74 r90/6 bmw front cover/points water fouling.

Discussion in 'Airheads' started by mfp4073, Jun 6, 2012.

  1. mfp4073

    mfp4073 Long timer

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    Got stranded for an hour tonight. Out in the middle of nowhere, at 1am, in the dark, in the rain. (and uphill both ways :rofl) Anyways, riding along and it starts cutting out. Almost like its out of fuel. Finally dies completely. Check fuel, got fuel. check spark and its intermittent. Took the tank off and started going over stuff. No gain. Went to take off the front timing cover and about a 1/4 cup of water comes out of the timing/points area. Hrm. Try it again, spark it back. Seems as if it got filled and grounded itself out. Got down on hands and knees and dried it as best I could and blew it out. Back together and off I went. Not so bad, only down for about 45 min.

    So here are the questions.

    1. have a cut down fender on the bike, need to change back over to my long fender for the wet season. How much could this be contributing?

    2. what seal is supposed to keep water out of there? There is a partial seal around the distributor and then the condenser wire has a boot/seal. I did have to cut down the top of the rubber boot for the condenser wire to do some wiring. So maybe that is contributing? New condenser would come with new wire I suppose...

    3. how bad would it be to just drill a drain hole in the bottom of the timing cover. I could do it at an angle such that it would drain front to back. If it made things worse I could always tap it and just put a bolt in there.


    So what do yall think? Ever heard of this before?
    #1
  2. mykill

    mykill odd

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    There is an O ring that surrounds the points area as well as the "difficult to seat properly" point wire rubber thing. If all is not perfect then they tend to hold water in better than keeping it out. I have run well for years without the gasket but my bike rarely sat cold in real rain like you get in Florida. Never had an issue in stupid hard rain while riding, I suspect the engine heat helped my cause.
    The drilled hole may be an interesting solution if all else was in proper order.
    #2
  3. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Replace the rubber sealing strip and the rubber points wire tube and make sure that they are sealing well.
    #3
  4. disston

    disston ShadeTreeExpert

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    The front fender is probably not the problem.

    The rubber strip that fits in a groove around 90% of the points area needs to be in good condition. More on this in a moment.

    The rubber boot that the points wire goes thru needs to be in good condition and is hard to position so that it actually works.

    There are two screws that hold the points plate in position. The bottom screw has a question mark washer under it. the points wire needs to be held in position by the question mark washer and go thru the boot to the condenser. The wire is part of the points not the condenser.

    If you have fresh rubber parts and are real careful with assembly of the whole thing you can still get water in the points sometimes. It doesn't often stop us but it can happen to almost anybody. Any hole drilling will not be a benefit.

    Something extra concerning the rubber strip. These were originally two different sizes, different widths. I think there is only one being sold now so half of us have the wrong size rubber strip. I don't know which one is which or which one you have. It's not important. Get rid of the rubber strip. Use a piece of electric wire, stranded copper, about 18 gauge will fit, but you may have to try several till you find one that fits. Put the strip of copper wire, properly trimmed to fit the groove. It will not need to be glued in place like the OEM rubber. It should stand a little proud of the Aluminum of the case so it is compressed by the installation of the front cover. And as a bonus you can use red or green or black wire, any color you like.
    #4
  5. Wirespokes

    Wirespokes Beemerholics Anonymous

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    When installing the Dyna ignition, they recommend drilling a drain hole since any moisture in there can kill the electronics. Prior to my ownership, my 77RS got a Dyna and a drain hole drilled in the case. I'd have drilled it in the cover, but too late for that now. So far it hasn't been a problem and I've ridden in some pretty heavy rain for long periods. A couple months ago I rode to the Bay Area and it rained most of the 600 miles there.

    That said, I've never drilled any drain holes and haven't had a problem with water collecting in the points area. Make sure the seals are in good shape and you should be fine.

    As for the fender - it's probably a good idea running with the full one in the rain. The front tire kicks up a lot of water and blasts it right at that front cover.
    #5
  6. supershaft

    supershaft because I can

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    It is definitely a touchy setup that can be easily messed up every time you take the front cover off and is really pretty tricky to try to guess if you got it back together right when you put it back on. That is until you get into some water.

    Shortened fenders?? Nein Danka! If I wanted fenders that don't work I would get a newer bike! Shortened fenders are for fair weather riders. :D
    #6
  7. mfp4073

    mfp4073 Long timer

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    thanks guys. Good info all round. Looks like some new rubber is in order and maybe a drain hole, still debating.

    And yeah, the short fender looks good. But know its only a dry season unit and why I kept my old full fender! :D
    #7
  8. pkboxer

    pkboxer Been here awhile

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    When I got fed up with the rubber strip "seal" i put a bead of silicone high temp caulk around the rim of the sealing area on the front cover.

    Let it cure completely, then assembled the front cover.

    Next time I took the cover off, the caulk had conformed/deformed to the area on the timing chain cover but stayed with the front cover.

    Has been off/on a few times and still looks in good shape.

    Only did this once so not saying it'll work for anyone else.... :ear
    #8
  9. mfp4073

    mfp4073 Long timer

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    well finally have an end to the story. I replace the condenser wire rubber "tube", figured that would solve the problem. Then another day in the rain and got water in it again. This time I replaced that rubber seal around the distributor housing and then several days later got into 20 miles of heavy downpour. No problems now and no water in there. Not sure what happened to the old one, it looked like it was indented all the way round and had no damage.

    Oh well, another lesson learned!
    #9
  10. chasbmw

    chasbmw Long timer

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    Points shorting out during river crossings was one of the reasons why I switched to a Boyer ignition when I travelled through north and south america on my R80 in the 80s. Fitting the front covers on the earlier bikes is arkward, getting the points and tacho cable seals all seated properly.
    #10
  11. garthg

    garthg Been here awhile

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    The seals were definitely contributing, possibly the whole cause, but you shouldn't have to rely on them so much. They're so easy to get mangled when reinstalling the front cover.
    It's necessary for air to get behind that cover to cool the alternator. (Note the vent on the lower right side, facing the engine).
    Suggest you put the original fender back on. In the heavy splashing/downpour, water may be getting sucked into the cover through the vents.
    #11