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Thread: /7 pushrod tube replacement

  1. #1

    /7 pushrod tube replacement

    I know this has probably been covered here many times but I am new here so Please bear with me.
    I have a 1978 R100/7 that I am in the process of resealing the cylinders and replacing the pushrod tubes.
    I am replacing the pushrod tubes because they leak badly from both the seals and the joint where they join the cylinder, The sealing flanges on at least two tubes are loose to the point where I can move them with my fingers.
    My motor has NO groove on the cylinder for the big O ring and when I took it apart I noticed NO base gasket. Is this normal or am I missing something?
    I have been trying to research just how far to install the new pushrod tubes into the cylinder but I am finding differing opinions. The answers I am finding range from flush with the base of the cylinder to 5mm from the base of the cylinder?
    Also Do I need a base gasket or just some good cement/sealer at the cylinder base.
    Permatex has a product called Right stuff that I have used before to seal aluminium transmission cases and it works great. Has anyone tried this at the cylinder base?
    I understand that bmw airheads are prone to leak oil at the pushrod tubes and cylinder bases so this fix has been done a lot. I am hoping to tap into the wealth of knowledge that exists on this forum.
    Thank you one and all for any replies I might receive.
    David Legg

  2. #2
    Liaison 20774's Avatar
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    I did a top end on my '78 R100/7 3-4 years ago. I'm on my phone now and can't find it. Will add more later.

    Update...here's my thread on the top end for my bike...I did more than just the pushrod tube seals:

    https://forums.bmwmoa.org/showthread...opend-Overhaul

    My bike is a Sept 1977 build. No base o-ring, no groove, no base gasket. There are of course the small o-rings on the upper studs.

    I used Permatex Ultra Grey as a thin layer for the base of the cylinder...I believe I applied it on the engine side, avoid an excess of sealant around the upper studs.

    Here's a post which shows where the collars need to be on installation:

    https://forums.bmwmoa.org/showthread...l=1#post682593

    Note that you will need to refix the collars onto the tube...they must not move around otherwise you'll not get the right pressure on the seals. If they're loose, maybe you can find a shop that can braze them into place.

    Snowbum is a great resource...I've also run across this website for pushrod tube seal replacements...some differences to your bike:

    http://www.pbase.com/dqmohan/prtseals
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  3. #3
    The base gasket was not really a base gasket, but rather a shim to reduce compression on some earlier models to use them with lower octane gas. They came only with a slight smear of sealant from the factory regardless of whether the cylinder used a large o-ring. Oak's top end manual is the premier reference, but it may be hard to find one now. Here is a voluminous reference from Snowbum, which you may have likely seen. It can take some effort to digest, but the right warnings are there and some specific information on tube replacement (which I have not personally done).

    http://bmwmotorcycletech.info/pushrodseals.htm
    Lee A. Dickinson - Danielsville, GA USA
    MOA 80364 | RA 29650 | ABC 3480 | IBA 8914
    1992 R100RS - 1993 K1100RS - 2013 R1200GS

  4. #4
    I have oaks manual and have emailed him questions but gotten no reply. I hope he is still with us.
    Thanks for the info, Parts are on their way from California.

  5. #5
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Quote Originally Posted by davelegg@att.net View Post
    I have oaks manual and have emailed him questions but gotten no reply. I hope he is still with us.
    Thanks for the info, Parts are on their way from California.
    Unfortunately not-

    https://forums.bmwmoa.org/showthread...f-Oak-Okleshen

    OM
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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    2009 F800GS 1994 TW200

  6. #6
    So sorry to hear of his passing, I talked to him briefly on the phone a couple of years ago and was greatly impressed with his kindness and patience for people of limited knowledge. He will be missed by us all.

  7. #7
    I made a drift today on the lathe for the removal of the pushrod tubed and they came out surprisingly easy. I used no heat and they came right out with a couple of taps from a small hammer. I will heat the cylinders for installation.
    IMG_20170817_1216532_rewind.jpg

  8. #8
    Liaison 20774's Avatar
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    Strange that they came out so easy. If they go in easy and aren't secure, maybe using some wicking Loctite (green??) should be used.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  9. #9
    Finally got the tubes put in and the cylinders back on. One side had to be removed and the tubes nudged out a bit because it was deforming the seal.
    Thanks to Ted Porters beemershop for the fine stainless steel tubes. These tubes went in very tight so I know they will not move or leak.
    Maybe later today get the carbs back on with new rubbers (2" radiator hose) and change the oil.
    Getting it done just in time for winter. Woo Hoo
    Attached Images Attached Images

  10. #10
    Fortis Fortuna Adiuvat Omega Man's Avatar
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    Quote Originally Posted by davelegg@att.net View Post
    I made a drift today on the lathe for the removal of the pushrod tubed and they came out surprisingly easy. I used no heat and they came right out with a couple of taps from a small hammer. I will heat the cylinders for installation.
    IMG_20170817_1216532_rewind.jpg
    Nice
    "You can do good or you can do well. Sooner or later they make you choose." MI5
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    2009 F800GS 1994 TW200

  11. #11
    I had to turn down the diameter on the drift to fit into the stainless pushrod tubes. The .618 diameter is now around .606 . Its a tad loose but worked fine putting the new tubes in.
    I used a hotplate to heat the cylinders to about 325 degrees then gently tapped the tubes in with a two pound hammer.

  12. #12
    It's alive, Its' alive
    It has been six years since my bike has been on the road and today I fired it up after resealing the cylinders and new pushrod tubes.
    I ran it on the lift for about five minutes and I saw NO oil leaks.
    That bike has never been tight since I have owned it but now it is.
    Tomorrow I am getting it off the lift and on the road for a little warm up. I can't go too far because the tags are just a little out of date but if it does as expected I will get insurance and tags later this week. This will be perfect for the 15 mile commute on the backroads to school and back.
    This was not hard at all to do because of the help and encouragement I received from this forum and a member who has passed.
    Thanks Oak. You live on.
    Pics and videos coming soon.
    Dave

  13. #13
    I finally got to go for a ride tonight around the block ( where I live going around the block is a 13 mile ride) and I could see NO oil leaks from the new pushrod tubes/seals.
    The brakes work like brand new and the auxiliary lights light up the night. It has been at least six years since I rode that bike or really any bike and now it is alive again.
    Thank you to all the forum members who have helped me.
    Dave in Kentucky.

  14. #14
    Well, I crawled under my bike tonight to see where the oil is coming from and yes the cylinders are leaking again. I noticed when I installed the right side the seals wanted to deform so I tapped the tubes out a little. I guess I should have done the left.
    I am using the stainless steel replacement tubes and I originally had the depth set to where the high part of the ring is flush with the cylinder base just like everyone said to do but for some reason that is too far in on mine. I will redo it this winter... again.

  15. #15
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    Can you make a soft angled drift and gently tap the push rod tubes out of the barrel and against the seals?
    I think I did that many years ago to fix a similar small leak.
    Steve

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