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Thread: 1980 R100 RT push rod tube seal replacement ??

  1. #1
    Registered User mysteriousfish's Avatar
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    1980 R100 RT push rod tube seal replacement ??

    The oil weeping from my pushrod tube seals (both sides) has progressed to messy leaks that I can no longer ignore. Both local shops want ~ $750 to replace them. Can's swing that, but have not torn into my motor at that level...yet! I assume the seals can be replaced by removing the heads and not the cylinder sleeves. How hard is it to do?...will study my Clymers, but any tricks to be aware of? or special tools needed?.

    I think once the heads are off, I could have the shop inspect the valves, etc. Have not had any problems with them, tho.

    Once the heads are off, does it make sense to go ahead and pull the cylinders and do the rings and base gaskets? The bike has 40k miles and I do not have the PO repair/maintenance history.

    thanks for any words of advice...
    michael
    __________
    1991 R100 classic; 1980 R100RT

  2. #2
    Administrator 20774's Avatar
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    Did you have a chance to follow any of my thread over the winter?

    http://www.bmwmoa.org/forum/showthre...opend-Overhaul

    I did a complete top end, during which I replaced the push rod tube seals. As you'll see, I did a complete change, not boring my cylinders. I had 100K and things were out of spec...maybe not on yours with only 40K. But if you go that far, it will be important to get good measurements of your cylinders to decide how you want to proceed.

    Typically, the job just to replace the pushrod tube seals is not that difficult. In big terms, you pull the head/cylinder back (slightly), remove the old, insert the new, and your done. Of course, it's more complicated than that. And the problems that I feel doing the bare minimum are 1) being able to successfully clean and reseal the cylinder base and 2) you won't have the chance to replace the two tiny o-rings that are on the top cylinder studs. They might be OK, but mine looked really squished when I finally pulled everything apart. It's worth a shot...the worst that could happen is you'll need to do it again later.

    If you're going to head down this path, I highly recommend you get Oak's top end manual...$25 a couple of years ago. You'll need to contact him via email...no website. His address is askoak at aol dot com.

    If you have any questions, please ask away.
    Kurt -- Forum Administrator ---> 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
    Monza Blue 1974 R90/6
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    I would say it depends on what you want to do. If the bike runs good enough for you now, and you just want to stop the leaks, then you can replace the seals for about $100 in parts and solvents and sealers, in an afternoon. There are a number of good photo and video tutorials that folks here can point you to. Pushrod tube seal replacements isn't a hugely complex task. A few steps, but careful labeling of the pieces on disassembly is the key to success. You need a torque wrench and the usual assortment of metric wrenches and sockets, but no special tools.

    On the other hand, if you want to go beyond just stopping leaks. Sky is really the limit. You can check valves, pistons, and cylinders. Kurt's link is a great example.

    So, you asked for advice, 40k miles, running ok otherwise, I vote for just replacing the seals, doing it yourself, and waiting for the next time you need to do seals (5 years or so) to get into valves and pistons.

    Your call!

    Barron

  4. #4
    Registered User photorider's Avatar
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    If you're going the quick and easy route, you can leave the head attached to the cylinders if you leave the 6 and 12 o'clock bolts in place. Just slide the whole thing back. Saves a gasket and some time.
    76 R60/6
    97 R80GS

  5. #5
    Registered User 88bmwjeff's Avatar
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    Quote Originally Posted by photorider View Post
    If you're going the quick and easy route, you can leave the head attached to the cylinders if you leave the 6 and 12 o'clock bolts in place. Just slide the whole thing back. Saves a gasket and some time.
    If you decide to leave the bolts at 6 and 12 o'clock, don't forget to loosen them. Leave them snug, but do not leave them at the torqued settings. I did that and pulled a stud.

    If you have good compression, I would leave the rings and top end alone, but I would replace the base gaskets. That's my two-cents. Keep in mind I'm no expert, but that's what I would do.
    Jeff in W.C.
    1988 R100 RT (the other woman)
    "I got my motorcycle jacket but I'm walking all the time." Joe Strummer

  6. #6
    Registered User lkchris's Avatar
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    The cylinder base and cylinder stud o-rings are the same age or older than the pushrods seals and all ought to be replaced at the same time. Yours could be 20+ years old and that's a lot to expect of rubber in these locations. Why do just half the job?

    It's a job a pro should have done before and it's at most a 3-hour job and therefore not $750 and the folks you've contacted are therefor not trustworthy and should be avoided.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

  7. #7
    Registered User dmftoy1's Avatar
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    Quote Originally Posted by lkchris View Post
    The cylinder base and cylinder stud o-rings are the same age or older than the pushrods seals and all ought to be replaced at the same time. Yours could be 20+ years old and that's a lot to expect of rubber in these locations. Why do just half the job?

    It's a job a pro should have done before and it's at most a 3-hour job and therefore not $750 and the folks you've contacted are therefor not trustworthy and should be avoided.
    +1 what he said. I don't know where you live but its not all that hard.

    If it was me I'd run a compression check first to evaluate rings and to some extent the valves. Assuming its within spec I'd do base gaskets, head gasket and pushrod seals.

    Just my .02

  8. #8
    Registered User mysteriousfish's Avatar
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    thanks for all the helpful replies...I have an e-mail off to Oak seeking a copy of his top end manual. I am in Portland, and the quotes were from reputable shops...Steve Prokop and Deric Cheshire. I will review Oak's tech guide, check compression first, and plan to replace the PRT, base and head gaskets all at once. Hopefully that can get me down the road a ways until I need to do the full top end overhaul ( I also have a clutch job in my future at somepoint)... thanks again...
    michael
    __________
    1991 R100 classic; 1980 R100RT

  9. #9
    Registered User richardak's Avatar
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    From what I remember from the rally in Bend, there is a fairly active Airhead community in the Portland area. I would ping some of them.

    I would second the above comments that it is a fairly easy task to pull the cylinders but leaving the pistons in the cylinders (remove the wrist pins) so you could replace the O-rings at the base as well as the pushrod seals. I would remove the heads as well just so you could have a look. Head gaskets aren't that expensive...
    1983 R100RT hacked w/Cozy Rocket My blog
    Airhead #10576

  10. #10
    Sir Darby Darryl Cainey's Avatar
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    Quote Originally Posted by mysteriousfish View Post
    thanks for all the helpful replies...I have an e-mail off to Oak seeking a copy of his top end manual. I am in Portland, and the quotes were from reputable shops...Steve Prokop and Deric Cheshire. I will review Oak's tech guide, check compression first, and plan to replace the PRT, base and head gaskets all at once. Hopefully that can get me down the road a ways until I need to do the full top end overhaul ( I also have a clutch job in my future at somepoint)... thanks again...
    A clutch job at 40,000 miles? Was this bike badly abused?

    My 1977 R100RS has 517,000 miles same clutch!
    Ambassador BMW MOA Ontario Canada
    President Niagara BMW Riders #298
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    1977 R100RS, (Retired) 1993 R100GS (just getting started)

  11. #11
    Administrator 20774's Avatar
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    Quote Originally Posted by richardak View Post
    fairly easy task to pull the cylinders but leaving the pistons in the cylinders (remove the wrist pins)
    Hopefully the circlips are external...definitely easy with a set of snap ring pliers. That was the case on my /7 rebuild, but I installed internal snap rings with the new cylinder/pistons. Not sure what is stock on BMW over the years.
    Kurt -- Forum Administrator ---> 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!

  12. #12
    Registered User lkchris's Avatar
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    A Snap-On ring compressor for push- over cylinders is only about $20.
    Kent Christensen
    21482
    '12 R1200RT, '02 R1100S, '84 R80G/S

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