Timing chain clip fail, '81

Discussion in 'Airheads' started by ME 109, Mar 11, 2015.

  1. ME 109

    ME 109 Long timer

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    I got bored with a failed output shaft, so now I'll start an '81 timing chain clip fail thread.

    Here's the clip, with maybe 50,00 k's. What could have made this clip wear to the point of falling off?
    Too much redline? I dunno, it's not difficult to put a clip on a timing chain.
    Anyway the bike, she no go.

    [​IMG]

    [​IMG]

    [​IMG]

    Fortunately this happened in 2nd, below perhaps 2250 rpm, I have considered the prospects of it happening at much higher rpm.
    Fortunately again it appears, there was no contact between valves and piston crowns. I cannot see even a small contact point.
    There is some collateral damage inside the timing chest, however.

    The barrels, heads and lifters are removed.
    Lifters are very good at 275,000 k's, considering the life they have lived. Lots of good full zinc oil. :wink:
    The cam lobes are very clean as well, with a little discoloration? on the low points of two lobes.

    Starting on the parts list............

    Oh yeah, forgot the main attraction.

    [​IMG]
    #1
  2. ccmickelson

    ccmickelson MonoMania Supporter

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    Do you recall if the clip was installed in the right direction, with the open end pointing opposite the direction of chain travel?
    #2
  3. Cogswell

    Cogswell Now living the new normal.

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    From the wear marks on the clip and plate it kind of looks like the sprockets were not in proper alignment. Looks like the master link pin was pulling on the clip with the resultant wear on the plate. :ear


    Mike
    #3
  4. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    There is something wrong with that spring clip, either by design or wear. It should fit and clip securely to BOTH of the link pins, like these examples:

    [​IMG]
    [​IMG]

    I'd suspect a design defect-- I don't see how or why it could have worn like that. IMHO. Seeing that clip, I would have been hesitant to use it, but I've used many clips over the years. If one hadn't done a lot of them, there is nothing that would have set off alarms-- it's a dang clip. Even then, I just examined the master link clip to be used on my upcoming timing chain job and "verified" that it is an acceptable type.

    But, there nothing you did wrong, and high rpms would not have caused this clip to fail. Stuff happens.

    Unless you really want to do a top end job now, you could do it later (like next year, between riding seasons). I would at least break the heads down and visually examine the valve seats and faces for recession and the valve quides for wear. Note how much wear there is, and assess whether you'll need to get back to it in 10, 20 or 30,000 km. A few years back I had two pulled cylinder studs and while the heads were off I looked closely at everything, "decoked" the heads, lapped the valves and got another 20,000 miles out of those valves-- they were wore slap-out when I did do them but hadn't failed.

    All things considered, you came through this incident very well. Really.

    [​IMG]

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    And for your "Dayum!" file, an extreme case of chain failure:

    http://www.bimmerforums.com/forum/showthread.php?1532319-Timing-Chain-Failure

    "Engine has at least 14 bent valves, possible piston/connecting rod damage. Close examination of the chain indicates no other links with signs of wear or ..." supposedly a BMW V-12 car engine:

    [​IMG]


    --Bill




    Yep, something to check:
    #4
  5. Olliew72

    Olliew72 Been here awhile

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    I had the fish clip on my 71 (with duplex pain in the keester chain). I found the clip in the oil while changing it. I'd been riding around for who knows how long with it like that???

    When I took the timing cover off to reassemble it, there was no sign of wear or anything wrong. I went and got a new clip and sealed it all back again.

    That was about 1500 miles ago. I've been tempted to change the oil early, just to see if the new clip is in the oil pan again. Maybe I'm just paranoid...
    #5
  6. ME 109

    ME 109 Long timer

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    Yep, correct direction. This clip has fallen off, rather than been knocked off.
    #6
  7. ME 109

    ME 109 Long timer

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    I noticed the wear marks and wondered what situation could cause it. If it were misalignment I'd expect the other links to show similar symptoms........I might do a chaintopsy.
    #7
  8. Disston

    Disston ShadeTreeExpert

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    Just look at the alignment of the chain sprockets from the side. If they are out of line enough to do damage then it will be visible to the naked eye.
    #8
  9. ME 109

    ME 109 Long timer

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    Charlie, I tested the combustion chamber sealing as you suggested by inverting the heads and filling with fuel.
    Both heads are as tight as a fishes bum. Excellent!
    #9
  10. Disston

    Disston ShadeTreeExpert

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    Good news.

    I don't know if there is anything else you can do for the valves. I have recently investigated doing valve guides at home and I'm sorry to say it doesn't seem to be a Harry Homeowner type job. Even for the World's leading Shadetree. The heads I have now are going to be taken apart tho and the guides measured (I got that far)

    I do have a second pair of heads I may try to do guides on.
    #10
  11. ME 109

    ME 109 Long timer

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    Crank sprocket is off now, but I'll be sure to check the new part installation.

    Looks like it's a matter of sorting out the damage in the timing chest and put it all back together.
    The barrels are really very good considering their mileage, although they could do with a deglaze to reveal the cross hatching.
    I'll have to read up on that again. Someone mentioned using a scotch pad with whatever fluid, with good results, iirc.
    #11
  12. BMurr

    BMurr Been here awhile

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    The link remaining on end of chain which is pointing downwards on left of picture appears to my eye to have a hole which is rather large when compared to its opposite member on the upward pointing end of the chain, as if it was worn out by the link flopping about. Is it possible that the link was too long, such that each time it comes off a sprocket it gets a shock as the slack is taken back up, the repeated shocks eventually breaking it down?
    #12
  13. ME 109

    ME 109 Long timer

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    I think the hole is larger because the roller has fallen out from its position between the two side plates.
    I'll have a closer look when I get home, but I think the roller has a reduced section on either end that fits into that hole.
    #13
  14. chollo9

    chollo9 Screwed the Pooch

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    First, it went 50K, so that makes it really hard to say what the cause was. If it let loose early on, I'd lean toward possible over-spreading of the spring clip or something like that. Correctly installed drive chain master links fail without apparent reason, hence the lack of reliance on them for high-mileage type folks.

    Unfortunately, many failures occur without our knowledge of cause. All we can do is take every precaution possible upon assembly and hope for the best.
    #14
  15. ME 109

    ME 109 Long timer

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    The wear patterns on the joining link suggest that the chain was being bowing outwards. A crank sprocket that was not fully seated would cause such a bow. I guess mine was fully seated? Prolly can't get the timing cover back on if the sprocket isn't fully seated.
    I did a chain break close to the joining link and found no such similar wear.
    The clip for the link is a thin little bastard, I measured its thickness at approx halfway along its length where there was no significant wear and got .7mm
    The clip is also bowed across the closed end, that is the clip does not lay flat.

    Anyway, the rods are staying put and the cam is staying put.
    I'm thinking of deglazing the barrels as I mentioned, but that should only be done with a new set of rings?
    I haven't looked at the price of rings, and the bike doesn't blow any oil smoke or lack power.
    What says popular opinion?
    #15
  16. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Good point and something that hasn't crossed my mind in years. I've gotten so accustomed to cutting the original chain off and using a master-linked chain when doing a timing chain replacement that I didn't think of the stock "endless" chain. And by eliminating the master link you eliminate one possible "weak link" in the system. Of course you'd need to pull the transmission and pop the oil pump cover to do that, but that's not a big deal.

    Something to consider, ME109...

    --Bill
    #16
  17. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    When the sprockets are installed put a straight edge across the cam sprocket and see how it lines up with the crank sprocket. The sprockets pretty much fall into place when installed. The crank sprocket especially since the nose bearing has to fit and seat down for the timing cover to fit. The cam sprocket is a press-fit on the shaft (along with a key) and the camshaft axial play with the cam bearing assy has to be adjusted by carefully pressing the sprocket to or fro. That cam sprocket is THE prime candidate for misalignment. Is the camshaft stock, or otherwise notable?

    --Bill
    #17
  18. chollo9

    chollo9 Screwed the Pooch

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    Agreed on the crank sprocket, but the cam sprocket can be set fore and aft a bit. Maybe that's where the issue lies?
    #18
  19. boxerboy81

    boxerboy81 Stay Horizontal

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    Grant paid $120 or so recently for his new set of rings for a nikasel motor.
    Motorworks.co.uk have them for around OZ$40 a set-$80 plus post.

    Munich @ $70 a set-$140 plus post.
    #19
  20. Jim Day

    Jim Day full manic mechanic

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    Sorry to hear this.

    I think that clip is excessively worn but I also think it's clip from a Japanese bike. The reason it's worn is because it's a link for a longer chain link, and though it was locked in right at the open end but was sitting too far back at the closed end. That allowed some play and it was moving back and forth.
    #20