Timing cover on Airhead

Discussion in 'Airheads' started by TEXASYETI, Nov 3, 2007.

  1. TEXASYETI

    TEXASYETI Call me "thread killer!"

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    Hey folks,

    Before I get myself into a heap of trouble, I want to get a little advice from the peanut gallery.

    I am working on a r100/7 motor which has been transplanted into my r80g/s. Part of my plan to get the bike ready - cosmetically and mechanically - was to pull off the timing cover, paint it, and check out the timing chain while I am in there.

    At this point, all of the electronics behind the engine cover have been removed - No ignition cannister, rotor, stator coil, diode board, etc. The only thing left is to pull the cover.

    what is the best procedure? My Clymer manual shows a puller being used. Is this really necessary?
    #1
  2. Stagehand

    Stagehand Imperfectionist

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    a puller? :headscratch

    isnt it just a couple of allen bolts and a gasket?

    http://homepage.sunrise.ch/mysunrise/joerg.hau/mot/r80gs.htm#timingchain

    9. Now remove the nuts and bolts that attach the timing cover. There are 9 allen head screws and 3 allen head nuts. On my GS, all bolts have the same length. There will be a few drops of oil leaking out, but not much - you do not need to drain the engine oil.

    10. Breathe, then pull the timing cover straight towards the front wheel. Mine came right off, but if this is not the case you should heat the area around the crank bearing (that's where the "cone" for the rotor comes out) with a hair dryer or hot air gun. There is a bearing which fits snugly into the timing chain cover, which causes the part to "shrink-fit".
    Recover the washers for the 12 fasteners that might still reside in the timing chain cover. Clean the timing chain cover.
    #2
  3. TEXASYETI

    TEXASYETI Call me "thread killer!"

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    Thank you for the info and the link. Great info! :clap
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  4. myblubeemer

    myblubeemer MOA, IBA

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    #4
  5. Country Doc

    Country Doc Wanderer

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    If you've got the cover off, and decide to replace the timing chain, most suggest replacing the crank sprocket at the same time, as they both wear. Unless you've got timing chain noise (skeleton rattle at idle) and/or jumping/irregular timing marks, I'd leave it alone.

    Make sure you don't forget the two little circular washer/gaskets that go between the cover and engine block up near the starter motor, that keeps the top of the timing cover aligned with the bottom 2/3rds that already has a gasket.

    Another thing you might consider doing while you're there is replacing the tacho drive seal, you have to remove the cover to get at it, and you'll curse yourself for not doing it while you're there and the cover is off. Renew the crank and cam seals in the cover as well, they're dead easy to pop out and refit new ones.

    dc
    #5
  6. Mugwest

    Mugwest .

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    do the 3-wire ground harness upgrade before you button all the charge electrics (diode brd, alt etc) back up to the timing cover. It's a factory retrofit PN that is'nt on the fiche (i've never seen it there anyway). Essentially make a 3-wire deal that ties in the left starter mount bolt, the diode board ground and the timing cover (the timing chain cover, not the front engine cover)

    instructs on ibmwr.org or here prolly
    #6
  7. _cy_

    _cy_ Long timer

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    #7
  8. bmwrench

    bmwrench Long timer

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    A puller is almost never needed. If worse comes to worst, you can pull the starter cover and give the timing cover a couple of love taps with a plastic mallet. You might also warm the cover around the bearing housing.

    Make sure you have all the bolts (and nuts) out!
    #8
  9. disston

    disston ShadeTreeExpert

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    It's really common to miss one of the bolts holding the timing cover on. I think the number mentioned is nine (9). I think that is correct.

    Heat around the area where the alternator rotor went. There is a bearing on the nose of the crank shaft that fits sometimes tightly in the timing cover. Mentioned before but worth repeating.

    If you pry with a screw driver between the engine case and the cover you will leave an ugly mark.
    #9
  10. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    As long as we're talking "front cover", what is the lifespan (or critera for replacement) of the front ball-bearing? Mileage? Length of service? Feel? Mine is 25 or 38 years, 90K or 180K miles and second or third timing chain replacement (I don't recall if I replaced that bearing during the "major go-through" in the early 1980's). Sometime in the Spring I'm doing a timing chain and crank sprocket replacement and although the $30 for the bearing isn't a major cost, if they last "forever" I'll spend that money elsewhere...
    #10
  11. coastranger

    coastranger Been here awhile

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    a puller fro the front cover ??????

    now I am not a bmw guru. Ive only rebuilt two bmw engines ( 78 and 85) and I sure did not need a puller to get to the timing chain

    and yes dont forget the two little washer/gaskets at the top. Unless things have changed you have to order them seperate from the front cover gasket so dont assume that since you ordered the gasket you will have those two important washer thingys
    #11
  12. disston

    disston ShadeTreeExpert

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    I've heard a very respected Airhead wrench say he replaces it every time. I've replaced mine when I did a chain. I've done the chain twice but I think I only replaced it once. It had the tiniest bump in it when I felt the action. I think a lot of gear heads try to reuse them.

    A better question might be why is there this bearing there. It sits in the timing cover. Doesn't seem to me this would have much effect on the crank shaft that is held by the front bearing. I wonder how the bike would do if I left it out? Not going to try that. Just wondering.
    #12
  13. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    That front bearing is under minimal axial and radial loads; it is along for the ride. It's purpose is to mitigate any "whipping" of the alternator/crankshaft nose that might occur.

    I probably replaced it back when I did that timing chain in the '80's, but the last timing chain job in 2001 was on a budget-- I didn't even replace the crankshaft sprocket.

    I'll do it right this time...
    #13
  14. wirewrkr

    wirewrkr the thread-killer

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    I've replaced a bunch of timing chains over the years and have torn down 3 times as many more for parts and have only needed to replace that bearing once.
    I had a good selection of excellent used ones, so it was no big deal.
    If it ain't broke don't fix it, I always like to say.
    As far as the original posters dilemma, A timing cover puller???
    Never heard of one, never needed one, and only had to use heat once around the nose bearing to facilitate removal.
    #14