valve train.

    The bike was running and starting beautifully, took it for a ride 5ks up the road it died as if it had run out of fuel - plenty of fuel, drained the battery trying to start it, refused to start under kicker. Pushed it home and found that it had no spark - replaced PAMCO ignition, now has great big fat spark, but I can't get it to start??? Have recently checked float height - adjusted it to 25mm. Carbies are clean and fuel is fairly new.

    I'm racking my brain as it was idling and riding well before it stopped!

    Cheers Josh
  2. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

  3. Kingwj

    Kingwj I know nothing, nothing!

    New plugs, always the first thing to do. Never saw an engine crap out plugs faster than the 650 Yam.
  4. G'day Pete,

    No PMA, running new reg/rect from Mikes xs and new battery. Checked both plugs and they are producing large fat spark!

  5. pamcopete

    pamcopete Ride.Enjoy.Life is Simple


    Well, if it is ignition related, then being as you have a big fat spark, it would have to be timing, like one of the three locating pins is missing. Check the installation instructions for the advance system on the web site www.yamahaxs650.com and account for the three locating pins.
  6. Will do, do these have a habit of shearing in operation? I haven't had to mess with my auto advance as it was operating fine when I installed the PAMCO.
  7. all 3 locating pins are in place, bike backfires through the carbs if I open the throttle while trying to start the bike.
  8. FLEA

    FLEA XS650 Junkie

    might be worth checking your advance/retard.
  9. XSLeo

    XSLeo XS650 Guru Top Contributor

    On your Pamco rotor, are any magnets missing?
  10. Hammer-N-Anvil

    Hammer-N-Anvil 70's Style Chop

    Pamcopete, I too am having the same issue only I am running a PMA.
  11. cleoncleon

    cleoncleon XS650 Addict

    I would TEST your Pamco, too see if it was destroyed by the PMA system..
  12. XSLeo

    XSLeo XS650 Guru Top Contributor

    Most XS650's don't like it when you hold the throttle open while starting. Just leave it alone.
  13. Hammer-N-Anvil

    Hammer-N-Anvil 70's Style Chop

    okay so I believe the PAMCO ignition is okay. After 2 days with no sign of life the bike kicked over just fine this morning. Adjusted carbs a little for idle and some backfire, as I just cleaned them. Once I flipped the switch to turn the lights on, the bike died. It had been running for 10 mins prior, which it normally strains a little under the load once first turned on. and it didn't really want to start back up after that, lights turned off and all. Am I not getting enough juice? I feel as if the lights pull too much power from the coil and therefor the engine doesn't get enough spark??

    to be completely honest I have no clue what I am doing, have done, or where I am going. I'm just making it all up as I go, with a little help from the web and forums

    Any advice is appreciated
  14. angus67

    angus67 Welder's penetrate deeper!!

    i hope your pointing a box fan at the motor if your idling it for 10 minutes.
  15. Hammer-N-Anvil

    Hammer-N-Anvil 70's Style Chop

    had plenty of cross draft with backdoor and garage door open (blowing all exhaust steadily out, thinking this was enough for cooling). at least i think there would have been plenty with a cool Texas winter breeze blowing through. if not, do you think this could have been the reason for dying out this go around? I'm pretty close to just buying a completely new Pamco/PMA system for the bike and doing a complete re-do on it as the guy who originally built the bike did some Frankenstein shit
  16. XSLeo

    XSLeo XS650 Guru Top Contributor

    Hammer, When you get it running do a voltage check on the pma output. At the cap or battery, whichever you have. At idle without lights on the voltage should be 12.5 to 14.5 volts. With it reved up to around 2500 to 3000 rpm it should read 14.5 volts and never go above 14.5 volts at any rpm. If the voltage is low then your reg/rec isn't working well. It might be a weak or bad ground.
    Also test the three wires from the stator on the AC volts scale. Test the three wires as three sets of two. The AC voltage should be around 10 to 20 VAC at idle. Maybe up to 30 VAC at higher rpms.
    Before throwing a bunch of money at it do some testing to find out just whats not working.
    Check the wiring of the PMA to the reg/rec and from there to the battery/cap positive and negitive. All your grounds. If the voltage with out the lights is less than 12.5 volts the spark will be weak. When you turn on the lights the voltage drops even more, the sprak gets too weak or stop entirely then the engione quits.
    One thing I might suggest is to hook up a battery to just the ignition. Leave the PMA wired as it is. This way the battery powers the ignitrion and no matter what the pma or lights do the engine will stay running.
    This is the best way to test a PMA for function. If the PMA output is unregulated it can send out 20+ volts to the rest of the system, blowing bulbs and electronic ignitions.
    Your PMA may be ok, just a bad reg/rec.

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