Ultralight R1200GS Adventure hybrid.

Discussion in 'Some Assembly Required' started by Nick V, May 22, 2020 at 5:10 AM.

  1. Nick V

    Nick V Who dares, wins.

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    For about six months, I've had an idea in mind. I wanted an HP2 Enduro - but as everyone who's tried to buy one second-hand without extensive contacts has learned the hard way, they are made of pure Unobtainium, and cost stupid money.

    With that on the table, I thought: Why not build my own? I know these bikes backwards, and their construction is reasonably straightforward.

    My first step was to look on the internet for ideas. Within five minutes, I'd discovered that that idea wasn't original, either. Airhead and Oilhead-engined specials abound!
    Which is a good thing, because what I saw made me REALLY want to go ahead.

    Jump to February of this year. The first engine-donor possibilities that came up were a low-mileage 2011 R1200R, and a low-mileage 2008 R1200S.
    Both would have been unquestionably good for the role, but both were also around the ZAR 60K to 65K mark. For me, that was too rich.
    I set an alert on a local classifieds site for BMWs in a lower price range. Two months later, a jewel popped up: a crashed, uninsured 2011 GS Adventure. I managed to pick it up for ZAR 27 500. (For contrast, if you're selling one of these in good nick here in South Africa, you can easily get ZAR 100 000 to 105 000).

    [​IMG]

    A couple of weeks later, I started looking for Japanese or Austrian dirt bikes to use as suspension donors. I wanted a rolling chassis or non-runner, minimum of 250cc.
    I quickly got bogged down in year models and technicalities. Steel or aluminium frame? What spec suspension? Which parts could I use for the project, and which could I re-sell?

    Learning more and more, it seemed Kawasaki KXs and KDXs were the most common, with Yamaha YZs and WRs second. I eventually got lucky: I picked up a 2006 WR250F that had thrown a rod: ZAR 5000.

    [​IMG]

    I've devoted a lot of thought to the frame configuration. I originally wanted the suspension donor to be a Honda CR or CRF so I could use the aluminium frame. But on balance, I moved away from the idea of building a frame more-or-less from scratch.

    I also stumbled across 'Motorcycle Handling and Chassis Design', by a British author named Tony Foale. Some excellent info in there - just what I needed.

    Due to COVID-19 and lack of space, I haven't been able to do any wrenching, but I have formulated the bare bones of a plan:

    - The project's frame will use the modified front half of the standard GSA rear main frame, pieces of the GSA front sub-frame, the WR's headstock, and the WR's aluminium rear subframe. The subframe doesn't have to be stupid-strong - this bike will be single-seat, and light on the luggage.
    - To get the front suspension geometry right, I'll be using the GSA engine as a jig, in combination with careful measurement. I want a slightly more aggressive head angle than the HP2 Enduro.
    - I'll be using two different sets of wheels: the GSA's standard 17" rear and 19" front for offroad, and 3.5x17 / 6x17 alloys from a K1200S for Sunday-morning mountain passes.
    - Bodywork will mostly be WR250, with better wind protection and a taller screen.
    - Lighting will be aftermarket LED, with auxiliary fronts powered through a Hex ezCAN.
    - Minimalist exhaust and Power Commander for a bit of extra grunt.

    With an anticipated 120 BHP and a target mass of 165 Kg, it should have a power-to-mass figure to rival an S1000XR - and make ShiftCam-engined GSs look silly.
    Now the work of actual frame design must start.
    #1
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  2. Gedrog

    Gedrog 1000 mile stare a 1000 stories to tell

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    #2
  3. Nick V

    Nick V Who dares, wins.

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    I know, it's completely insane.
    There is demand for these bikes, and BMW gives us the R18. Does anyone else see the marketing logic - or lack thereof - in that?

    The value of a British HP2 in UK Pounds doesn't quite translate to what you'd pay over here. A decent one can be had for around R140 000 (or roughly the same as a low-mileage 2014 R1200GS LC) - if one is available!
    Having said that, there is deep satisfaction in knowing that I can build a better bike for me, for about a quarter of that.
    #3
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  4. JimVonBaden

    JimVonBaden "Cool" Aid! Supporter

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    This should be fun and interesting! :thumb
    #4
  5. Gedrog

    Gedrog 1000 mile stare a 1000 stories to tell

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    Just to think during the recession in 2008/2009 you could pick up 950 Super Enduro R's and HP2 Enduro's for £6K now people want silly money because these are awesome bikes, even the G650-X Challenge once the suspension is sorted & G450X's were all fantastic bikes that came out of that era but all we get now is bigger fatter horrible overweight pigs even the new G310GS is bloated.

    But keen to see what you do

    To date this has been my favourite build maybe this one will top it, who needs a T7 when you can build your own
    https://advrider.com/f/threads/help-me-achieve-perfection-wr450-twin-adv-conversion.1140255/page-74
    [​IMG]
    #5
  6. Nick V

    Nick V Who dares, wins.

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    I've worked for motor manufacturers. Their approach is sad, but understandable.
    Their designs - even specialised ones like the HP2 series - are committee-driven exercises, designed to appeal to the largest possible segment of that particular market. Motor manufacturers don't think in terms of 'The Best', or even 'The Most Enjoyable'. Their key words are 'Marketable', 'Saleable' and 'Profitable'.

    To be that, their bikes literally have to be all things to all people. Jeremy Clarkson had a joke about design by committee that went something like: "We can't decide whether it's best to include features A, B or C. Aha! I know! Let's use ALL of them!"

    I like the G310GS a lot. :D I once had a very enjoyable scrap with a friend up the Rooi Els Road, in Cape Town. I was on the GS, he was on an S1000R. He couldn't get away from me.:rofl
    But its suspension is terribly, terribly basic, and in ZAR, it's way overpriced for what it offers.

    I think I saw another thread here in the SAR section where an Italian crew built something a lot like that. It had hand-made aluminium bodywork.
    Very sexy. :-)
    #6
  7. Gedrog

    Gedrog 1000 mile stare a 1000 stories to tell

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    Rooi Els Road is a proper leveller between big and small bikes a friend used to dish out beatings for the rest of us on his RD350, post it's resurface in the 90's, but before it was resurfaced it had a few places where you had to check the underwear afterwards. It was probably comparable with the Bainskloof in it's current state.

    What makes @MotoPolo bike great, it's like your plan, building a bike from an engine upwards where as the @gpmucci T7 creation is taking an existing T7 and modifying it, not that it isn't a great looking bike, but what makes the @MotoPolo bike great is the engineering and planning that went into it.

    Don't get me started on Manufacturers KTM has probably the sneakiest business plan
    Build the 790 Adventure R has an MSRP of $13,799 good enough suspension
    Release a limited 790 Adventure R Rally for $19,500
    Offer the parts to upgrade your bike to the Rally specs just the suspension components is upwards of $5,798

    Every now and then I watch the vid when I feel homesick
    #7
  8. Dino de Laurentiis

    Dino de Laurentiis Working on it

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    While I agree that MotoPolos bike is a special achievment in itself, you're really selling the gpmucci bike well short of what it is. By the looks of it, the gpmucci certainly had A LOT of engineering and planning into it as well, built upon many years experience of racing desert bikes. In many aspects, it's almost a completely new bike, what with a new subframe and seat position, new suspension, new tanks, the nav tower, etc etc etc, plus all the focus on easy serviceability, all while lowering weight substantially. Both are very special bikes, and it's not really fair to put them up against each other.
    #8
  9. Gedrog

    Gedrog 1000 mile stare a 1000 stories to tell

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    Not to hijack the thread, make no mistake I don't downplay GPMucci's bike it is an awesome piece of modified machinery great respect for the man's skill (Suspension was already fitted when he got the bike) remember the bike was commissioned by Kapriony Team and he had loads of pre-existing experience, but not everyone here says I like the engine characteristics of this bike and I like the handling of that bike let's marry the two with my own chassis as a first project.

    Just some other projects using the same process of modifying the bike to something that the person wants like GPMucci
    https://advrider.com/f/threads/inte...fr-and-the-ultimate-x-country.1208814/page-12
    G650-X Challenge built by a teacher first project bike to do a RTW trip. Husky clutch cover used due to the bearing made of cheese on the original X
    [​IMG]
    Airhead Boxer

    https://advrider.com/f/threads/airhead-dakar-rally-bike.893613/
    [​IMG]
    #9
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  10. Whale Rider

    Whale Rider Been here awhile

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    Subscribed :photog

    WR

    200Kgs if you are going to carry any petrol
    #10
  11. Nick V

    Nick V Who dares, wins.

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    I've given that some thought.

    Your bike definitely has one of the more elegant solutions I've seen - both in terms of using available space, and lowering the centre of mass.
    If I start out with the WR250 tank, that gives 8 litres. If I can manage a permanent tank on the bike that holds 12, I can get to 20 litres - the same as a K25 R1200GS.

    I also have a spare F800GS fuel tank (16 litres) and subframe that will do the trick for longer journeys. The ability to fit it would net me 36 litres - 4 more than a K25 R1200GS Adventure.

    One thing I definitely want is the ability to fill through a single fuel filler.
    What I'm thinking is:
    - The 'everyday' fuel filler will be the one on the WR250 tank.
    - WR250 tank linked by a large-diameter pipe to a main aluminium tank under the seat.
    - Fuel pump and filter will be mounted inside the main fuel tank.
    - If the F800 fuel tank is added, it will be linked to the main tank by suction feed (naturally, it will also have its own separate filler cap).
    #11
  12. Whale Rider

    Whale Rider Been here awhile

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    That's what I did with the YZ tank made a fitting that had a 3/4" hose fitted to it so it fills both tanks. Note the tank doesn't push all the way up to the steering head and had to be heated and reshaped on the inside to make it fit. I made a fiberglass panel to fit in between the front of the tank and steering head. Air filters are under there.
    Transfer Pipe.jpg
    Tank Cover.jpg
    WR
    #12
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  13. Whale Rider

    Whale Rider Been here awhile

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    @Nick V
    Seeing as you are using a 1200 engine some of the later 1200s had front sub-frames with standard forks R1200R and these parts are off a R Nine T not sure what the rake would be. Seeing as the engines are a stressed member this
    sub-frame looks like it bolts onto where the telelever bolts on.
    upload_2020-5-25_20-26-14.png

    upload_2020-5-25_20-26-39.png

    WR
    #13
  14. Nick V

    Nick V Who dares, wins.

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    The thought had occurred to me. :-) Technically, it's a very strong case.

    Financially - at least in SA - it's a non-starter.
    Considering the cost of BMW repair parts over-the-counter, the only viable ways to get that front frame would be to:
    A) Buy a second-hand RnineT (Not an option. The Saturday morning 'Cafe racers' who ride to be seen at coffee bars pay a premium for them.)
    B) Buy a crashed RnineT from an auction house (Not an option. Rebuilders snap them up to rebuild for the Saturday morning 'Cafe racers'.)

    For me, it's far easier and cheaper to work out the suspension geometry theoretically, then use the engine as a jig to fabricate a new front frame portion using the WR headstock.
    #14
  15. Whale Rider

    Whale Rider Been here awhile

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    Just be aware that the width of the triple clamps on the WR are not that wide. Thinking of you wanting to have interchangeable wheel options.
    I used the engine as part of my jig. When I did mine the position of all key components was in the same place as Mr BMW designed (he has more money for development) the bike IE foot pegs, rear shock mount, steering head location.
    I just added some more rake. (I already had an 1100 with a 21" front wheel so know it works.)
    Then built the frame around these locations.
    Steering Angle.jpg
    Frame Start.jpg
    Studied a lot of the RR900R photos I could find.
    BMWR900RRMore[1].jpg
    WR

    Not trying to Hi-Jack you thread just throwing some ideas out there.
    #15
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  16. Nick V

    Nick V Who dares, wins.

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    Quite the opposite! :D I don't consider it hijacking at all - this is exactly the sort of feedback and advice that the project needs.
    #16
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  17. LocuL

    LocuL Gnarly Infantry

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    Nice
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  18. Husky360C

    Husky360C Been here awhile

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    In keeping with the BMW tradition since BMW corporate decided the motorcycle division would either make money for a change or be dissolved, back in 1996.
    #18
  19. Lurkio

    Lurkio Adventurer

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  20. DiggerD

    DiggerD DougFir from SuperDuke Days

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    I will have to say I chuckle every time I see the title of this post.

    Thanks for keeping a smile on my face.

    :D
    #20
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