R27: the super-slow resto

Discussion in 'Airheads' started by Renner, Jan 22, 2012.

  1. Renner

    Renner combustophile

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    [​IMG]

    '61 BMW R27
    Manufactured on Februyr 21st
    delivered on September 28th, 1961 to the BMW dealer Lindner in Blaichach.

    Despite my good intention this project has been idly occupying my garage for far too long. I'd rather be riding it.

    Maybe some computer time spent running this thread will provide a bit of incentive to keep the job rolling(?)

    As is common these days, plenty of other projects promise to perpetuate a plodding progress.
    The good news is I plan to post a plethora of pics. :clap
    #1
  2. Renner

    Renner combustophile

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  3. Cordless

    Cordless Two Wheel Addict

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    Please post progress promptly. Public pleased as punch to peruse posthaste all pictures til that one plunger putts its ppb pb pb pb pb pb pb pb pb pb pb pb pb pb pb

    CaPische?
    #3
  4. Renner

    Renner combustophile

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    :lol3
    "ppb pb pb pb pb pb pb pb pb pb pb pb pb pb pb" indeed
    :freaky

    :bow 8 minutes into the thread and already I'm being schooled by a master :bow


    :D
    #4
  5. Renner

    Renner combustophile

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    first bit of bling

    [​IMG]

    gotta go now, not sure where I left the cam and generator. :scratch
    #5
  6. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Following. :lurk

    Needs a bunch of "before" pictures.

    What is that bling in Post#5? Flywheel/clutch? It's lightened and balanced...
    #6
  7. Renner

    Renner combustophile

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    Sorry, no "before" pics, and only rumors regarding its past.
    The basket case included the rolling frame and painted sheet metal plus a bunch of new & old parts.
    Some parts duplicated, some not correct.

    This is what I brought home.

    [​IMG]

    [​IMG]

    Most everything appears to be ok.

    I've since torn down the engine and transmission for inspection because I don't know where the previous owner(s) left off.
    Nice cross-hatch on the cylinder walls. The bore averaged 2.6755 inches, slightly under spec so perhaps it was re-sleeved?
    The piston looked new.
    I sent both to Bore-Tech for their carbide bore and piston coating processes.

    [​IMG]

    The assembled head also looks new. Probably I'll remove the valves and inspect seats, faces, spring rates, and valve shaft & guide dimensions to verify all is within spec. Also checking for leaks past the valves by pooling gas in the combustion side and seeing if any gets past the seats.

    I removed the transmission cover but am waiting for bearings before I actually pull the gear shafts. No sign of rust.

    [​IMG]

    I removed the crank and found the slinger clean. Dan at Cycleworks inspected the crank which checked good, he replaced the rod bushing.

    Dan also lightened the flywheel as shown above.
    Richard Sheckler recommend this for better acceleration off the line.
    Bore-Tech shaved the cylinder top .040" for me at his recommendation as well.

    I've worked a few of the smaller issues: rewired the left switch assembly, corrected both wheel bearing stacks, bought and installed some missing hardware etc.
    ...but like the bike, this project has been going nowhere fast.

    On the + side: yesterday I finally managed to remove the aft cam bearing.

    [​IMG]

    Eventually I'd like to commute on the bike. Work is less than 5 miles away.
    #7
  8. Kai Ju

    Kai Ju Long timer

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    My first bike was a 1954 R25/3 that I bought when was still living in Germany, back in 1972. Bought it for the equivalent of about $15.00. Rebuilt it without restoring it, kinda wish I had brought it with me when I moved to the US.
    Looking forward to watching yours come back to life.
    That flywheel is a work of art. Almost a shame to hide it behind the clutch.
    Looks great so far.
    #8
  9. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    But still, they are as before-ish as we'll get on this phase of the project. I've never seen the insides of a thumper before.
    #9
  10. FreeTheBeast

    FreeTheBeast Shunpiker

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    :clap That's a nice bike! They don't make them like this anymore. You'll be so pleased to ride it once it's done.
    #10
  11. Renner

    Renner combustophile

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    Quite right.
    though I don't have a handle on the bike's past, I've managed to accumulate a brief history with it.

    #1 lump with the generator out

    [​IMG]

    driven end of the oil pump shaft lives under a cover near the dipstick.
    pushrods exit the upper pair of holes

    [​IMG]

    coil ignition. these points weren't so good.

    [​IMG]

    fitting the master link to this cam chain may be a breeze compared to the type 247 challenge

    [​IMG]

    clutch on display

    [​IMG]

    and a closer look.

    [​IMG]

    Sprockets look serviceable.

    Apparently I stopped taking pics during crank removal (what was I thinking).
    #11
  12. Beater

    Beater The Bavarian Butcher

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    The first trip better be to the bar. :lurk

    :lol3
    #12
  13. mykill

    mykill odd

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    Fantastic project! I might be hitting you up for info soon-ish. I'm supposed to assemble one for a friend, he is paying me with a Montesa Impala!
    #13
  14. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Wonderful pics. I was a bit unsure of the details of a Thumper so I did a Google browse this morning and familiarized myself. I was really puzzled by the "Dipstick and oil-pump drive" holes nextto the pushrod tube holes... :eek1

    The more I look at older BMWs the more I see familiar parts used on later models. Great heritage.
    #14
  15. davorallyfan

    davorallyfan Commonist

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    Hmm have you ridden one? They are one of the most gutless bikes ever made.

    Pretty yes... but effort and reward???

    I dont mean to piss on your fireworks just letting you know.
    #15
  16. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    250cc, all of 13hp. Gutless, yes, but they have such charm...
    #16
  17. Mike V.

    Mike V. Adventurer

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    "Charm" indeed. I'm pretty sure speed or bhp is not the catalyst for this excellent build. This will be a stunning addition to your already impressive herd Renner. Wes knew he was turning this bike over to the right owner.
    #17
  18. Infracaninophile

    Infracaninophile Finding My Way..

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    +1. Definitely following your excellent thread. Pics are great.

    Tom
    #18
  19. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Oops, 18hp, 13kw. A bit less gutless.

    Here is a nice Wiki quickie on the R27:

    http://en.wikipedia.org/wiki/BMW_R27

    :rofl
    #19
  20. Renner

    Renner combustophile

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    Thanks guys. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    <o:p></o:p>
    For the record, BMW lists an optimistic 18 hp at 7,400 rpm. <o:p></o:p>
    Unladen weight with full tank is about 356 lbs.<o:p></o:p>
    Giving a power loading ratio of nearly 20:1. <o:p></o:p>
    Once I hop on, W/P=30+<o:p></o:p>
    <o:p></o:p>
    As a point of reference, the BMW S1000RR runs I think, somewhere around 2.3:1, unladen.<o:p></o:p>
    <o:p></o:p>
    This alone is the single greatest incentive I face today for engaging in a personal weight reduction program. :nod<o:p></o:p>
    #20