BMW R80ST technical questions on re-assembly

Discussion in 'Airheads' started by bpeckm, Jan 29, 2013.

  1. bpeckm

    bpeckm Grin!

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    I am putting my ST back together after doing some "maintenance" and have a few questions.... I want to do a thread on the whole dis-assembly and re-assembly, which I will (eventually!), but for now I have some ho-um, somebody can certainly answer THIS type of questions.....

    First question, there is not a gasket spec'd nor a part number for said gasket between the driveshaft and the final drive. When I dis-assembled, there WAS a gasket, and every other twin- or mon-shock I have ever done DID have a gasket. I can certainly re-assemble with Yamabond or some such, but wondered what y'all have done..... (I got parts from Max, and asked them, and they said that the fiches don't show a gasket, so there isn't one, .........but.......)

    [​IMG]

    It would be a square-ish gasket with a big round hole in the middle, with four bolt holes for studs #2..... you know, the standard, every-airhead-final-drive gasket....
    #1
  2. Airhead Wrangler

    Airhead Wrangler Long timer

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    Someone speak up if I'm wrong, but I believe BMW eliminated that gasket and now advises to assemble it metal to metal with a sealant. I used threebond there.
    #2
  3. One Less Harley

    One Less Harley OH.THAT'S GONNA HURT

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    I'd make a gasket, as I wouldn't trust sealing to just yamabond or equivalent.

    BTW- I've had mine apart but don't remember what was done.
    #3
  4. Prutser

    Prutser Long timer

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    I use the gasket from the older ones on all my mono's and never had a problem with them.
    #4
  5. bpeckm

    bpeckm Grin!

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    Yeah, I hadn't thought of that... I guess I could use the old standard twinshock piece...I have used Yamabond on the inside cases of a Yammy motor, and it is fabulous stuff, but somehow I would feel better with an Old School Gasket in this application!

    [​IMG]

    04 33 17 2 311 098 GASKET ASBESTOS FREE 1 $1.79

    Price is right!!
    #5
  6. mark1305

    mark1305 Old Enough To Know Better

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    Hi Bob.

    I ran into a similar situation when I split my first Ducati 900 motor open for a spun rod bearing. Ducati eliminated the gasket in the middle of the crankcase. Threebond had just come out with the 1194 stuff. It worked so well that when I had to reopen the case to correct a shimming error, I had to make special tools up to get the two halves apart.

    Where clearances and shimming come into play, on the Ducs the allowance for the old gasket was .011" (from an unused .015" thickness). When using Threebond applied properly (thin) the allowance changed to nil.

    I'd use it and not look back.
    #6
  7. BMWrider79

    BMWrider79 Here

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    So I have a '83 ST that I'm building right now. There is no gasket used -instead you should use a sealant that is intended for torqued joints. Many kinds are on the shelves - I chose a loctite offering. BMW advised using Loctite 518 you could also use Loctite 573.
    #7
  8. bmwrench

    bmwrench Long timer

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    I believe that BMW thought there would be enough movement of the monolever rear drive to eventually destroy a gasket, so they recomended sealant. Apparently they thought sealant was immune to this.

    I've assembled them with and without gaskets. The joint didn't leak either way.
    #8
  9. bpeckm

    bpeckm Grin!

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    ...

    Thanks to all who staightened me out on the above ^ !!







    OK... so the next "technical" question.....


    If the 80ST is considered one of the best-handling airheads every built, is there ANY difference in the TRIPLE-TREE itself (not the forks, suspension etc....) ??


    The reason I ask this is that the 80ST has that same scrawny airhead top-plate for the triples that experts here deride with some regularity.... yet I don't hear a lot of talk of a better top? I know that "those who convert" to a G/S style often do a different/better front end but that is primarily for fork travel, and somewhat for brakes, than for handling.....


    [​IMG]


    The stem bearings are cross-referenced to pretty much all airheads starting with the /6 series. The actual top- and bottom units are shared with the R65 and the G/S, and vary only by some minor fasteners (for the R65 and ST headlight assembly).... but .... is it the same bottom/top dimensionally?

    Anybody care to throw out their thoughts on that?
    #9
  10. BMWrider79

    BMWrider79 Here

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    You are correct that they are the same. If you plan on doing a lot of off road it would perhaps be best to look at all the people who have done some really neat conversions to ST and G/Ss. As well, the front suspension is not the best (even by BMW standards).

    For myself adding a Toastertan top plate, http://www.pbase.com/toastertan/top_braces
    and Racetec (the US company) emulators was enough.

    If you use the TT top brace you will need to add two holes for the headlight mounting bracket.
    <table style="width:auto;"><tr><td><a href="https://picasaweb.google.com/lh/photo/DOZgwEn3NUCLYCvAvGBaB9MTjNZETYmyPJy0liipFm0?feat=embedwebsite"><img src="https://lh6.googleusercontent.com/-y1QHJuBma20/TsODRAvqmjI/AAAAAAAAB80/VILIJWtz-FA/s640/IMG_1959.JPG" height="480" width="640" /></a></td></tr><tr><td style="font-family:arial,sans-serif; font-size:11px; text-align:right">From <a href="https://picasaweb.google.com/104607105288994809461/BMWR80ST?authuser=0&feat=embedwebsite">BMW R80ST</a></td></tr></table>
    Good luck
    #10
  11. bpeckm

    bpeckm Grin!

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    Wow... that picture is worth the proverbial 1k words.... I suspected, but wasn't sure, and to see the two tops "side-by-each" is just perfect.

    :*sip*



    :*sip*
    #11
  12. bpeckm

    bpeckm Grin!

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    Are the four holes-in-a-row to provide a forward and a back place to put the standard BMW bar mounts?


    :ear
    #12
  13. villageidiot

    villageidiot Long timer

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    yes

    the toaster tan unit is a VERY nice piece, and hes a super guy to boot.
    #13
  14. bpeckm

    bpeckm Grin!

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    Ok.... another thing to put on the KaChing list.... nice indeed! .......Nothing like a little triple-porn to look at on his website..... sigh.....(yes, it is SFW....)

    :eek1
    #14
  15. BMWrider79

    BMWrider79 Here

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    Toastertan is a good dude. I stopped by his place last year just to meet him (and get a brace for my '81RS)- in fact he has some photos of it on his site here http://www.pbase.com/toastertan/vincent
    #15
  16. bpeckm

    bpeckm Grin!

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    Okay....


    ......next question....since I wasn't smart enough to take a shot of the various relays and how they fit before I tore out the whole wire harness.......does anybody have a photo or link to a diagram? I put them back and the top of the outer relay is just about touching the tank!


    We are "enjoying" a day of blizzard conditions with no power, no cable and only 3G web access.... (What on earth did we used to do....!!!! Bought a generator the other day, so at least we can have some warmth, but the gas supply is limited, so we run only as necessary....



    :cry
    #16
  17. Renner

    Renner combustophile

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    don't know that this will help, but it's handy

    [​IMG]

    [​IMG]

    [​IMG]

    I was chasing a short...
    #17
  18. bpeckm

    bpeckm Grin!

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    Perfect! I was trying to fit 3 relays onto the space where there are 2.... The other goes directly behind the vr it seems...

    :wink:
    #18
  19. bpeckm

    bpeckm Grin!

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    :evil


    ...so now the NEXT question....

    In my haste (excitement?) to strip the bike of it's wiring harness, I didn't take pitchers of how the harness goes around? through? under? the headstock.... anybody have a pic they can steer me to?

    I do remember that the harness was low, since the front turn signal wires come out of the harness and disappear down those little tubes... but I cannot figger if the whole harness comes UNDER the frame/headstock junction!

    Putting things back together.... new starter wires, all terminals cleaned, re-greased headstock bearings, etc etc etc

    [​IMG]

    :evil
    #19
  20. bpeckm

    bpeckm Grin!

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    hmmm.... just went through thread again and found this... is this the pretty-much-standard way to go around the headstock?

    [​IMG]



    That big wire hanging straight down is probably the main harness, the rest are control bits methinks....
    #20