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Thread: 1978 R100/7 Topend Overhaul

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    Administrator 20774's Avatar
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    1978 R100/7 Topend Overhaul

    Well, I guess it's my time in the barrel!! I'm looking at going to Salem and have over 100K on the clock. Have been getting somewhat worried about the valves and have had some pinging off and on. So, out with Oak's manual and we're off!

    Things have gone fairly well. I have not had the exhaust nuts off in, say, 25 years! I know, I know...supposed to be a yearly thing. But before the Internet, I ruined one of the exhaust ports because I didn't know that aluminum-on-aluminum galled. I was the first to take the nuts off shortly after I got the bike, so I'm not sure what really happened.

    Rather than take a chance, I went straight for the hacksaw. That took me quite some time to cut through and pry the nuts apart. I'm glad I did. They were dry as a bone. Guess the anitseize I put on so many years ago sublimated!

    After that, mufflers and headers. Not too bad.
    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!

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    Administrator 20774's Avatar
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    What not to do!

    My left pushrods had a wear mark about midway...guess where the head gasket was? This is wrong folks! The right side was fine.
    Attached Images Attached Images
    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!

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    Administrator 20774's Avatar
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    Some serious build-up in each combustion chamber. That's the carbon that was probably glowing and setting off the fuel. I don't have lot of experience but the exhaust valve looks to be slightly deeper into the head than the intake. Here's the left side:
    Attached Images Attached Images
    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!

  4. #4
    Administrator 20774's Avatar
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    ...and the right:
    Attached Images Attached Images
    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!

  5. #5
    Administrator 20774's Avatar
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    I was happy to see that this Sep 1977 build /7 has no base o-ring and external circlips:
    Attached Images Attached Images
    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!

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    Administrator 20774's Avatar
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    I'm sending the heads off to Ted Porter. I probably won't do much in the next few months unless I get fired up to move forward. I need to clean up one side of the exhaust threads...a little bunged up but really not bad. I have one of those metric thread file tools - part K-D2228. I just need to figure out how to use it.

    http://www.mechanicstoolsandbits.com...28-p-4189.html

    I'll also be pulling the conrods and inspecting/replacing the bearing shells. At least that's what everyone says to do.

    As some point, I'll pull the jugs and see what kind of shape the cylinder is. Again, not a great deal of experience, but I see some cross-hatching on the walls...not sure how deep it is. If I'm out of spec, I'll probably be heading for new Nikasil jugs and rings.
    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!

  7. #7
    Registered User kentuvman's Avatar
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    Hey Kurt

    Looks like a pretty neat project! You should see a lot of power with a fresh engine.

    Keep the pictures coming!
    Ken Tuvman
    Excelsior, MN
    K75s, R65LS, R60/5

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    Sir Darby Darryl Cainey's Avatar
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    [QUOTE=

    I'll also be pulling the conrods and inspecting/replacing the bearing shells. At least that's what everyone says to do.

    QUOTE]

    I pulled the conrods of last year at 500,000 miles, bearings looked great!

    Bolted them back on!

    Just sayin!
    Ambassador BMW MOA Ontario Canada
    President Niagara BMW Riders #298
    Knights of the Roundel #333
    1977 R100RS, (Retired) 1993 R100GS (just getting started)

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    Registered User mneblett's Avatar
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    Quote Originally Posted by 20774 View Post
    I'll also be pulling the conrods and inspecting/replacing the bearing shells. At least that's what everyone says to do.
    I'm not one of the "everyone" -- unless you have a rod knock, there's no reason to unbolt them, as the crank & bearings go a long time if not oil-starved. And of course, Capt. Murphy sez that if you do pull them, *something* will go wrong.

    Redoing the heads and checking iron cylinders for being out of round (and maybe re-ringing/honing if within roundness specs) makes good sense at 100K; tinkering with the crank is not needed in the absence of an indication of a problem isn't.
    Mark Neblett
    Fairfax, VA
    #32806

  10. #10
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    Good to know about the rods...I don't really sense there's a problem...not sure I would know otherwise. I recall someone saying to pull them to check...I was this far anyway. I'll give it more thought.
    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!

  11. #11
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    Great Pix

    Thanks for documenting this job so well.

    Having just done this on a '78 Motorsport, and being a "regular guy" and not being a former (or current) machinist, mechanic, airhead guru -- here are a few observations for others following the thread:

    (1) Pulling the conrods is easy, but I agree with other posters that it's probably not necessary unless you've noticed strange noises, etc. Bearing shells last a very long time. I pulled mine at over 60,000 and they showed almost NO wear whatsoever.

    (2) Oak's manual is an absolute necessity unless your name is Glaves, Porter, Cutter, etc.

    (3) Oak's current suggestion for a base-sealer is Loctite 510 - pricey, but a breeze to use (plenty of "open time"), and my cylinder bases have not leaked a drop. If you follow threads on this process, you'll see quite a few folks with problems in this area, SOME of whom probably used something else. Leaks mean "do over," at least to me.

    (4) The Siebenrock cylinders and pistons are the berries. Porter sells them. Do it now, and you'll ride this thing into the sunset. You probably already know that it's not a good idea to go "oversize" anything on a liter Airhead.

    (5) Porter does a beautiful job, and -- as with many good things, it will take awhile. From your comments, you obviously already know this. You should have -ahem - PLENTY of time to do whatever else you contemplate (such as building a full-sized, functioning Airhead out of toothpicks or something) before getting the heads back.

    (6) You can make one of those pushrod seal "installation tools" out of 1/2 (ID)" PVC, and it works great. I obsessed over getting the EXACTLY right OD mm's for the pipe, finally gave up, used PVC (not exactly right), and found out that it didn't matter that much. My seals went right in, following Oak's instructions to the letter.

    Walking Eagle

  12. #12
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    W.E. -

    I bought Oak's manual 4-5 years ago in anticipation of this. I had set it aside because I had pushed the overhaul to the back burner but picked it up again to reread the critical sections. I don't recall Oak's recommendation in the manual for a base sealer, but Ted Porter has recommended Permatex Ultra Gray.

    Yup, I've read how it's probably not recommended to try and oversize the liter cylinders. But I have to make my measurements first, then decide. Ted is my first choice, but I've gotten a few off-line comments as well about his turnaround time. Earlier this fall, I read on another forum where he turned around a set of /6 heads in two weeks. They must have caught him at a slow period. I intend to email him and get some information about the job and then really try and keep him to it. I want to get this together with time to properly break it in before the summer trip.

    I'm not sure what you mean by installing the PRT seals. The seals install themselves as far as I know. If you're talking about the collar to provide the right pressure on them, I'm not a big fan of driving that collar tighter. I will observe where the collar currently is. I also have a drawing from Oak (I've posted a semblance of that in the past) about where the collar needs to be relative to the cylinder base flange. If necessary, I will adjust by using the proper tool to move the pushrod tubes around. I've had to do that on my /2.
    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!

  13. #13
    Polarbear Polarbear's Avatar
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    Same bike here:)

    I have the R100/7 since new, with 388000m now. My heads are original and I have taken them off every 50-75000m or so to clean'em, if that! My compression is still near the top of scale. I bored it and did first oversize at 104000 with rings and valve guides, thats all. Did NOT need to, but had already bought the parts, holding'em in hand. Did all the work myself. I know I am nearing the same job someday(lol), but the bike has been amazing and surprises me how well made it is. Knowing what I know today about mine, the 100000m mark is just a well broken in engine on a /7 model. I have interest to know what the HEAD JOB cost with Ted P. .? He is well respected and I live only 3 hours from his locale, never met the man. I saw him in Sedalia at the rally this year, as he had a vendor booth. Randy

  14. #14
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    Kurt, the reason you had rub marks on one pushrod is because of the head gasket. Look at it --- it's on backwards. Flip it over.

    Been there; done that!

  15. #15
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    Quote Originally Posted by rowens816 View Post
    Kurt, the reason you had rub marks on one pushrod is because of the head gasket. Look at it --- it's on backwards. Flip it over.
    Yup! I knew that once I looked at it. That's why I said that was wrong!! This was a result of me doing a ring replacement back in 1983 after being concerned about the level of oil use. I replaced the rings with Luftmeister 3-piece rings. Since it was before the Internet, I didn't know about the orientation of the gasket and put it on wrong. It won't happen again, for sure!
    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!

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