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Thread: Fixing Earthing Problems - Why and How

  1. #1

    Fixing Earthing Problems - Why and How

    This is a very general topic so I put in the most read forum even tho the subject bike is a Uly - sorry if that's not right, and can someone tell me how to get rid of the thumbnails - jv

    A light throttle/low speed/moderate rpm cough or hiccup or misfire or stutter or pop or whatever you want to call it (to copy Lunatic), is a common problem on XB’s. (See his comments 4th post down on A big part of the fix is cleaning up the earthing joints from the wiring loom. What is not discussed much is WHY the corrosion causes so much trouble, or HOW to fix it so it doesn’t come back again.

    The basic reason the earth joints corrode is because aluminum is actually a very reactive metal. It only seems unreactive because its covered by a thin film of nonconductive oxide, which must be breached at any electrical joint. Where aluminum touches another metal with a different reactivity (like low reactivity copper, tin, lead or their alloys) in the presence of a bit of moisture, it sets up an electrolytic corrosion cell with its own small voltages, a bit like a thermocouple. Where 2 aluminum surfaces touch and are made to carry a current (like the earth return current from starter motor through the engine and frame), that also promotes corrosion when wet and/or salty.

    Using the frame to do double duty, carrying the earth return current as well its other functions, is the way Erik Buell designed the Buell. Electro-chemically, it’s just not a good idea.

    In airplanes it can’t be avoided; every ounce matters. They don’t run extra ground wires and don’t normally have corrosion problems, so there must be a way of doing it properly. An RNZAF Avionics Engineer told me earth wires must have a resistance of less than 0.7 Ohm, otherwise stray voltage drops can be set up, that affect control computers and other electronics. Steps on how to do it properly are in the HOW section below.

    The bit about ‘...stray voltage drops … that affect control computers…’ is important for the misfire/stutter/hiccups. The ECM reads voltage drops across the various sensors. Most sensors have their own earth return loops in the wiring harness, but 2 sensors do not; the Engine Temperature sensor and the O2 sensor. Both are earthed through the engine. If there are electrical joints that have high resistance (corroded) or if there are induced voltages, like you get in metal close to induction coils (e.g. the ignition coil mounting bracket), then the ECM reads not only the voltage drop across the sensor, but the additional drop across the dirty joints and/or any addition or subtraction of induced voltage. If this varies (as induced voltages do, or the resistance of dirty joints does when stressed by engine vibration, road bumps etc), then the ECM ‘sees’ the sensor voltage changing and compensates for it.

    It’s the ECM compensating that causes the misfire etc. I believe this is why people swear an earth wire to the ignition coil mount stops misfires, when in any normal electrical wiring sense there is no need for it, as discussed here:

    Also, electro-chemically, you should not rely on ANY current path through aluminum if you can avoid it. Pure aluminum is a very good conductor of electricity, but its alloys are not. That, plus joints that corrode, is why you should not run earth return currents through it.

    And there are a few dodgy joints. You need to disassemble the rear end of the bike to clean the joints between the subframe and the main frame ‘…back to bright metal’, and then they are not easy to protect from road spray. For XBS's the joint between the halves of the subframe also carries current. Also, the connection from the subframe to the battery negative cable is shrouded by the cadmium plated steel battery tray. You should remove the battery tray to clean that joint properly, but most people won’t.

    You can avoid all these issues by running extra earth cables/wires. The major one is a 4Awg (20mm2) cable from the frame side of the braided earth strap, at the top anti-vibration mount above the engine, back to the battery negative terminal.
    image (12).jpg image (11).jpg
    Note the two extra wires in the lug at the anti-vibration mount end in the RH picture above; one runs forward to the earth point on the steering head, and another shorter one, connects to the rear coil mounting bolt.

    This means all earth return currents from the rear cylinder head back to the battery are carried through copper wires and nickel- or solder-covered copper or brass lugs, directly to the lead negative terminal. All these metals have close enough reactivities, so corrosion cells are not an issue.

    The earth return current from the lights, horn and instruments also flow through low reactivity joints and any induced voltage in the coil bracket is quashed. A short wire between the 2 bolted earth points in the left-hand side of the rear subframe as shown on a Uly below, means other sundry earth return currents, are also routed through low reactivity joints. Edit: XBS's have the ECM grounded on one side of the rear sub-frame and the battery on the other. That makes an extra earth wire between the ECM ground point on one sub-frame half and the battery negative cable ground point on the other side VERY VERY important.
    image (14).jpg
    All these earth joints are still connected to aluminum, but don’t NEED the aluminum as a current path.

    If you were OCD about it, you’d run an earth return from both the Engine Temp and O2 sensors, but engine vibration would be a problem and the above works. However, if you suspect a dud ET or O2 sensor, maybe try earthing it directly before replacing it??? Edit:Like this 2nd last post on this thread
    Attached Images Attached Images
    Last edited by John Vreede; 09-01-2018 at 11:00 PM. Reason: Added Lunatic link

  2. #2
    The Airforce earth bonding method is as follows:
    • Clean all contact surfaces with Scotchbrite or ~240 grit sandpaper, back to bright metal. Edit : Don't remove the tin/solder or Nickel coatings from the brass or copper lugs as the coating serves a purpose in isolating metals of different reactivity
    • Spray all contact surfaces with a cleaner/corrosion inhibitor that “…improves electrical properties”, like CRC 2.26. (Edit: it actually does! - I dipped a penny in it and it removed the tarnish)
    • Torque up the joint while the contact surfaces are still wet with the cleaner/corrosion inhibitor.
    Edit: As Cooter pointed out below, there is a time element here too. Clean, spray and torque up quickly, don't clean one day and spray and torque up the next.
    • Clean off the exterior of the joint with contact cleaner (CRC Brakleen or carb cleaner works too).
    • Spray the joint with a waxy corrosion protectant like CRC CPC400, to stop water seeping in and corroding it again.

    'Clean all contact surfaces … back to bright metal’ (e.g. on the braided earth strap) means cleaning:
    • the engine and frame surfaces where the joints bolt up (at least on the engine side)
    • both sides of each end of the dog-bone link
    • the new earth cable lug
    • as well as both sides of each end of the braided strap itself.

    A tap into the threaded holes and cleaning the underside of bolt heads and their threads and washers is not strictly necessary now, because the bolts and the frame or subframe don’t need to carry any current. Loctite on bolt threads won’t affect joint conductivity either. However if you don't want to add extra wires then the bolts and washers and thread all carry current and must be cleaned and Loctite will affect the resistance of the joint. (see the checklist in for additional things)

    I’ve only found 5 earth joints in the standard wiring on a Ulysses:
    • Two bolted inside the rear cast subframe,
    • One at either end of the braided earth strap between the frame and cylinder head bridging the dog-bone anti-vibration mount above the engine,
    • One bolted to the front of the steering head.
    Edit:Also the connectors between the ET and O2 sensors' wiring and wiring harness count as earth connections and the ECM fuse in a way also - if corroded they will produce voltage drops that act the same as corroded earths to the frame.
    • Other XB’s have slightly different arrangement of earth points (see & where Lunatic talks about 3 different earth wire positions at the front of the frame)

    Sizes & lengths of extra cable and wire for a Ulysses are:
    • Cable from braided strap to battery negative = 20 - 25mm2 cross section and 29” long (eye centre to eye centre). Check length on other XB’s (shorter frames and/or different subframes).
    • Wire to steering head earth bolt = at least 0.75mm2 cross section and 36” long + however much is in the connectors.
    • Wire to rear coil mounting bolt = at least 0.75mm2 cross section and 12” long + connectors.
    • Wire between subframe earth points = at least 0.75mm2 cross section and 6” long (eye to eye). Check on XB’s with different subframes.
    • The cable I used was a 20mm2 earth cable from a small-car wiring loom (free from a wrecker). It already had a brass lug crimped and soldered on, to bolt to the battery. I cut it to length and got an auto electrician to crimp and solder a lug on the other end.

    Crimp-on lug:
    • get one sized for the cable + 2 extra wires, with as big a surface area around the 5/16” hole as you can.
    • get it soldered as well as crimped (belt and braces).
    • Heat-shrink a sleeve that has glue inside it, over all 3 wires, to strain-relieve the 2 smaller wires so they don’t break from vibration as in the RH photo above.

    Spraying CPC400:
    • use cardboard behind the joint to give room to allow the spray to get to the back of the joint and rags or paper to catch the overspray.
    image (15).jpg
    • use a heat-gun/hair dryer between coats to flash off the solvent, to build up the film thickness.

    Edit Added: Moarant posted this, which shows that doing continuity testing didn't pick up that the earth to the ECM was bad. Through some inspired guesswork he figured the ECM earthing was the problem and added an extra earth wire spliced into the ECM earth leads and running directly to the battery, which cured his problem.
    There are 2 possible causes I can think of for this:
    1. Since the bike is a Lightning and the ECM earths on the opposite side of the subframe to the battery, that the joint between the sub-frame halves was corroded - fix with a wire between the earth points like on my Uly, or
    2.That the crimp on the earthing lug was bad. I measured the resistance of my earth wires from the black ECM plug back to the sub-frame lug and found 7 Ohms resistance, however my misfire was cured by the earth cable and the high resistance crimp didn't seem to be part of that problem. After measuring, I did spray that joint, including the crimp, with CRC2.26 and since then the resistance has been lower every time I've measured it. That could be my poor measuring technique, but might also be the effect of the CRC2.26. I got an electrician with a Fluke DMM to measure it again today and the the resistance is back to near zero (as it should be) - so I won't be changing that crimped lug - but will keep an eye on it.
    Whatever be aware that crimps can go bad over time if they weren't made right to start with and be a source of voltage drop, which could cause a misfire like it did for Moarant. You'll only pick them up by measuring their resistance with a sensitive DMM, not by continuity testing.

    My ‘07 Ulysses had an intermittent misfire that was 99% fixed by running the earth cable from the braided earth strap to the battery negative and cleaning/corrosion-inhibiting both ends of the braided earth strap joints and both battery terminals as above (the last 1% was fixed by richening the mixture). The extra earth wire to the ignition coil mounting bolt didn’t make any difference on my bike, but probably would have if I hadn’t put in the earth cable and cleaned all the joints. However, because it’s so important to quash stray voltages, which may even be between parts of the engine, I did it anyway. I believe you should too.

    In an ideal world, Buell’s stock earth wiring works. But, as many people have found, if the bike starts to misbehave you have to clean the earth connections; the method given will clean and protect the standard wiring loom connections properly. Probably, just applying the Airforce earth bonding process to the standard wiring earth points would be enough in most cases. However, that still won’t improve the joints between the subframe and main frame and may not be enough to suppress induced voltage effects on the Engine Temp and/or O2 sensors. The earth cable from the braided strap, and the earth wire from the coil mount, are effective for this - jv

    Edit: there is now a checklist of the above on this link
    Last edited by John Vreede; 09-30-2018 at 08:35 PM. Reason: Additional info and checklist link

  3. #3
    Senior Member
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    Jan 2016
    Um yea..... clean your "ground" connections, coat them so they stay clean. Much shorter post. Same result.

  4. #4
    Join Date
    May 2014
    I just sprayed silicone contact protective spray on them.

  5. #5
    Senior Member rchuff's Avatar
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    Apr 2012
    Willow Grove, Pa
    Let me give you a tip, when you type a novel most of us won't even bother to read it. Dielectric grease works well.

  6. #6
    Senior Member Silverrider's Avatar
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    Sep 2016
    Quote Originally Posted by TPEHAK View Post
    I just sprayed silicone contact protective spray on them.
    Teabag were you out of Teafoam ?
    Last edited by Silverrider; 07-27-2018 at 01:33 PM.

  7. #7
    Senior Member Cooter's Avatar
    Join Date
    Dec 2012
    Crawling up your skirt
    Thanks JV for the detail Although it's entirely overkill for a motorcycle you did hit on the most important points that are not usually discussed in the multitude of 'clean your-grounds' threads.

    Once you clean your aluminum ground contact points, re-assemble them quickly and coat with a protectant layer. Just like a quality TIG weld, the aluminums reaction to atmosphere (building the oxide layer) inhibits electrical flow as well.

    CRC 2.26 is really good stuff! (Way better than seafoam) In a lazy moment someone who looks just like me has hosed out a right handlebar control just to get the starter button working ()

    With (-) ground DC systems, the grounding path rule is always bigger and shorter is better.

  8. #8
    Thanks for taking it as intended. If you know this stuff then I agree, its too much to read, but if you don't, then you could be glad for the extra detail.
    You never truly understand something until you know 'why', then you can evaluate someone else's 'how' and see if it makes sense - jv
    Last edited by John Vreede; 07-27-2018 at 09:03 PM.

  9. #9
    Senior Member Cooter's Avatar
    Join Date
    Dec 2012
    Crawling up your skirt
    Totally, yes.
    It takes time for someone to think, and type out the whole process or theory. I'm still waiting for my check from

    This is a permanent record of information for a small amount of niche motorcycles and hopefully is a resource in 20+ years... Thanks for adding quality info to it JV

  10. #10
    Senior Member
    Join Date
    May 2016
    Central Soviet state of new jersey.
    Though I haven't read it in It's entirety, I find it very informative and look forward to reading the rest of it.

    Thanks for posting it up.

    P.S. After I first clean off the grounding spots, I use motorcycle roller chain spray on all fasteners and metal spots, it has an anti corrosive in it and I've used it for years for this specific purpose and once applied have never had any connection problems, and no, it's not Seafoam !

    Last edited by njloco; 08-02-2018 at 04:04 PM.

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