R90/6 scrambler build

Discussion in 'Airheads' started by lagfish, May 9, 2013.

  1. lagfish

    lagfish Adventurer

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    Hi All :D,
    Last year I acquired a 1974 R90/6 with 70k miles on it for my second bike and rode it almost everyday for 6 months. Even though I really enjoyed the bike and there weren't' any issues with it, it's not in the best condition. The frame has rust spots on it which I've painted with a brush but looks like crap when you look close, the engine is full of grime from the leaking seals, the seat cover had several cracks in it, and the paint on the tank is cracking around the filling hole because the gasket is shot.

    I wanted something nicer, unique to my personal tastes, but still keeping the classic style of the R90/6 that I fell in love with. I don't really enjoy the cafe look and think that it has been overdone. I like the scrambler look and would have some practical uses for the dual sport tires since I plan to do some trips off the beaten path. The goal was to make it into a classic GS. I do have pretty good fabrication skills, so I will be doing most of the modifications myself. It will save some money, plus I think the more you put into it the more you will "know" your bike and love riding it.

    I made some sketches on paper then photoshopped the following for my build concept:
    [​IMG]

    I will be doing a complete frame-off resto-mod with the following major things:

    -Snowflake alloy front and rear wheels (was too lazy to photoshop the rear wheel) from an R100
    -Dual front brakes with ATE calipers. Since a /6 right fork slider with mounts for the brake caliper is pretty rare, I will be buying another left fork slider and modifying it to take a caliper on the right side. I will keep the master cylinder under the tank but modify it so it has two outputs for the dual caliipers
    -Shortened subframe to give it a sportier look. I will fabricate another frame (sub-subframe) that will bolt onto the sub-frame. The sub-subframe will have aluminum side bags attached to it.
    -Custom seat and cover
    -New paint on tank
    -Scrambler type handlebars and newer controls
    -Powdercoat fork sliders, wheels, frame, and sub-frame.
    -Raised front fender from an R100, chopped rear fender from undecided yet
    -custom headers or at least new mufflers
    -/5 headlamp (expensive!!) or new and much smaller speedometer

    I think it's a pretty ambitious project, but I'm young and don't have a family so I'm pretty motivated and have lots of time to work on it. Hopefully you guys can provide some encouragement as well.

    Wish me luck! :D
    #1
  2. lagfish

    lagfish Adventurer

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    First an introduction to my workspace. It's a corner of a storage unit that I've rented. For shelving, I've stacked some cinder blocks and used OSB for the shelves. I think it was less than $20 for materials. While I would like to have a nice garage to work in for this restoration, I don't think it's necessary and you've got to work with what you've got.

    Here is a photo showing my little corner and the bike with a large tank I picked up. It's a lot more dented than I anticipated, so I will probably just sell it and get another one that's not as dented. I also took the carbs, cylindes/heads, and oil pan off on a previous day.
    [​IMG]

    Here's what the bike looked like by the end of the night.
    [​IMG]

    One thing I anticipate that will be a major PITA will be reconnecting all the wires back tightly into the headlamp.

    Next time the engine will come out and the frames, front end, and wheels will be separated. I hope you guys will enjoy this build!
    #2
  3. Houseoffubar

    Houseoffubar HoFmetalworks.com

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    Looks like a good candidate! Be sure to seal up that crankcase, before you get debris in it!
    Have fun:clap

    BTW, check out Elite-less's build. He built two beautiful bikes in a space smaller than what you are working with. :D
    #3
  4. apt13

    apt13 Been here awhile

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    #4
  5. lagfish

    lagfish Adventurer

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    Thanks!
    I have in fact seen the CRD bikes, and was the base for my photoshopped image. The one thing I wanted to change about their scramblers was that I think the typical flat scrambler seat does not work well with the large BMW tanks. There is a large step going up from the seat to the tank and looks weird to me. Maybe changing it to a curved seat doesn't make a true scrambler, but I am just trying to build the bike that looks the best to me! :D
    #5
  6. lagfish

    lagfish Adventurer

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    Couldn't work on the bike over the weekend because I sprained my neck. But today I made some good progress. I was able to take the swing arm, subframe, and loosen the front end with the tools I modified:
    [​IMG]
    BTW, the two large nuts that keep the front end in place were probably the tightest non-seized nuts I've ever encountered.


    Here's what she looked like by the end of the night:
    [​IMG]


    Next time the engine will come off.

    Are there any simple things I should fix/replace now that I got the engine and transmission apart? The engine was running fine, and the transmission seemed ok, aside from the fact that it would slip into neutral sometimes between gears. The engine has ~75kmiles on it.
    #6
  7. Pokie

    Pokie Just plain Pokie.

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    While the cylinders and heads are off, I would likely have the heads done (all new valves, new exhaust guides, new springs). If the seats are the originals, I would have them replaced with hard seats if they look like they are recessing.

    I would likely re-use the cylinders but have them honed. First oversize rings and file them down to .010" end gap and re-use the pistons.

    I wouldn't mess with the transmission unless you feel really strongly about it. If you decide to do the transmission, I'd replace all the bearings, the shifter pawl spring and all the seals.

    Just an opinion.
    #7
  8. Roach Carver

    Roach Carver Been here awhile

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    I am sure you know that those rims have a certain value being Lester mags? You could sell/ trade those for parts if you were so inclined
    #8
  9. SERE Nate

    SERE Nate Been here awhile

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    Looking forward to watching this build.
    #9
  10. Rockman

    Rockman Been here awhile

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    Given a choice I wouldn't go for snowflake wheels on a scrambler if you are actually going to use it on dirt roads. I've destroyed 2 sets of these just from small (fist size) rocks on dirt roads. This includes a 4" long split in a front rim.
    #10
  11. lagfish

    lagfish Adventurer

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    My original plan was to use them because I though they looked really cool. But the more I looked at it the more they didn't look right on a scrambler. I think they draw too much attention to the wheels/tires, which already look pretty busy because of the knobby tires. I guess from a practical view, spoked wheels are also better. BTW, does anyone have a pair of spoked wheels they want to sell / trade for Lesters? :D
    #11
  12. lagfish

    lagfish Adventurer

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    Gotcha. Is it recommended practice to use oversize rings with a standard size cylinder? When I was making a model sized engine, I machined the rings so that they are the exact same diameter as the cylinder, then split and spread them so that they provide a circumferential sealing force on the cylinder but once they are inside the cylinder there is pretty much an even pressure all the way around the rings.
    #12
  13. lagfish

    lagfish Adventurer

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    I managed to get the engine, wheels, and forks off today. I've also been taking apart and cleaning the carbs.

    The PO broke the top part of the idle jet off, leaving the threaded part inside the carb. I am trying to tap a left handed thread into it and remove it by turning a left hand thread socket cap into what's left of the jet. The jet also seemed to be seized, which is probably how it broke in the first place.

    [​IMG]

    I've also been reworking the original concept. I think I like this look more:

    [​IMG]

    The more I look at the original concept, the more the large tank seems to dominate the bike too much. It looks almost like a streetfighter with the short seat and large hump for a tank.

    This rear suspension configuration will allow me to use a short modern rear shock and give a very progressive spring rate. The total travel will be something like 5" - while not really comparable to modern adventure / offroad bikes, it's about the same as the original R90/6.
    #13
  14. Roach Carver

    Roach Carver Been here awhile

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    I actually have a 74 r75/6 with spoke wheels. Shipping both ways could be prohibitive though. The spoke wheels are available on ebay. If you think of a price you would take for them (no tires needed) PM me.
    #14
  15. bizalich

    bizalich Adventurer

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    hey man:
    i have a r75 that was rebuilt/customized by Untitled Motorcycles last year. since i am living overseas without any real tools, workshop, or help... and since i am not that experienced with working on my bike, i decided to have them do the cosmetic upgrades and initial tuning. Now i have the bike with me here in Italy, and it is rad. The bike is not running right now, and i am trying to figure it out, but that is another story...

    I am stoked to see you taking this on, and the CRD-style scrambler is a great inspiration. I respect you for digging into the bike, and customizing it to make it yours.

    If I could give you a couple of points of advice that i learned on my build... it might help you...

    First, i love the custom seat, being a little thicker near the tank. my custom seat is similiar, but when i am actually sitting on mine and the seat is compressed, the front part comes up and there is a gap between the seat and the tank. it is kind of a bummer, and when i get some money, i want to make a new seat-pan or something to help combat this. So, try to craft a seat so that doesnt happen.

    Second, Untitled builds their motos with a /5 style headlight, but it is a repro... much cheaper, and then the original speedo fits inside with a simple hoseclamp. i siliconed mine in for a better fit. but, it is an elegant solution that does not involve buying some super expensive headlight bucket. it does mean that you need to change the wiring and simplify everything, similiar to what all the euro builders are doing. I have no idea HOW to actually do that, but i can say that it works well on mine, and inside the headlight bucket there are only a minimal of wires and fuses... like 4 or something. its nice. HOWEVER, if i had it all to do again, i would use either http://jvb-moto.com/rocknroll/?page_id=30 a headlight shroud from JVB. i have seen them in person and they look INCREDIBLE. check out the fotos... or, i would think about a r80GS headlight assembly with tach, ignition, and clock... http://www.stephenbottcher.net/BMW/gs1.jpg i think that would be pretty rad on a scrambler.

    Third, i have a close fitting hugger rear fender... and it is a pain in the ass. looks great, but kinda sucks. Basically, run a high fender like you have in your renderings, but make it go all the way to the swing-arm to keep dirt, rocks, water, etc from blasing your battery. Making sure the rear tire (especially if it is a knobby) clears the shorter subframe is pretty important at full compression of the rear shock.

    i really like the battery remounted lower in the place of the centerstand. you dont have a centerstand then... but whatever.

    Also, consider going with some slightly longer-than-stock rear shox. i got stock length, but wish i got some longer for quicker turn-in. i think the bike turns in slower also because of running Dunlop K70 tires. It might be even more exaggerated with knobbies. You can measure your shock length, but i believe stock is 13.5 inches. I have talked with works performance, and they can make any shock length you want, but from my research a 14" or 14.25 would be good. Too long, though, and you run into drive-shaft problems.

    anyway, just food for thought. Good luck with the build!

    rob
    #15
  16. lagfish

    lagfish Adventurer

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    Thanks for the advice! Do you have any pictures of your bike that you want to share?

    Does your seat pan go all the way to the front of the seat?

    Not sure how I feel about rewiring the whole thing. Although the connectors on the current bike are pretty tired and it's probably not too much more work to make a new harness vs. trying to make the old harness fit the new turn signals, lights, and speedo I plan to put in.
    #16
  17. bizalich

    bizalich Adventurer

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    hey man: here are some pics of my bike that i snapped last week with the cell. they are not really specific to the seat/seatpan, but if you want, just ask and i will take some specific seat/seatpan/tank photos. FYI, i dont really have a "seatpan"... the bottom of my seat is a solid formed unit, but it comes off the frame with 4 loctite screws--there are studs coming off the seat, and they connect thru tabs in the frame. the underside of the passenger area of the seat has a scoop cut out for the rear wheel at full suspension compression.

    For the wiring, i have never done it either, and it does seem like it would be kinda daunting. However, from looking over my "simplified" wiring that the London boys did, it does look suprisingly straighforward. I can take some pics of the inside of my headlight, and you can compare that to a stock /5 headlight and see the difference.

    Also, for more inspiration, check out the bmw that La Corona motorcycles did... pretty clean and fresh. The non-bmw tank kills it for me, but the rest of it is pretty well done.

    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
    #17
  18. lagfish

    lagfish Adventurer

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    That's a clean looking bike! I'm digging how the gold pinstripping is picking up the patina of the badge. Do you have any issues with the battery placed under the transmission with regards to dirt and rain?

    Do you know where I can pick up a repro /5 headlight bucket?

    I'm thinking of using something like these for the seat mounts:
    http://www.mcmaster.com/#standard-vibration-damping-mounts/=mzem33

    I think what makes the most sense for me is for the wiring is to modify the stock harness. I've given up on the idea of trying to keep parts unmodified so that I can convert it back to stock in the future. The original purchase price of the bike will be a small fraction of the labor I will put into it so I'm going to commit to this customization and do whatever is needed.

    I've got like 50 different bikes I've saved into a folder for inspiration and the La Corona bike is definitely one of them.
    #18
  19. bizalich

    bizalich Adventurer

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    hey: thanks! yes, i originally wanted to paint the tank, or strip all paint and clear coat it, or something... but my girlfriend talked me down from that ledge and pointed out that this is the original paint, and the bike has been in my family since it was new. so, i left it, and just cleaning the tank when it is dirty and leaving the patina.

    anyway, i have not had any ill effects of the battery placement. the top shelf of the battery box does collect a fair amount of road dirt and now there is some rear transmission seal leaking, so the oil that drips down catches the dirt. The good part is that the design is so open, that i just reach under there with a rag and wipe it clean. When we rode it from London to Italy, we did like 4 days in pouring rain... no problems.

    as far as the /5 headlight bucket--i've got no idea. The guys at Untitled Motorcycles keep it a pretty closely guarded secret, for some reason. it is definitely not a BMW part--maybe Ural? sorry i cant help you on that-- but maybe if you called them they would sell you one? PM me if you want their info.

    i think your seat mount idea could work good... perhaps better than the solid-mount that i have. i don't notice much vibration through the seat, but damping-mounts couldnt hurt. i can take a picture of the seat mounts and post them.

    the only thing i would say about my seat is that the foam is too soft. it was cut from the original foam, then a thin new layer put on top, then the leather cover... this saves cost, saves time, etc... but I would like to have a firmer foam. I weigh 175 lbs with riding gear. For most of the riding i do, it is not that big of a deal, but the padding is not my friend after 5--6 hours in a day. in fact, in the pictures above, you can see where the foam is starting to pack out from my thighs. so, the take-away is think about the type of riding you are doing, and get a seat that works for you.

    and also, i too had a ton of different bikes and designs in a folder that i had gathered over a couple years... then i moved to europe, sold all my stuff, live in a small apartment now. so, instead of attempting the customization myself, it made sense to have Untitled do it. Props again for taking on the project!
    #19