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Thread: 1978 r100

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  1. #1
    Registered User godfather's Avatar
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    1978 r100

    My quest has brought me to yet another airhead, a 1978 R100. Bone stock except for the Dyna III ignition. No bags, fairing or windshield.

    ... second owner, 15,700 miles. The bike gets about 60 miles a year for the past 5 years.

    The Good:

    Fires right up.instantly! (after charging the dead battery)
    No smoke
    Rides and shifts good.
    Clutch good
    Brakes are good
    Cosmetically 7/10
    Tank lining good
    Never crashed
    All lights/electrics work
    No dents or dings in the rims
    Cables operate smoothly

    The Bad:

    All 4 push rod tube seals leak bad.
    It may have leaky front and rear main seals too. There is oil at the front of the engine at the base of the front cover and rear in the trough area
    There is oil weeping at the cylinder bases at the engine block, not leaking, just weeping.
    Idles a bit rough under 2500 rpm but smoothes out above that (carb clean/rebuild?)
    The mufflers are rotting from the inside out at the weld by the taper... the metal is expanded and obviously rotting
    Tires are good but old and have to be replaced
    Needs a battery
    Steering head needs adjusting/tightening probably grease too
    There are scratches and chips here and there but I think it will clean and polish up nice.

    All in all it seems to have a lot of potential.

    I am not a mechanic, but I do know what end of a screwdriver to hold...somewhat mechanically inclined and a lot more patient than I was when I was young.
    That being said...
    Are the main seal leak problems a major undertaking to fix? The engine is not oil soaked just greasy oily front, not as bad at the back.

    Pushrod seal seem straight forward. I imagine its pull heads, pull jugs (with pistons still in or out?) remove tubes and seals, clean degrease everything, install new seals, reassemble with all new gaskets and torque, then re-torque after X miles.
    Probably a good idea to de-carbon everything while its apart too.

    What say you?

    Thanks.
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

  2. #2
    Administrator 20774's Avatar
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    You pretty much have the top end job down...I recently did a top end on my /7 and posted the thread earlier this year. I would recommend getting the top end manual from Oak Okleshen. While the process is pretty straight forward, having a step-by-step guide is helpful...there are some good hints in there as well. If I were going to all that much trouble, I'd probably removed the pistons and rings and measure everything...the bike only has 16K miles so one would think that there's essentially no wear but you never know. I found my lifter surfaces pitted...but that was after 100K miles...it's about miles but it is also about the oil that is used.

    As for the engine seals, I might be inclined to clean things up and get a better sense of the rate of leakage. The front seal shouldn't be bad...I was just working on my Dyna III this past weekend as was in far enough to see the camshaft seal. Brook Reams had a recent posting about changing the seal using a nifty seal pulling tool. The rear main seal is a bit more involved...plus you have the oil pump cover o-ring. To get to that, the transmission, clutch, and flywheel have to come out. Be sure and read about how to block the crankshaft so it doesn't move forward when the flywheel is off.
    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
    Registered User jad01's Avatar
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    Quote Originally Posted by Godfather View Post
    What say you?
    I'd say clean the outside of the engine up carefully, including the back of the transmission (and if you can, the shelf underneath it where the neutral switch is located), and then ride it for a few hundred miles and watch it carefully. Cleaning things up will allow you to pinpoint what seals/gaskets/orings need changing, and some new things may come to light as you ride it that you will know to take care of while you've got it apart.
    Jim
    '78 R80/7 and '84 R100RS (Blues Brothers), '86 K75C (Icy Hot)
    '90 and '93 Red Mazda Miatas ("Jelly Bean" and "Red Hot")
    '96 Giant Upland (big Kendas & freshly greased bearings!)

  4. #4
    Registered User 88bmwjeff's Avatar
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    If you haven't done it already, join the Airheads club (airheads.org). Then, look and wait for a local tech day, or better yet--host one. There will be plenty of knowledgeable people on hand to help and some will have the specialized tools needed to make the job easier.

    When I got my bike back in 04, it needed most of the engine seals replaced. The first job I did (within a month of purchase) was to pull the tranny and send it off for repair. While I was there, I replaced the rear main seal and oil pump O-ring. If you go slow and methodical, you should be able to do the work. Take plenty of notes and photos to help you get things back together. Also, be willing to purchase the necessary tools to perform the task properly. That will save you a lot of time and effort. There are a few companies that make specific tools, so you don't have to purchase them from BMW.
    Jeff in W.C.
    1988 R100 RT (the other woman)
    "I got my motorcycle jacket but I'm walking all the time." Joe Strummer

  5. #5
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    Having recently purchased 1 '78 R100/7 here are some suggestions:

    Drain and replace ALL fluids, including brake, trans, driveshaft, and rear drive.

    Replace air filter and oil filter.

    repack all of the grease in both wheels. My front looked as though it hadn't been lubed in 20 or more years.

    Do all of this before you ride it at all. You can carefully monitor everything else and then do the labor over the winter.

  6. #6
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    Oil pan

    All good advice,especially on ordering Oak's top end manual.The only thing that I would add is to remove the pan and give it a good cleaning.That,and check the oil pickup bolts for tightness.
    Russ

  7. #7
    Registered User godfather's Avatar
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    Great info...THANKS.

    I am waiting to hear back from the seller if he will accept my offer or negotiate further.

    If he accepts, it will be in my garage, licensed and insured by Friday, degreased and all fluids changed by Sunday (yes I have a new oil filter and crush washer). Tires, mufflers, push rod seals, cables and all tune up parts ordered by Sunday night.

    I hope to know something by midweek....
    Attitude is everything!
    1978 R100/7
    08' V-Strom 650 great light weight tourer

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