Sorting out my R90/6 (sprouty115)

Discussion in 'Airheads' started by sprouty115, Sep 13, 2017.

  1. sprouty115

    sprouty115 Long timer Supporter

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    Perch arrived in great shape and with remarkably similar wear to the throttle-side. I had it on in about 45-minutes, 15 of which was me trying to get the grip off without ruining it. Which I did...
    20190620_121213.jpg

    Now I have a spare clutch perch with the dog-leg lever. It will just collect dust in my basement so I'll be posting it in the flea market soon, unless anyone here wants it? Does $20 (plus shipping) sound reasonable? Just PM me if you want it.

    NOTE - see that faint grey lines on the right hand edge of the perch assembly? The top one is a scratch and the one below that is a small crack. The crack doesn't seem to effect anything as it's certainly not structural. I'm sure it could be filled and painted.
    20190620_121245.jpg
    20190620_121322.jpg
  2. sprouty115

    sprouty115 Long timer Supporter

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    More stuff -

    Yesterday, before the perch showed up I decided I wanted to be able to install my under-seat tray. The problem is that when I switched to the Enduralast charging and electronic ignition system I mounted the reg/rec in the same location. So that meant I had to relocate that first.

    20190619_102904.jpg

    Now there certainly seems like there should be space on the side of the bike behind the side-cover (and there is) but it actually took about 3hrs of slight adjustments to make sure the clearance was balanced between...
    - the fender and tool tray
    20190619_140251.jpg

    - the clip on the frame
    20190619_140303.jpg

    - the cover, which needs to be tipped in and perfectly aligned to slide into place.
    20190619_112846.jpg


    Eventually, I found just the right location and with some left-over bits of aluminum and brass I got it monuted.
    20190619_140241.jpg

    This obviously looks too homemade/erector set construction for me, but it will do for now as a test. Then after a couple of rides to make sure everything is good, a proper single-piece bracket will get made.
  3. nobbylon

    nobbylon Long timer

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    Can you not make a flat bracket and mount underneath the rear of the backbone? Tray would fit and it would look tidier. My Boyer has been mounted there for 20 years with a zip tie.
    Should be more than enough cooling if you mount it to a flat ally plate?

    BE5CF32F-94A4-4839-9B71-C031163919FA.png
  4. sprouty115

    sprouty115 Long timer Supporter

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    Oh, and I almost forgot - while I was playing around with all that I had to pull the tank to get some access to the wire loom. And that's when I discovered my master cylinder was leaking...so that is now on "the list".

    Considering the brakes are truly tough on this bike, I'm weighing my options. Right now I'm somewhere between sleeving the bore down and dropping in a 2nd disc.

    Decisions, decisions...
  5. sprouty115

    sprouty115 Long timer Supporter

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    It's hard to tell from the pic, but it has fairly tall fins on the other side. So it didn't seem like it would fit on the side of the backbone (like the Dyna coil does) or directly under it, between the frame and air cleaner cover.

    I can give it another look though just to make sure, as that certainly would look cleaner.

    Edit to add - that location is also much hotter than behind the cover, which is something to consider.
  6. nobbylon

    nobbylon Long timer

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    If you go double disc go to a 16mm MC with 38mm calipers like a 90s set up. Works superbly with braided lines.
    Bigger Al likes this.
  7. sprouty115

    sprouty115 Long timer Supporter

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    You have a 90S, damn! And that color!

    Well, that is certainly an option I'm considering. Btw, please don't post a link to a whole front end - my wallet knows how little control I have.


    Back to the R/R - that spot on my bike is currently occupied by the ignition control module. Though it is smaller and might be easier to relocate if th R/R fits.
  8. nobbylon

    nobbylon Long timer

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    I bought a new 16mm MC 2 years ago from Germany for €350 ! ridiculous price but it works and doesn’t leak which my old one did. I’ve had the 90s for 20 years now, my all time favorite bike but I’m also a fan boy for anything /6.
    I put a braided line and recon’ MC on my 75/6 but the single disc just can’t compete with the twin disc set up. My old MC could be re sleeved and I’m looking out for a r/h fork leg to do the conversion but they’re like Unicorn’s teeth and whoever has them seems to think they have the holy grail.
    Those levers look great now on your 90 btw. It’s always a small victory when something else gets sorted :)
    sprouty115 likes this.
  9. Solo Lobo

    Solo Lobo airhead or nothing Supporter

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    For future reference, my trick with grips is to use the blow-gun attachment for my air compressor, that typically lifts the grips right off.

    When that doesn't work, I shoot in a little WD40 and work the grip back and forth until it slides off
    sprouty115 and WRC51 like this.
  10. Bigger Al

    Bigger Al Still a stupid tire guy Supporter

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    Brake cleaner is my go-to for grip removal/installation, but rubbing alcohol works nicely as well.
    sprouty115 likes this.
  11. sprouty115

    sprouty115 Long timer Supporter

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    I ended up using WD40 as that was the closest can of slippery fluid with a small red tube I had that I could feed into the grip.
  12. sprouty115

    sprouty115 Long timer Supporter

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    Back to the leaking master cylinder...

    As much as the different levers "bothered" me, the fact that I now had a mess under my tank was an order of magnitude higher in terms of things-that-needed-to-be-delt-with.

    What a mess:
    20190620_151756.jpg

    So off it came:
    20190620_161811.jpg

    Probably a good idea, because there was corrosion and the seals were full of crud.
    20190620_161847.jpg

    I gave the casting a good scrubbing with
    Simple Green and then took it to the soda blast cabinet. Over all it looks ok but there is definitely some pitting inside the bore:
    20190620_170008.jpg

    Called it quits for the day, but will consider my options in the morning:

    - hone bore to remove pits and order rebuild kit
    - re-sleeve and rebuild
    - re-sleeve and drop down in bore size to improve the feel of the system
    - big single disc
    - two discs

    Not on the table right now is handlebar MC...
  13. beemeruss

    beemeruss Russ Supporter

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    My '76 R90/6 is one of my favourite BMWs. Alas, it is now a parts donor for my '78 R80/7 and '78 R100RS. My R80 has the same ATE setup as yours and if I were to find a leak in my MC, I would go the resleeve down in size for closer to adequate braking power. Just my $0.02
    Russ
    sprouty115 likes this.
  14. sprouty115

    sprouty115 Long timer Supporter

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    It would be a pretty easy decision if I knew what to order for replacement seals. 12mm? 13mm? What part numbers?
  15. mslim

    mslim If it's worth doing... it's worth overdoing

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    Been there, Done that. My bore looked like that. Didn't seriously consider honing. Tried to buy a rebuild kit from local San Fernando long time dealer, was told it was a "waste of money" cough up $400 for a new m/c. Didn't believe that spiel. Bought a rebuild kit from Max, sent the piston and seals to Mark Frappier, assembled m/c and bled the brakes, has worked perfectly six years now. No leaks. Didn't futz with changing the bore size. My brakes work fine for me but maybe it's just because I've never ridden anything modern so my expectations are low. I'm just glad to have dual discs on the front and, no it doesn't feel "wooden" to me.
    sprouty115 and Square1 like this.
  16. nobbylon

    nobbylon Long timer

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    Totally opposite experience. Rebuilt once and lasted a couple of years, rebuilt again and lasted a month even after honing. Sick of the MC modifying my frames paintwork I bit the bullet and went new. The failures of these 40+ year old bits of steel shows the importance of changing brake fluid regularly to stop rusting.
    I nearly went the handlebar conversion route but happy I didn’t. It keeps the bikes originality and as your 90 looks in good shape it would be a shame to see it go non original. I’d clean up the backbone and then hammerite it with some gloss black before rebuilding.
    mslim and sprouty115 like this.
  17. sprouty115

    sprouty115 Long timer Supporter

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    I don't think I can make the swap to a handlebar mounted MC. It's just too far from stock. I could deal with a re-sleeve at a smaller bore if it was easy to get seals. But if not, then it has to be stock or a dual disc setup.
  18. nobbylon

    nobbylon Long timer

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    rebuild kits are easy enough to get but at this point I’d go the re sleeve route and save yourself sh@t in the future. You can also then give yourself time to accumulate a double MC, a disc, right caliper and a Unicorns right front leg.
    sprouty115 likes this.
  19. nobbylon

    nobbylon Long timer

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    Not found a suitable place to get a re sleeve here in the Netherlands or Uk, anyone?
    And in the US?
  20. mslim

    mslim If it's worth doing... it's worth overdoing

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    Aforementioned Mark Frappier and possibly Apple Hydraulics in the US. Would think that there must be a vintage brake cylinder machinist boffin in the UK. Check with sports car club blokes. They should know someone capable.