2003 640A running fine then... Not.

Discussion in 'Thumpers' started by flashover604, Apr 4, 2013.

  1. flashover604

    flashover604 tailgunner

    Joined:
    Nov 27, 2006
    Oddometer:
    647
    Location:
    Ohio
    Hi all. After a six month distraction due to an apparent need to incur some new hospital bills, I've taken some time to try to get to the bottom of a gremlin from last year.

    I took the bike to Hatfield and McCoy, did a couple hundred miles of trail, trailered it home, all is good. Didn't have the first problem on the trail, but twenty miles away from home, problem. I knew I was going to hit reserve before I hit the gas station so once I hit a nice straight spot with no-one behind me I reached down, switched to reserve, went about 100' and it felt like someone turned the key off. I pulled in the clutch lever for some reason, even though I KNOW that I have a Rekluse clutch. So, once rpm dropped to nothing, I was done. I coasted into the rest-stop that was luckily just up the road, pulled up under a big oak tree, parked the bike and cussed. A lot.

    I have a just-about-gone sprague clutch spring, so I kicked the snot out of it, but never got a hint of fire. A buddy came and picked me up and dropped me off back home. Later that night it fired first kick.


    Here's what I've checked...

    Tore carb apart, thought maybe I sucked something into the jets. Nothing.

    Checked all connections under seat, nothing found loose, broken, suspect.

    Checked ignition switch for the common broken wire/solder joints. It looks like it just rolled out of Austria. Perfect. I filled the void with silicon to prevent anything breaking down the road...

    After reinstalling the carb I've ridden it a couple times, less than five miles each because I don't want to be farther than I want to walk if it does it again. It seems to run fine but I can't shake that "When is it going to strand me again" feeling.

    Any ideas?
    #1
  2. robberst

    robberst Been here awhile

    Joined:
    Jun 5, 2007
    Oddometer:
    178
    Location:
    North Dakota
    I've had a similar thing happen

    The vacuum line to the fuel pump was split. It had a braided sheath over the rubber hose and it was difficult to see it's condition. I took the fuel pump apart and found it filled with crud. cleaned it and replaced the vacuum line and all was good. It would run fine until I got close to reserve then.....run out of fuel.

    One time this happened a battery terminal vibrated loose at the same time. It would turn on, lights on, but the loose terminal couldn't carry the current load of the starter motor.
    #2
  3. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    5,140
    Location:
    N.V.I, B.C.
    Sometimes when you switch from main to reserve if the pump diaphragm is weak it may lose it's feed... The next time this happens try pressurizing the system by blowing pressure into the tanks vent tube to help advance the fuel and then try starting...

    Have a look under the dash at the wires tied to the dash support bar... You will have to undo the clips holding them to the bar and check for rubbed wires which may be grounding out...
    #3
  4. flashover604

    flashover604 tailgunner

    Joined:
    Nov 27, 2006
    Oddometer:
    647
    Location:
    Ohio
    How long do you think it'd run with just the fuel in the bowl? It literally went less than a hundred feet then nothing. No spit, no sputter, not one attempt to fire. It seemed like I either lost ALL fuel or ALL spark.

    If I lost all fuel from the tank for whatever reason, I figure it'll run a quarter mile or so.

    Thanks for the ideas, I'll give them a look. Keep 'me coming!
    #4
  5. gunnerbuck

    gunnerbuck Island Hopper

    Joined:
    Nov 19, 2005
    Oddometer:
    5,140
    Location:
    N.V.I, B.C.
    I took off today and forgot to turn on the fuel tap, It went about 100 meters and then started to die, but I was able to get it switched before it totally died... Unlike your bike I had the engine stutter to give warning...

    All you can really do is go over everything that is obvious and hope you have it fixed..


    One other thing that can do that mystery shutdown thing is a failing pulsar coil... It will sometimes do that a couple of times until it gives up completely...
    #5
  6. flashover604

    flashover604 tailgunner

    Joined:
    Nov 27, 2006
    Oddometer:
    647
    Location:
    Ohio
    I had that in mind as a possibility. I seem to remember reading about them running fine until they get hot then let go until they cool.
    #6
  7. SRG

    SRG SRG

    Joined:
    Nov 18, 2004
    Oddometer:
    1,578
    Location:
    Charlottesville, Virginia
    Check that vac. line mentioned above. Mine had a kink that would close up and the bike would die.
    #7
  8. flashover604

    flashover604 tailgunner

    Joined:
    Nov 27, 2006
    Oddometer:
    647
    Location:
    Ohio
    I pulled the dash and removed all the zip ties. I traced every wire I could get my fingers on to check for chafed wires. I found a couple that had spots worn thought the insulation by larger gauge wires, but nothing that ended up as copper on copper or copper on metal. I vinyl taped them up and isolated them to keep from rubbing. I disconnected all of the connectors under the dash and put a little dielectric silicon grease on each individual contact. I never found a smoking gun, but things should be fairly clean now. I checked the petcock to fuel pump hose. I didn't have any kinks, and it does not have any leaks. I did not remove the pump and check the diaphragm. I fired it up on the second kick after six months of sitting. I took a 20 minute ride to a buddy's house, hit some rough woods then rode back. Not a hiccup. I guess I'll ride it and see. IF it does it again, I'll check the pump diaphragm and the pulsar coil. Thanks for all the help guys.
    #8
  9. bmwktmbill

    bmwktmbill Traveler

    Joined:
    Jul 16, 2005
    Oddometer:
    5,608
    Location:
    Traveler
    I'd check the fuel flow at the petcock in the run and reserve positions.

    Just in case the problem starts there.

    Maybe you have?


    bill
    #9
  10. flashover604

    flashover604 tailgunner

    Joined:
    Nov 27, 2006
    Oddometer:
    647
    Location:
    Ohio
    I drain the fuel into a five gallon can when I am going to remove the tank. I checked both ON and RESERVE as it was draining. It seemed to flow fine on both, certainly more than the engine could use at full throttle. I don't know... Maybe it DID suck something into jet that fell back out. I didn't SEE anything, but who knows. I went for a quick twenty minute ride again tonight with no trouble. Now, I guess I'll just have to aim it towards work and hope it gets me there. Wish me luck...
    #10