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Thread: R100/7 Electrical starting issue - any advice?

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  1. #1

    Question R100/7 Electrical starting issue - any advice?

    I am very well trained in mechanics, but I also dread any electrical/electronic issues.

    I used to own 2 BMW's years ago, a 1968/2 500cc & a 1975/6 900cc. Rebuilt both engines (just top end on 900) and both ran great. I sold them both about 20 years ago when I had several small children - didn't want them to grow up without a dad. they are all grown up, and the last one, the only one with any mechanical ability just purchased a used K100, so I decided to purchase another boxer.

    I recently purchased, but have not ridden yet, a 1978 R100/7. It is cold here in Ohio, but when I tried to start it, it turned over but it wouldn't start, but it did a lot of "clicking" similar to when a battery is low. From the previous owner, he said the clicking was there (he told me before I purchased) but that it didn't affect the starting. Once the engine turned over, it started.

    However, the clicking bothers me. Is it just the battery? It has a "Battery minder" on it and presumably working - I've had it plugged in now for 3 days. Should I purchase a small charger and try that first?

    Is it the solenoid? And even if not, how hard is it to rebuild one of those? Finally, could it be worth the time now (as I won't be riding for the next few months during winter) to go ahead and pull the starter motor and solenoid and rebuild them both?

    Any pointers, instructions, videos that you might know of to help?

    BTW, there are no really reliable "old-school" BMW dealers nearby to get good advice!

    I recently re-joined the BMWMOA last week just to keep up. Now, that my kids are all grown up, and I have one who also has a BMW, I hope to do some enjoyment riding and maybe even make some of the BMW meets. I love the Civil War history (Southern perspective) and may try hard to make the Gettysburg meet in April.

    Just an FYI, the previous owner told me the clicking has been around for some time, but he was never bothered by it, because the bike always started.

    Thanks ahead of time for any help you might give.

    Jim C. - Be sure to put "BMW" in the subject line as I never open emails when I don't know their source.

  2. #2
    Registered User mneblett's Avatar
    Join Date
    Nov 2005
    Fairfax, VA
    Three possibilities come to mind, assuming the "clicking" is a relay-sounding click, and not a heavy mechanical click like the starter nose gear bouncing off the flywheel due to the starter solenoid's failing:

    Dying battery (load test: measure voltage when starter is engaged -- if voltage drops below 10V during cranking, replace)

    Dying starter relay (easier to replace than trying to troubleshoot)

    Corrosion at the spade connections in the plug beneath the starter relay (not uncommon -- this area sees road spray).

    While it could be the starter, the old heavy Bosch starters are built like tank armor, and are generally reliable (both the Bendix and the solenoid). Unless the clicking noise is a heavy metal-on-metal noise, the starter would be one of the later things to check.

    ps - one way to check for the source of the click is to pull the tank, and put your finger on the starter relay shell to see whether you feel the vibration from the coil pull-in bouncing. If you feel no vibration, you can pull the starter cover and put your finger on the solenoid body to see whether the clicking is there.
    Mark Neblett
    Fairfax, VA

  3. #3
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    99% of the time it's the battery.

    I might be inclined to reduce this to 95% as these bikes are getting older and older.

    Remember that anytime a non-direct fuel injected engine is started cold it needs both extra fuel and extra air. On Airheads there's no fast idle cam and obviously no idle control valve so the extra air comes from your hand opening the throttle a bit. Serendipitously, opening the throttle a bit decreases engine vacuum and makes the starter's job easier.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  4. #4
    My son & I share a 95 R100RT that had some similar starting problems.
    The problem was intermittent.
    There would be a clicking, the engine turned over as if it had a weak battery .
    It sounded and acted like but was not a dead battery.
    It was the starter relay that worked some of the time but not all of the time.
    It was easy to replace, not costly and solved the problem.


  5. #5
    Minnesota Nice! braddog's Avatar
    Join Date
    Jun 2003
    Twin Cities - MN
    Once the engine turned over, it started.
    This says a lot. My '77 R100RS has always been the same way, meaning, if the engine will turn over at all, it will start.

    Check the voltages of the resting battery and the battery under load. Any idea how old the battery is?

    Check all of your electrical connections, they can get corroded. This includes connections to the starter relay. Shine them up, lube with some dielectric lube.

    Good Luck, Welcome Back, and be sure to let us know what you find!
    Brad D. - Member #105766
    '77 R100RS - Black Beauty (big pipe, baby!)
    '94 R1100RS - Sylvia

  6. #6
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Pismo Beach, CA
    Welcome back to the fold Jimmy Lee.

    So much of an airhead's electrical "performance" hinges on a sound battery. If you don't actually know how old the battery is, you'd be ahead to replace it outright, IMO. The /5 models had a fatal flaw built into their starter relay/ protection circuit that imitated the sound of a low battery charge (the clickety sound is know as "the cricket") but that issue went away with the /6. That isn't to say that your starter relay might not be at fault.

    BTW, this is a great book if you enjoy reading about the southern perspective of the WBS. If you enjoy reading naval history it's a win-win.

    Memoirs of Service Afloat During the War Between the States

    by Admiral Raphael Semmes, CSN, 1869.
    Captain of the CSS Alabama.
    The Blue & Grey Press
    ISBN: 1-55521-177-1

    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  7. #7
    Monza Blue 1974 R90/6
    Join Date
    Dec 2006
    I don't see how you can go wrong replacing the battery (except that it will cost a hundred bucks or so). Reason I say this is that it might already be close to its 4-5 year life, so you'll be needing to replace it fairly soon anyway. And, a dodgy battery causes so many strange electrical problems that it will have you chasing symptoms all over the bike. Lots of good feedback about the new, physically smaller, but better batteries. Odyssey is one brand. Nice thing is that you can install or remove them without having to remove the carbs and air filter or separating the frame (although you will have to do it one more time to get the old one out).

    Next step is to clean up the wire connections on the starter relay (especially the red one). If that (and the new battery) doesn't solve the problem, a new relay from Motorrad Elektrik is $10. Like the above post noted, easier to spend the $10 and replce than to try and troubleshoot/repair the starter relay. (half way down the page).


  8. #8
    OK, Where's the best place to purchase a battery? WalMart?

    Any suggested brand better than any other?

    Any local MC shop - closest BMW shop is 30 Miles away!

    Jim C.

  9. #9
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    For sure not WalMart.

    You do NOT want a battery that vents through the cell caps but rather has a connection for a vent hose.

    That is unless you can find an AGM.

    I'd drive the 30 miles.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

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