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Thread: Condensers dying premature deaths.....

  1. #1
    On the Road
    Join Date
    Apr 2011

    Condensers dying premature deaths.....

    1977 R100S, still has points and condenser (and I'd like to keep it stock...)
    But the condenser keeps dying it seems....

    It happened at the beginning of the summer- went thru the entire bike- valves checked, timing checked, carbs disassembled and cleaned numerous times, carbs balanced, points gap adjusted, new coils, new plugs.... last thing was swapping out the condenser and it roared back to life.

    Well a couple of weeks ago, it happened again- felt like it had bad gas, back-firing thru the pipes, thru the carbs, VERY difficult to start... etc...
    So I swapped out another condenser.. (3rd in two years! 2nd in a month!!) And immediatly the bike roared to life. To double check, I plugged the older condenser back in and the bike wouldnt' start.. swapped back in the new one, ROAR!

    So I drive 30 miles, and the bike rides like a champ! Then by mile 35, sputtering, backfiring.. same old, same old.....
    So I parked it and left it to this am- thinking that perhaps it was heat getting to something... nope, hard as hell to start this am and wouldn't idle....

    So my question is-- is there something amiss in the bike electrically (or otherwise..) that could be killing the condensers???????
    Or perhaps something else going on???

  2. #2
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    I checked with one of the electrical techs here at work...he said that over voltage and/or heat would be killers for condensors. The condensor sees the 12v coming into the comes in on the single wire...the case of the condensor is connected to ground. Double check that the condensor is well grounded.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Pismo Beach, CA
    and, it could just be "the luck of the Irish" or... the French, or.. .

    Duane Ausherman points out (no pun intended) that, in his experience, condensers actually don't need to be changed with every set of points, and that failure of a new condenser usually occurs within a couple of hours of installation.

    Go ahead and follow Kurts advice but you may have just run into a couple of bad parts.
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  4. #4
    On the Road
    Join Date
    Apr 2011
    Thanks for the info Kurt...
    Not sure how it could be getting too hot perched in the front of the engine....
    I'll check to make sure the post it bolts to isn't letting it ground...

    And lMO-- this is the second condenser I've gone through this summer... not even the irish are that lucky I'd imagine.

    Here's another tidbit- when the condenser dies and the bike starts backfiring etc-
    It's always only the left cylinder that's acting up... the right one seems fine.
    I've swapped plug leads, coils etc... but it's always the left side.
    Pop in a new condenser, and all's well.... any ideas what could be causing it to do that???

  5. #5
    Registered User krpntr's Avatar
    Join Date
    Jan 2010
    Mt Vernon WA
    Are the coils connected properly? The jumper wire can be on the wrong terminal? Sounds like a problem I experienced when I first bought my bike. The coils are connected + to -- . Mine were connected parallel and the symptoms were the same; hard starting, bad idle, backfiring.. . Burned points and condenser. I have the points in a can retrofired to my '82 R100 due to the electronic failure brought on by the P.O.'s error. But nobody caught on to it till I had a VW mechanic look at it. He gave me a set of Blue Dot six volt VW coils and a fresh set of VW points with a new, longer. pig-tail and a fresh condenser. I was back on the road. That was 1998 and the same components are still on the bike. Oh, and he also fixed me up with a larger ground cable. Now, the starter spins with gusto and the bike instantly starts (provided I can get fuel in the chamber).

  6. #6
    There must be a condenser virus going around.. I recently had one crap out on my R90, and my brother had one crap out on his lawn mower. Haha.

  7. #7
    Registered User
    Join Date
    Jan 2006
    New Hampshire, USA
    It is possible that you've just gotten 'lucky' with a few bad parts - this happens increasingly often with more of these old electric parts being sourced from China.
    Or, it may well be a questionable wiring connection, particularly ground. I would check the coil connections, as well as the resistance of the primary side of each coil - you might possibly have one that is starting to go, and this might cause increased stress/voltage spikes on the condensor. You don't have any points amplifier connected do you? Are you using the dual 6V coils, or have you switched to a dual output 12V coil (DYNA)??
    BMWs in my garage: 1982 R65LS, 1978 R100/7

  8. #8
    Check in with Motorad Electric.

    GREAT source, knowledgeable and very reasonable.

    There is some item out there from DYNA (I don't own it as I don't use points and condenser) that is supposed to help the points and condenser. Talk to Motorad.

  9. #9
    Unfunded content provider tommcgee's Avatar
    Join Date
    Dec 2006
    Braintree, MA
    Could just be old stock, capacitors don't have an infinite shelf life.
    Salty Fog Rally 2007, 2009, 2011, 2012, 2014 And DRAT! Missed the last one in 2015!

    -Tom (KA1TOX)

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