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Thread: Pushrod Centered in Tube

  1. #1
    GTDOUG
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    Pushrod Centered in Tube

    This maybe a silly question but I noticed on my R100RT that the exhaust pushrods are not centered in the pushrod tube when the exhaust valve is fully closed. The pushrods are so close they maybe rubing on the pushrod tubes. This of course changes when the motor is rotated when the exhaust valves are opening. In reviewing Clymers manual nothing is metion about this.
    GTDoug

  2. #2
    Registered User PeoriaMac's Avatar
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    Did you checvk last month's "Keep 'Em Flying" column in the BMWMOA News? This was addressed to a degree. The short answers are: "Yes it can happen" and "Do you own a dremel?".
    Mac
    1986 R80RT, 2005 R1200GS
    Livin' Large On The Lake

  3. #3
    Registered User beemerguru's Avatar
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    Has the head been milled due to warping sometime in the past? That will also change the geometry.

    What year RT? Later models had the updated rocker arms and needed the big fat washers under them. If someone retrofitted late model to an early model head, might cause some geometry issues.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  4. #4
    GTDOUG
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    Sorry about the lack of information... It's a 1982 R100RT. The heads have been milled. I will check last months MOA issue.

    Greg: Of course this is a later model, to my knowledge an earlier model head was not fitted to this motor. Everything I have read and looked up leads me to believe these are the orignal heads that have been milled, to my knowledge, only once. There is however 79K on the bike, so it is possible they have been milled more than once. I am still in contact with the previous owner and he does not think the heads were milled under his watch.

    MAC: I hope your not serious about the dremel.
    Gentlemen, Thank you for your help.
    GT Doug
    83' R100RT
    07' K1200GT

  5. #5
    GTDOUG
    Guest
    MAC: Thank you for your imput. The local BMW shop agrees that a little triming with a dremel on the pushrod is in order. I always get nervous when removing metal from a critical part.
    GTDoug

  6. #6
    Unregistered User dduelin's Avatar
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    I would look at the pushrods and see if they are rubbing. They might look like they are rubbing and they are not. It is normal that they are not centered for a full rotation of the camshaft. Sometimes a head gasket is installed backwards and this may cause the pushrod to rub on the gasket as it is not lined up properly with the pushrod tubes. The pushrod rotates when in use. The shop recommends trimming the pushrod down in diameter? They know they are hollow, right?
    Dave
    R100
    ST1300

  7. #7
    Registered User beemerguru's Avatar
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    If the heads have been milled, you need to add 4 washers to bring the arms back up to get the geometry right...or the pushrods will rub

    Check in the Book to see what the factory head deck heigth should be and find the difference to yours..that's the size of the 4 washers.

    Dave is right that a backwards head gasket will cause rubbing...but the milling is more likely the root cause.
    Greg Hutchinson
    R80G/S (4) 633CSi with 450K mile
    '68 R60/2 '88 K100RS Special Edition
    http://gregsgssite.shutterfly.com/

  8. #8
    GTDOUG
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    Greg and Dave,
    Thanks for the timely responce. I am looking into the washer cure. I did not feel comfortable griding on a hollow tube. I pays to take your time on these kind of projects.
    GTDoug

  9. #9
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    The airhead article is about CAREFULLY milling a tiny amount from the end/inside edge of the pushrod TUBE, NOT the pushrod itself! This is after examination that the pushrod was being worn down by contact with the sharp inside edge on the end of the pushrod tube.
    BMWs in my garage: 1982 R65LS, 1978 R100/7

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