Airhead engine, trans, final drive swap question

Discussion in 'Airheads' started by Captdan, Feb 1, 2013.

  1. Captdan

    Captdan Been here awhile

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    I've got a 1974 r75 frame with a 1976 r90/6 engine and trans mounted. I've got a deal on a one owner 1977 r100s. Seems the bike has been sitting, does not presetly run and shows 40k actual miles ( all records with the bike). Question: would the r100 engine fit my frame? Would the trans fit my r90/6 engine? Would the final drive be of any use to me, either mount with the r100 installed given it can, or be used with the present r90? I looked on max BMW and the only numbers that swap out for sure it seems is the trans. I'd buy the bike as spares for my r90 cafe, with the idea of rebuilding the 100s and installing it in the r75/6 frame at some point.. Any info would be appreciated. If none of the above swaps is possible I'd pass ( as I don't need another project). Asking price is $750.00. Seems just for parts the bike is work that.

    Thanks,
    #1
  2. jbcaddy

    jbcaddy Long timer

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    You should pass on that old piece of junk. What did you say the sellers phone number is????:evil
    #2
  3. supershaft

    supershaft because I can

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    The later the better IMO regarding engines and frames. Get the bike and use the one you have now to fix up the later model. It will all swap but you have to mind what you are doing.
    #3
  4. Captdan

    Captdan Been here awhile

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    Good try..... :D
    #4
  5. Captdan

    Captdan Been here awhile

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    Well, I thought about that, but I've got tons of work on the old bike. Would the tank and cafe seat fit the r100? If so, I'd just need two swap over the headers and instrument cluster and a few ods and ends. Perhaps would be a better choice. But call me crazy, I rescued the old r90, got it working and looking great, and I'd hate to take her off the road.

    So to sum up, we re saying I could in fact use all the parts from the r100 swapped to my present build?
    #5
  6. supershaft

    supershaft because I can

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    Yup. Except for the fact that you are thinking about the entire deal ass backwards! :D
    #6
  7. Captdan

    Captdan Been here awhile

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    Yes, I know I know.... Thanks,,,,
    #7
  8. JonnyCash

    JonnyCash turd polisher

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    My SWB /5 has a 77 R100s engine, trans, final drive, and front end. It all bolted in there as though BMW wanted for me to do so. It was no harder that if I had just taken out the original stuff and put it back in.
    #8
  9. Captdan

    Captdan Been here awhile

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    Oh what the hell, I'll get it and start another project..... I'll be airhead poor, got two now! :huh
    #9
  10. bmwhacker

    bmwhacker Still on 3 wheels

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    This is my 1974 r90/6 frame with a 1978 R100S engine. I retained the 1974 kick start transmission . No problem swapping everything around. I used the 1974 wiring harness....had to do a little head scratching as the engine wiring was a little different but no big deal....Used a 1973.5 LWB sub frame. The thing has parts and pieces from too many years of BMW's to even count...a real "mutt".
    [​IMG]
    #10
  11. Captdan

    Captdan Been here awhile

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    Thanks, exactly what I needed to know. A real nice looking mutt btw!
    #11
  12. Kai Ju

    Kai Ju Long timer

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    can I have the rear drive off the R100S ? :D
    #12