Thump From Drive Train

Discussion in 'Parallel Universe' started by Emmbeedee, Dec 3, 2012.

  1. Emmbeedee

    Emmbeedee Procrastinators

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    I had originally thought my wheel bearings were bad, so I replaced them though they looked ok, but the noise persisted. So I figured the cush drive rubbers were shot after 80,000 kms but had not yet replaced them. But tonight I had this idea of putting the bike in gear and trying to turn the rear wheel to see if there was a visible amount of play in the hub when lo and behold, the noise came out of the front of the drive chain.

    So it turns out the front sprocket was loose!

    This was last replaced at about 38,000 by the dealer under the factory chain/sprocket recall.

    The front sprocket is hooked now and does need replacement, as does the chain and rear sprocket, of course. But now I know what the cause of the noise is.
    #1
  2. runnin4melife

    runnin4melife Been here awhile

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    That is some seriously promising longevity! :evil Glad you figured it out. Now if I could only figure out why every time I take a motorcycle apart I wind up with extra bolts?!?!?
    #2
  3. Emmbeedee

    Emmbeedee Procrastinators

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    Probably your so called buddies throwing a few extras into the pile. :lol3
    #3
  4. mapuda

    mapuda Crash Tested

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    Isn't there a locking tab on the front sprocket? It has been awhile since I last changed out my chain & sprocket but most bikes have the tab to keep the counter shaft sprocket from getting loose.

    Figure that the dealer would give the chain replacement warranty work to the noob mech.

    I had replaced my chain about 10k miles before the recall with a DID Xring.
    #4
  5. Reaver

    Reaver Outta Here

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    Wise Guy eh? Why I otta! I replaced a butt load of chain/sprockets under warranty as a n00b. Low tech really. The bolt on the sprocket is like a cymbal, called a Belleville washer in aviation anyway. Wikipedia The singles use a bend over lock tab.

    So not to blame anyone, over 40k kms without checking the bolt for tightness?? :huh For shame! Sprocket hooked? Oops, forgot to look! :eek1 Must've been "Procrashtinating!"
    #5
  6. kelsow

    kelsow Long timer

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    Glad to hear you found out your problem.

    Ever since I owned a drz400, I have been putting locktite on the front sprocket splines.
    It's a bit of a biotch to get off but not a huge job in return for piece of mind.

    I usually ride with the plastic cover removed to keep an eye on the sprocket.
    #6
  7. Emmbeedee

    Emmbeedee Procrastinators

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    Good idea putting Loctite on there. That's what I plan to do. I have some Bearing Mount 620 I hope will be appropriate for the job.
    #7
  8. Emmbeedee

    Emmbeedee Procrastinators

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    Why would I check the bolt for tightness? If they'd done the job right, using Loctite to hold the bolt in, would I reasonably expect it to need checking? If it was Loctited properly, checking it would break the bond anyway.

    We normally get 40,000 out of sprockets and chains, but they're usually hooked slightly by the end of life. I plan to get a little more out of this one though since it's not badly hooked.
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  9. JRWooden

    JRWooden Long timer

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    Rev. #4 of the BMW manual (they are now up to at least rev. #6 but I don't have it... )
    calls for locktite #243 on the front sprocket bolt, with torque of 50Nm

    On rear sprocket it says to use new nuts (they are some sort of special mechanical locking nuts),
    and are to be TTA (Torqued to Angle) 10Nm seating torque, TTA of90 degrees.

    But again my manual is potentially down-level ...
    You'd think that for $120 I'd get free updates but nooooooooooooo :cry
    #9
  10. Emmbeedee

    Emmbeedee Procrastinators

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    Thanks for the torque figures. Saves me looking them up.




    Sent using strings and tin cans and Tapatalk
    #10
  11. Emmbeedee

    Emmbeedee Procrastinators

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    Strange - I was looking at the sprocket today and it almost looks like it has a brass core or something like that.

    [​IMG]
    #11
  12. Reaver

    Reaver Outta Here

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    So does my rev 6???

    Emmbeedee, I am not offended nor am trying to offend. All trades have shoddy workers so that is a possibility as well. My point was that ALL your nuts and bolts should be checked at least once a year or more if required. We don't have the safety factor a car does. If there was loctite on the bolt, and torqued correctly to 50 NM, the loctite would require what, maybe 100 NM of force to break? Therefore checking a tight, loctited bolt would not cause it to move unless it was already loose. The copper you see on the sprocket is copper anti-seize. The reason your sprocket was able to be removed after 40k kms, not rusted on solid.

    The Bulletin on the chain recall was very specific. Both sprockets and chain, lower shock bolt, rear sprocket bolts and swing arm nut were all replaced. BMW doesn't re-use mechanically locking fasteners (or micro encapsulated) on critical components. The lock washer on the front sprocket bolt IS re-used and the bolt isn't loc-tited. The bolt is anti-seized tho, despite what the maintenance CD's say. I can't explain it. I do know that some front bolts and sprockets could not be removed due to rust. Heating the shaft destroys the seals etc so better it be anti-seized with a tq check now and then. One of the failings of BMW is their paperwork and manuals. Sometimes a person would give up trying to correct conflicting information or just simply find a spec.

    Bad flasbacks! :splat
    #12
  13. runnin4melife

    runnin4melife Been here awhile

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    perhaps my days of racing have stuck with me but I safety wire this piece still...
    #13
  14. JRWooden

    JRWooden Long timer

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    Reaver:

    The bolt holding in the front sprocket was to be anti-seized?

    In Rev #4 of manual it says the rear sprocket NUTS that could not be re-used, but did not mention that the bolts were single-use ... implying that re-using the bolts was OK. I realize it is a TTA fastener so .... yeah I'm confused as usual

    And yeah, now the Germans owe me a case of beer damit.... :deal
    #14
  15. Reaver

    Reaver Outta Here

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    As an Aircraft Mech, I can safety wire anything in 2 minutes. 3 if I'm upside down in the dark. Making holes in non aircraft hardware is a little trickier.

    Guess who got to lockwire the Boss's race bikes? :D
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  16. Reaver

    Reaver Outta Here

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    Ok, let's see here. All the bolt on the front sprocket does is to stop the sprocket from falling off. The splines transfer the torque. A circlip would probably work as well. Sure we could get all engineery about it but that's the basic function. Leave the bolt out and limp home. Probably why it wasn't replaced like the rest.

    BMW went sledge hammer to kill the fly that was the breaking chain. You can re-use the rear sprocket bolts if you inspect them first. Replacing the lock nut is probably a Lawyer/marketing tactic. You buy new parts, BMW makes a profit and pays less insurance. In reality, if the nut cannot be installed by hand, then it has sufficient locking ability to be re-used. This hardware set up is under shear force and in a failure situation, could result in wheel lockup. Imagine if the swingarm nut fell off and the bolt worked it's way out. :eek1 The lower shock bolt.....:eek1:eek1 The upper shock bolt uses a curve design to prevent it from coming out. :lol3

    There are two types of maintenance. Breakdown maintenance and preventative maintenance. The difference is location. One you do on the side of the highway at night in the rain (Murphy), one you do in your garage with a radio and a few beer on the weekend. To each his own. I'll continue to anti-seize my bolt and spend 30 seconds twice a year to check torque it rather than lock the shit out of it and hope I sell the bike before I need to remove it.


    YMMV :hide
    #16
  17. Kiwi Tinkerer

    Kiwi Tinkerer Ross

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    I mark the bolt with a little orange paint. (Touch up for my bright orange car)
    I also mark sprocket bolts, axle clamps, axle bolts and fork clamps.

    Then check them before a long ride.

    I am not actually any good at checking but this post has reminded me to do so tomorrow before my next ride.
    #17
  18. JRWooden

    JRWooden Long timer

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    Thanks Reaver - understood, and I agree.

    Like Kiwi I have all of my critical fasteners (that are visible) marked with a black sharpie for a quick-walk-around.
    The sharpie seems to last well, and a quick wipe with carb cleaner erases it when I take it down for maint.

    Kiwi: I'd add the caliper mounting bolts to your list!
    #18
  19. MikeMike

    MikeMike Long timer

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    I would add anything a dealer has touched to the list.
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  20. Reaver

    Reaver Outta Here

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    The three screws that hold the plastic front sprocket guard on are always loose. The bottom one is often missing. Side stand pivot bolt - another forgotten tq check item that's always loose.

    Just spent two hours going over our new-to-us 658 with 20K kms on it. I would guess no one's looked at it too hard even with full Dealer only service history. Many undertorqued things found like handlebars, triple clamp bolts etc. Wheels overtorqued and chain too tight. All part of the Zen of motorcycle maintenance. Besides, it's "Her" bike. :raabia
    #20