Rocker Arm Shim

Discussion in 'Airheads' started by some_guy, Oct 10, 2012.

  1. some_guy

    some_guy Been here awhile

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    So I did a valve adjustment last weekend on my 95 R100RT and noticed that one of my rocker arms had some vertical play. If I remember right this is probably what is causing that head to be noisy and could potentially trash the rocker arms or worse if the needle bearings come apart...anyone have any experience with this? How long can I ignore it? There were 2 shims already in place (part 11 below). Do you add shims or try to keep the number of shims low?

    [​IMG]

    Thanks!
    #1
  2. JonnyCash

    JonnyCash turd polisher

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    They're available in different thicknesses, so instead of adding to the total number, you could just get thicker ones. That said, I cant see why it would really matter how you make up the thickness, but I would personally go for the least number of shims necessary to get end float where you want it.
    #2
  3. supershaft

    supershaft because I can

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    The needle bearing cages still break with no play there. I think it helps to have zero play but I know for sure that it doesn't stop needle bearing cages from breaking. You can adjust the play out exactly like you do on the earlier setups. You don't need any shims. I have adjusted them by squeezing in the blocks hundreds of times as have a number of other mechanics I know with no problems whatsoever. Besides, the shims don't come in enough sizes to get the end play as perfect as I like to get them. I use a modified Vise Grip C clamp. IMO it is THE best way to get the adjustment down to a gnat's ass.
    #3
  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I tried that approach using a C clamp. However it loosened back up and added a shim instead.
    #4
  5. supershaft

    supershaft because I can

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    Anything is possible. I don't know how sometimes but . . . .
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  6. Boxer Metal

    Boxer Metal Mad Scientist

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    A "C" clamp does not work with the late style rocker arms as the end blocks are located into the head and there is no movement. Stick a feeler gauge between the rocker block and rocker arm to figure out how much play you have. Take that number plus the thickness of the shims that are already there to figure out what combination of shims you need. I agree- the fewer the better/easier
    #6
  7. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    ^^^ yep, what Chris sez ^^^
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  8. 100RT

    100RT Long timer

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    I believe the shims come in about 5 different sizes.
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  9. Boxer Metal

    Boxer Metal Mad Scientist

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    You are correct
    0.20mm
    0.25mm
    0.30mm
    0.35mm
    0.50mm

    I noticed the price on the 0.35 is over 3.00 while the rest are 73 cents. Buy 73 cent ones now before BMW raises the price to $3.57. This will happen when they have to reorder them from BMW AG.
    #9
  10. naginalf

    naginalf Handy Schtroumpf

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    Is'nt that .20mm, .30mm, etc.?
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  11. Boxer Metal

    Boxer Metal Mad Scientist

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    You are correct.
    #11
  12. some_guy

    some_guy Been here awhile

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    Yup. Gonna order some today.
    #12
  13. Stagehand

    Stagehand Imperfectionist

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    THey've been priced that way for over a year. I did this like, january before last and was like wtf, lol $3.75?
    #13
  14. adventure950

    adventure950 Anglo-Saxon

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    #14
  15. supershaft

    supershaft because I can

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    Well, I guess all these years I have been dreaming. No, not really. A C clamp DOES work with the late model setup. It works better than shimming them. I have worked with quite a few that adjust them the old school way. It's easier, faster, cheaper, and better. The 'better' part sells me. Go ahead and shim them if you want, I am just trying to help some do a better job.

    That MI setup looks like a solution to a problem that doesn't exist. One thing I have noticed in life: Problems are easy to fix when you make them up to start with.
    #15
  16. Jay.T

    Jay.T Adventurer

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    It does work on late model airheads. I had to first take up as much space as I could with the shims and then clamp the rest out. My rockers now sound smooth.

    About a year ago someone told me to clamp them, but I though they were getting the different models years and adjusting techniques mixed up. After the clamping technique and late model airheads came up earlier this summer on this site, I tried it. I figured now I heard it twice. A couple thousand miles and they still sound smooth.
    #16
  17. woodly1069

    woodly1069 Long timer

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    Hate to stray off topic, I know the bike in question is much newer than my 1973 airhead but do they all have needle bearings under the rockers? My right head is much more noisy than the left and I have tried clamping with no success. Now wondering if I have needle bearings. Current microfiche don't show a part number...thanks!
    #17
  18. Airhead Wrangler

    Airhead Wrangler Long timer

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    If they're original then no, you don't have needle bearings in those, just bronze bushings up through '73. They are upgradable to the /6 type with needle bearings if they are in fact hosed... and they often are.
    #18
  19. some_guy

    some_guy Been here awhile

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    http://bavarianmotorcycleworkshop.com/tech-articles/valve-adjustment-seminar-bmw-air-head-engines-1970-onward


    Style #1 The very early /5 models had rocker arms that were pivoted on a bushing. This style of rocker arm was narrow vertically and had a spacer on the pivot shaft about the same height as the rocker itself. They were prone to early wear so most of them have been updated to one of the newer styles described below. If you still have a BMW with this style rocker it would be a good idea to remove the rocker arms one at a time and check for wear in the bushing and the pivot shaft. If wear is evident, it would be best to update the rocker arms to a more modern style.

    Style #2
    The later /5s and /6 models had full length rocker arms that filled the whole space between the RAPB’s. These were pivoted on caged needle bearings, two (or a pair) per rocker arm. On this and the above mentioned Style #1 rocker arm sets, the RAPB’s were not indexed to the head. The RAPB’s simply sat on a tube that the 10mm studs went through and had enough slop in them to adjust the position of the RAPB’s. This is where being a mechanic becomes very important! Not only does the vertical clearance need to be set (as described below) but the entire shaft + RAPB’s + rocker arm + pushrod assembly must be set exactly square on the head and positioned so that the pushrod does not hit the inside of the pushrod tube as the valve opens and closes.

    Style #3
    The /7 through 1984 models had full length rocker arms that were pivoted on a pair of caged needle bearings per rocker arm. These had RAPB’s that fit loosely over a bushing that was pressed into the head and went around the 10mm studs. On this style rocker, the vertical clearance still needs to be adjusted, but there is no need to be concerned about the pushrod hitting the inside of the pushrod tube.

    Style #4
    Found on 1985 and through end of production for air heads, this was the most advanced and best of the rocker arm systems. The rocker was pivoted on two caged needle bearings per shaft. They incorporated a plastic noise dampening bushing into the rocker arm. The RAPB’s were precisely indexed into the head and the vertical clearance is set with shims that are available in various thicknesses. Once this style of rocker was run in and properly set, it was very unusual to ever have to reset the vertical clearance; and, there was never a concern for the pushrod ever touching the inside of the pushrod tube.
    #19
  20. woodly1069

    woodly1069 Long timer

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    Thanks to the both of you for the very informative info! My only question is, what is a RAPB's? Mine look like this:
    [​IMG]
    Don't mind the missing intake valve spring there, it was replaced!
    #20