R75/6 Build

Discussion in 'Airheads' started by RobboJ, Jan 24, 2013.

  1. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    Here is my 1974 R75/6 when I purchased it in August of 2012:
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    Needless to say it was in a pretty bad state. Everything was seized and rusted, the ally was crumbling like straw and the bike had been home to a family of mice.
    #1
  2. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    The mice had moved into the airbox and had been storing food in here, the L/H inlet, carb, head and cylinder...
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  3. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I started stripping it down, finding less and less that could be salvaged
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    #3
  4. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    And so it began...
    I had the frame blasted and powder-coated:
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    Those of you with a keen eye will spot the /5 headlight shell, I picked one up from eBay as I really liked the /5 lighting+instrument set up.
    I was really happy with the result of the blasting and coating, a local guy that I took it too was really friendly and helpful, and even offered to show my A level pupils round his workshop and demonstrate the various blasting and finishing processes.
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  5. isdt BMW

    isdt BMW willserv@aol.com

    Joined:
    Mar 14, 2010
    Oddometer:
    365
    Location:
    N. E. Ohio
    How could anyone be so bad to a good bike? Hope it was dirt cheap.
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  6. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    Whilst the frame was away I went to work on the wheels, rubbing them back with grillo-pad and replacing all the spokes with stainless items. I loved rebuilding the wheels, it took me back to when I ran a bicycle shop and would spend most days building wheels for customers.
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    I started putting things back together, a set of twin disk forks was my first upgrade, although the springs seemed much softer on these than on the original forks
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  7. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I had the engine totally apart, I wish I had taken more photos but during most of this process my hands were covered in black grime and I didn't go anywhere near my phone/camera!
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    I started collecting parts that I needed, I tried to clean the carbs but they were too far gone, so I bought some newer ones of a running R80/100 mono that my friend was breaking - I had to adapt the choke lever a little but they seem to fit ok.
    I also found some 800 barrels and pistons in fairly good condition, so I turned the skirt of the cylinder down a few mm until the slotted nicely into my crankcase - then sandblasted them as they were filthy. I gave them a really good clean out after - having nearly destroyed one of my first bikes because I hadn't cleaned the oil way of grit properly!
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    #7
  8. Foot dragger

    Foot dragger singletracker

    Joined:
    Dec 27, 2006
    Oddometer:
    15,248
    Location:
    chico,just below rag dump(nor-cal)
    Wow! Just for posterity you should keep track of the hours involved in this very loving bringing back of a bike from the dead. I once did a minor frame/fork swap on a 76 R75/6 as it had hit a car. It became my only purpose for getting out of bed for 3 months and consumed my every waking moment re-building/cleaning every inch of it.

    Of course for the money/time it ended up costing me I could have waltzed through craigslist and bought any number of running airheads...................but whats the fun in that?

    Best of luck and enjoy!
    #8
  9. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    Things started coming together, this was about October time when I had a break for half term. I could spend a bit more time in the workshop than the odd weekend.
    <a href="http://www.flickr.com/photos/therisingbikes/8410385657/" title="IMG_1595 by The Rising Bikes, on Flickr"><img src="http://farm9.staticflickr.com/8377/8410385657_b4802d267d.jpg" width="500" height="374" alt="IMG_1595"></a>
    It was about at this point where I really started to get an idea of what I wanted to do with the 75/6, so I cut down and TIG welded the rear subframe to accommodate my desired seat pan
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    back it went to get blasted and coated... Small waste of time and money getting it done before, but it was worth it.
    I made a seat pan one afternoon at work with some spare ally sheet and L section. I decided to rivet it instead of TIG it as the ally was quite thin and I wasn't all that confident at the time with my new TIG welder.
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    I used 3 different layers of foam to get the right feel of the seat; standard high density open cell, a layer of closed cell and a thin layer of neoprene. It felt pretty comfy and wasn't too thick.
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    #9
  10. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I got to work covering my seat, ordering some lovely leather from the wholesaler and using my grandmother's old singer sewing machine to sew it up. Working out and cutting the pattern was a bit of a job, with all the overlaps - but I was quite happy with the result, even more so knowing that I used really good, thick leather and that I had made my seat 100% with my own hands.
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  11. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I spent most of my wages in November on new tyres and parts for the bike, plus most of my free time as I knew that soon enough I wouldn't have any... It was starting to look like a bike, but still lots to do:
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    I twin-plugged the heads and fitted a neat brake splitter for my new twin disk and handlebar m/c set up. The braided hoses really set it off.
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    #11
  12. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I finally found a decent, working r75/5 speedo for a reasonable price so I went about finding all of the other speedo/headlight parts too.
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    I got quite into trawling the web all hours looking for the elusive part i needed, probably hundreds of hours over the months. I am glad I did as I found some real gems
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    #12
  13. ML WYDELL

    ML WYDELL NED

    Joined:
    Apr 10, 2009
    Oddometer:
    566
    Location:
    Looking for fuel
    Awesome work. Looks like the stuff I buy.
    #13
  14. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    Work ceased on the BMW for a while over Christmas and in the new year as me and my parter had our first son. I kept thinking about going down to the workshop but I was pretty happy just staring at the guy, waiting for him to do something rad...
    The first thing I did when I got in the workshop was give it a good tidy. Since I found out that we were having a baby I had been working very differently to my usual method. I was working up to the last minute, dropping tools where I stood when it was time to leave. I hate mess and usually have all my tools hanging in the correct place on the wall, they were currently all over the floor. I literally spent a day cleaning my workshop, hanging surfboard up on the wall and moving my other bikes and motorbikes all around until I had some order, and decent space to work in.
    Notice the cushions on either side of the bike, I tore my ACL and MCL surfing over the christmas break, so I need the cushions to kneel on. My kind neighbour (who is also a BMW fanatic) has said I can use his lift, and his expertise, which I intend to do this weekend.
    Here is the bike as it is now, I have stripped the loom, replaced many of the electrical relays and regulators and am in the process of re-wiring. Getting rid of indicators means way less wires, butI still had too much going on in the headlamp so have made a new connector box which sits under the tank, behind the coils - it is rubber insulated and easy to get to - I know it's not original but it will be perfect for me. I've also moved the key to the starter motor cover, there was already a small hole there so I used it for what I deemed as a practical use.
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    I set myself up a little 'electronics' desk...
    <a href="http://www.flickr.com/photos/therisingbikes/8411495758/" title="IMG_1827 by The Rising Bikes, on Flickr"><img src="http://farm9.staticflickr.com/8472/8411495758_eb69b9c94a.jpg" width="373" height="500" alt="IMG_1827"></a>
    #14
  15. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    I'm liking the tank more and more just the way it is, the mudguards are Ally numbers that I cut down to suit.
    I'm keeping the air box after a long debate of wether to run pods and keep the battery in the air box, but they just run way better as standard.
    I am having a think about where to put the battery, I had planned to fit a small Lithium one inside my original air box, but since deciding against pods I am starting to scratch my head. I want to have a bit of space between the air box and the mudguard, keep the frame feeling open and light.
    I welded and ally battery box for a bit of practice using my welder, and thought about locating it under the transmission, although I am keen to keep the centre stand as it is quite practical for working on the bike (even though it is not amazingly stable or practical)
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    I am thinking of making another identical one and a pair of life to match, and mounting them like panniers on the side of my rear wheel, kind of like Krausers, but shiny thick ally, and rad. One for the battery, one for my tools.

    I don't have a lot of options re: battery, I am tempted to get a small Earth X battery and put it under the seat, either behind or in front of the mudguard. I haven't seen one in real life so it is hard to imagine, but the dimensions given on the website make it seem pretty small.
    Last resort is to make a smaller battery tray and bolt it to the original battery tray mounts, but make it something that is cool to look at as well as functional.

    I need to set up the spacing on both hubs so that the wheel bearings sit right, I also need to set up valve timings and rocker gap + spacing (manually as mine are the old type of rockers) and set the brakes up, before I even think about getting it started...

    Another thing I am pondering is electronic ignition... As it has points, the dual plug coils may wear these out (even though the guy at Dyna says that the Ohm value is the same as the original single coils). If I keep the points I will have to retard the timing, and maybe inhibit the maximum advance on the A/R unit, if I go electronic it it plug and play (until I break down and get stuck).

    Hopefully I'll finish the loom this weekend, although I am worried that I might have to replace my switchgear, which looks tired and worn out (and has some different coloured wires to the original wiring diagram, i.e. no red wire at all on one...)
    #15
  16. Airhead Wrangler

    Airhead Wrangler Long timer

    Joined:
    Mar 4, 2008
    Oddometer:
    7,034
    Location:
    Back in Seattle, FINALLY
    Damn. You're brave.

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    :eek1:huh
    #16
  17. Bigger Al

    Bigger Al Still a stupid tire guy

    Joined:
    Oct 12, 2004
    Oddometer:
    8,660
    Location:
    Auburn, CA

    You gave up too soon. :deal





    :hide
    #17
  18. mike54

    mike54 You don't get me

    Joined:
    Mar 13, 2004
    Oddometer:
    14,170
    I keep re-reading, you purchased that. :D
    Good job, that's going to be one tidy bike. :thumb
    #18
  19. helion42

    helion42 Been here awhile

    Joined:
    Jan 16, 2011
    Oddometer:
    227
    Location:
    Salt Lake City, Zion Curtain, UT
    :lurk :lurk Looked like something dragged up from the ocean. Great story! It's really turning into a nice runner. :lurk :lurk
    #19
  20. RobboJ

    RobboJ Adventurer

    Joined:
    Dec 29, 2012
    Oddometer:
    63
    Location:
    Sussex by the Sea, UK
    It had been sitting outside of a barn (is that still a barn find?) with 2 r50/2's for about 30 years. I live by the coast and the salt air had really gotten to it. My friend had both the /2's, sold one on and used the money to work on the other one. I will try and get a few photos of that next time I see him.
    I had to pull inch thick bramble from between the frame to even move it from where it stood. Needless to say I had to replace a lot, although some stuff came up really well with a little bit of elbow grease
    #20