91 dr650s intermittent spark.

Discussion in 'Thumpers' started by Wilderav86, Apr 26, 2020.

  1. Wilderav86

    Wilderav86 n00b

    Joined:
    Apr 26, 2020
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    Hey all.

    I've been trying to diagnose an intermittent spark issue for months now. I've combed through dozens of threads to no avail.

    Ive got a 91 dr650s kick only that will only spark when it wants to. The problem is I am a total dummy when it comes to electricity. Here's what I've done:

    Side stand switch bypassed.

    Ignition switch bypassed with wire jumpers to rule out bad contacts.

    Regulator resistance tested and is in spec.

    CDI has been sent of to regulatorrectifier.com and tested good.

    New plugs, caps, and coil.

    Neutral switch tests good.

    Bench tested the stator and it was grounding to itself. From what I'd read, that is not good so I replaced it with a ricky stator/pickup coil combo.

    Here's the thing, though. When I set my multimeter to audio, I get a beep when I run the probes between the red wire coming from the stator and the frame, indicating the stator is grounded to frame. Also I do not hear a beep when I run from the red wire to the white wire. Is this right?

    I've looked through the wiring harness and cant find anything pinched or disconnected. Nothing seems to be shorting to frame.

    What am I missing here??
    #1
  2. Lewilewi

    Lewilewi Ride it like you stole it......

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    New plug check all connections are tight corrosion free and check earths
    #2
  3. AloneInTheHills

    AloneInTheHills Been here awhile

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    Without wiring diagrams, it's a bit tough to comment, these guys (RMATV) have good basic troubleshooting videos:



    That said, a few basics:

    1. How have you determined you aren't getting a spark? If for example your pickup coil is out of position or not getting triggered you could be getting a spark at the wrong time. YouTube should have videos on pulling out the spark plug and grounding it on the engine case or foot peg and then seeing if it is sparking.

    2. A common cause of issues related to CDIs not working is actually their grounding. Look for the ground from the CDI and make sure it goes to a good wire without a bunch of corrosion, melting, or other damage. Check continuity from the ground on CDI to both the engine case ground lug and/or the battery - terminal. You can also rig up a temporary ground wire for example from the engine lug to CDI ground or battery - if you have any doubt about their quality.

    It's an older bike, with new parts already purchased not resolving the issue. Usually pickup coils and stators don't do intermittent issues unless for example they start a cold engine, but the pickup coil fails when the bike warms to full temp. So, check the two things above and you may find something.

    Also, if you're not familiar the system probably has some charged capacitors like the coil, so be careful as they do store a decent amount of voltage if they've been charged.
    #3
  4. Wilderav86

    Wilderav86 n00b

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    Thanks for the reply!

    I just got the cdi back from testing today and rigged it up. Behold! There was spark! We will see how long that lasts. (Just so we're on the same page, the method I use to test for spark is to ground the spark plug to the motor and kick it over.)

    I've attached the wiring diagram I have been using. The weird thing about this bike is there is no ground lug on the frame or case that I can find. Looking at the diagram, it seems like the main ground is the side stand switch. My theory now is that since the side stand switch has been bypassed, the bike is finding ground somewhere else intermittently. Does this seem reasonable or am I reading this thing wrong? I've wired a new ground directly to the frame and made sure it's legit with multimeter just to rule it out.

    And just to make sure, when I test that the cdi is grounding I am checking between the black wire with white tracer and negative battery terminal, right? DR650wiring_color.jpg
    #4
  5. Beezer

    Beezer Long timer Supporter

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    all those black wires are connected together and tie to the battery neg. what they are not showing is the battery negative to the engine, which will also ground the frame. guessing that is because its kick start only.

    whats weird is that the neutral switch is the only thing shown using a chassis ground (except the sparkplugs). in theory, the light should NOT work without a jumper from the neg post to the frame/engine. (the plugs are in series in a closed high voltage system of their own)

    "checking between the black wire with white tracer and negative battery terminal, right?" yes

    bad connectors can make problems. sometimes they are "cured" simply by taking them apart and putting them back together. I found a weird one last summer... the sockets were cracking because of corrosion. was on a '06(I think) KLR. push on the side of the gastank and it runs, let go it stops... tank was moving the wires in the bad connector to the CDI

    the way the black wires are drawn is the point of confusion. the vertical lines look like a stack of dashes, the horizontal lines are 3 long lines
    #5
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  6. AloneInTheHills

    AloneInTheHills Been here awhile

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    Location:
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    Contact cleaner and inspection of all connections is tedious, but pretty easy work. Running some decent gauge wire to any point on the engine and frame even if temporary will help just to ensure a bad wire somewhere or corrosion of engine mount bolts isn't causing issues since they may assume the engine is mechanically grounded to the frame via mounting. The spark plugs and neutral switch go into the cases, so any clean bolt that goes into the engine will give you a place to supplement grounding. Then if it runs good you know that you can always take them off and troubleshoot your factory ground. Sometimes it's as simple as broken strands of wire in the battery harness itself.
    #6
  7. Wilderav86

    Wilderav86 n00b

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    Well it's been running well for several days now. Fingers crossed.

    I went apeshit with contact cleaner and doused every connection i could find. I guess it was just a bad connection somewhere, be it ground, or a contact. Hopefully the new ground is doing something.

    I was able to explore some local trails over the weekend which was a blast. Clutch is now toast, though. It was on its way out anyway. Hopefully the new clutch plates come before the weekend so I can ride some more.

    Thanks for the help, y'all!
    #7
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