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Thread: 91 r100gs tranny bearing question

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  1. #1
    Registered User
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    91 r100gs tranny - bearings and upgrades

    Hello all

    I have a R100 GS tranny open to do the circlip on the output shaft and will be changing all the ball bearings while I am in there. Do not know the mileage, the gears seem to be in good shape and it shifted by hand fine before i took it apart. As well there was little metal fillings nor had he output shaft been affected by not having the circlip (front bearing still tight to the helical gear)... looks like a good buy off ebay couple of years ago for $150
    I plan to refresh this tranny, use it on the bike while I refresh the original that is in the bike now that is all okay except for having to always lift the gear shift after a gear down before being able to make another shift down; something not returning in the shift mechanism likely.

    Reading through all the articles that i could find and reviewing my configuration I would like some advise on which bearings faces to leave open to oil flow versus having seals in place, pictures on sites show different configurations.
    The configuration I found is all open both side except for:
    output shaft rear: both seals in place (I understand the outer one with the dry drive shaft, but should the inside seal be removed for oil exposure?)
    intermediate shaft rear: seal in place against the rear housing only.

    I also plan to replace the plastic shift roller with the recommended bearing skf 628/8 or 688 (8x16x5) - can anyone report that this makes a significant improvement for shifting?
    Last edited by grahamm; 02-19-2013 at 11:49 AM.
    1991 R100 GS "Bumble Bee"
    1981 R80G/S(wp4860 forks, Henderson triple clamp)
    2010 Husaberg FE450
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS

  2. #2
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    Guess little opinions out there on trannys. Going to stick to the seal configuration as found on the bearings and replace the plastic roller on the shift mechanism to a skf 628/8 bearing.

    Bearings in skf all tallied to about $110 and gaskets and seals to around 75. Getting output shaft to my favourite machine shop for the "groove" this week so when I get back late jan I can measure the bearing end play and then order the required shims... Hopefully it will be back together mid feb if the shims are stock locally.
    1991 R100 GS "Bumble Bee"
    1981 R80G/S(wp4860 forks, Henderson triple clamp)
    2010 Husaberg FE450
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS

  3. #3
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    Got the shaft done by my fav shop... 60 bucks got me the groove machined and the bit of metal removed from the top and bottom of the taper that came from the flange... Guess they welded themselves together a bit.

    Report from the shop.... Wholly crap that shaft was hardened, good quality heat treating and metal

    When I get the gaskets and seals in from max i will post up the reassembly pictures and full report of refresh cost.
    1991 R100 GS "Bumble Bee"
    1981 R80G/S(wp4860 forks, Henderson triple clamp)
    2010 Husaberg FE450
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS

  4. #4
    DaveM Dave Backmarker's Avatar
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    Jun 2007
    Posts
    48

    Transmission rebuild

    Graham, Suggest you look at http://www.cycleworks.net Dan offers bearings, tools and a video that includes fantastic tips on rebuilding an airhead transmission. I've rebuilt my R90S transmission and the tools, parts and advice I got from Dan's cycleworks site were critical to a great rebuild.

    DaveM
    1975 R90S
    2000 R1100RT

  5. #5
    Registered User
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    Location
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    Quote Originally Posted by Dave Backmarker View Post
    Graham, Suggest you look at http://www.cycleworks.net Dan offers bearings, tools and a video that includes fantastic tips on rebuilding an airhead transmission. I've rebuilt my R90S transmission and the tools, parts and advice I got from Dan's cycleworks site were critical to a great rebuild.

    DaveM
    1975 R90S
    2000 R1100RT
    Good suggestion, thanks... I missed that video is available.
    1991 R100 GS "Bumble Bee"
    1981 R80G/S(wp4860 forks, Henderson triple clamp)
    2010 Husaberg FE450
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS

  6. #6
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    Nov 2009
    Location
    Central Ontario, Canada
    Posts
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    Got around to getting it all back together

    Circlip groove added to the output shaft:








    Shift mechanism plastic roller replaced with recommended Ball bearing:








    Housing, Cover and gear train all ready for re-assembly:






    To determine requirements for shimming I used the Solder method. 2.5mm solder installed without any shims, installed covere with spec'd torque. Dis-assembly and measured resulting thickness of the solder. Shim stack calculated with .05mm end play for each shaft - used .38, .28 and .2mm shims to get the required .05 end play. 0.2mm were special order from Germany all the others were stocked in the Canadian warehouse. Took about 2 weeks for them to come.











    1991 R100 GS "Bumble Bee"
    1981 R80G/S(wp4860 forks, Henderson triple clamp)
    2010 Husaberg FE450
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS

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