Yamaha forks on a BMW F650GS Dakar

Discussion in 'Thumpers' started by skibum_1260, Oct 23, 2008.

  1. Gravel Seeker

    Gravel Seeker Thomas

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    I used to be a big fan of the Oryx when it first came out. There was a guy over here (on the west coast) who built one and I remember really craving one too. If I'd had the USD 16.000,- the kit cost (I think it was) I would've bought it.

    Now though, I'm not such a fan of the Oryx, the line are too rounded off. I dunno, there's just something about it that rubs me the wrong way now
  2. Aquatic

    Aquatic Long timer

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    I can honestly say I hated the look of the Oryx from the first time I saw it.
  3. TobyG

    TobyG be happy :)

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    These are not reinforcements, but actually mounts for the 2 front tanks and the 2 GMX radiators.

    Yeah, the oil tank ist the aluminium tank between the engine and the fuel tank.
    The battery sits below the oil tank in a kinda awkward angle. Very hard to reach down there, but it's a Hawker, after all.

    The fuel regulator has been movoed to make space and to make it easier to access it.
    On the other side of the engine in about the same position there ist the fuse box and some electrical stuff.
  4. hasenwerk

    hasenwerk Long timer

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    Wow… sometimes Adventure Rider reads better than any novel I have read, by far this has to be one of the more interesting and dynamic threads on this site!

    I am in the research phase of my USD fork quest. I would like critique on what I am about to do to see if I am on the same page as everyone else. Yes, this is almost as long as this entire thread - so please bear with me!

    I have two bikes and this fork upgrade will eventually be on both bikes. A 2006 650 regular GS with no ABS and will have by the end of the week a 2013 650 Sertao of course with ABS. The 2006 is going to happen first. The purpose of these bikes is long gravel roads and adventure touring. This summer my wife and I will do a cross Canada trek doing the Dempster, Northern Quebec and Trans Labrador Highway. So these bikes are going to be heavy and travel on some very rough terrain at times. For this post, I will deal only with the 2006 GS.

    My plan is to use an entire Yamaha front end: forks, triple, wheel, brake, brake line from a “short head” Yamaha so I don’t have to use a shim. Instead of spending $500 on a custom axle, shims and brake holder I will spend that money instead on a 320mm EBC disc conversion and use as many off-the-shelf parts as possible for later serviceability and have money left in my pocket. The 21” Yamaha wheel, bearings and caliper setup appear to be rock solid and spares are available in almost any town unlike BMW parts.

    So far, no modding, now the modding questions.

    Fact learned from this thread: The YZ suspension has 30cm of travel and the 650 Dakar 27cm of travel, if left unmodified would result in the skid plate hitting the ground if you were to really try hard. The necessary modification is to limit the travel of the YZ suspension to about 10.5 inches (26.5cm of travel) so that bad things won’t happen after becoming airborne.

    Fork Mods
    This is where some people chime in and say WHY neuter something - which I fully agree as it limits it’s original design and involves custom parts. It seems that most people who do want to run the 30cm of travel choose to install a $1000 rear shock that allows that travel on the back end as well or installs slightly shorter dog-bones to get the back end of a tad more. The Touratech rallye skid plate replaces the under-the-engine-sub-frame and gives you about 4cm of additional ground clearance, so am I missing something here? Why not just run a standard Dakar shock and install a “shallower” engine skid plate? This way the budget stays healthy and you won’t bottom out the bike? The only mod I will do with the forks is install some 0.52 or 0.54 kg/mm springs and fresh oil and seals. Is 0.54 sufficient for a bike that will for more than 50% of the time have a bike + rider + gear weight tipping the scales at the 375kg range? What weight of oil would be correct?

    Shock Mods
    Early in the thread there was mention of a Suzuki DL1000 rear shock that could be used. These are plentiful on eBay and cost less money than BMW units. From what I have read here - the most critical measurement of a shock is it’s compressed length and that it can’t be shorter or else you might hit the tail of the bike on full compression. The Ohlins and Dakar rear shock is said to be 268mm compressed length and their stroke is 58.0 / 60.5mm respectively. Doing some math here it seems the mechanical advantage of the dog-bones gives a 3.5:1 ratio as the travel with the dakar is 203mm (203 / 58 = 3.5 ) so the Ohlin would give about 212mm of travel (someone please correct me if I am wrong - I will correct below with the correct info). The Suzuki DL1000 rear shock has a 75mm stroke so that would give 260mm of travel which could be a good thing for those who want it, compressed length is within 2mm. The DL650 shock is 1cm longer on the compressed length but seems to be almost identical to the Dakar offering a mid ground in suspension travel between the 650 Ohlin and the 650 TT WP shock. So to me, it seems that the DL650 shock might be the way to go as it’s compressed length is 1cm longer than the Dakar shock, so it won’t go up as high into the bike, travel is greater than the 650 Ohlin.

    Question what is a matched spring rate for a 0.52 or 0.54 front spring with a bike + rider + gear weight tipping the scales at the 375kg range?

    Extended Compressed Stroke Travel (@ 3.5x)
    650 GS 315mm 266 48 168
    650 Dakar 326mm 268 58 203
    650 Ohlin 328.5mm 268 60.5 211
    650 TT WP 336mm 265 71.5 250
    650 HyperPro 336mm 265 72 252

    DL1000 345mm 270 75 262
    DL650 341mm 279 62 217
    DL650 Ohlin 347mm 279 68 238


    Why isn't there decent table support here???

    Brakes
    On a non-ABS system using the original Yamaha caliper: Does the Yamaha brake line connect to the BMW master cylinder “as is”, so correct banjo fitting and correct length, just plug and play?

    Chain
    As I have a non-dakar, it is necessary to install a chain roller up front or is a chain guide at the rear sprocket enough?

    The 2006 GS, pre-modificaitons
    [​IMG]
  5. Gangplank

    Gangplank Advenchaintourer

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    And done! Pretty happy with the final result.

    [​IMG]
    [​IMG]

    Still working through a few final details.
    Need to tune in the suspension a bit. New shock so that will take some test riding.
    Brakes need to be run in a bit. New rotor & new pads so I need to work them in a bit and then see how I feel about it all. Might be swapping to the YZ banjo bolt on the master cylinder end. I'm using the F650GS banjo and compared to the YZ banjo it has a bit later hole in it. That is if the threads fit. If not I may just go to a YZ master and get a pressure switch for the brake light.

    I'm thinking now that I relocated the turn signals the holes were the old ones where migh work for mounting some running lights. :-)
  6. kubiak

    kubiak Long timer

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    any of you guys running the yz forks on the dakar running the brake cable secured to 2 points so it bends? im running it the standard yz way with the cable sliding through the loops right now but dont like the extra brake line over the dash area.
  7. kubiak

    kubiak Long timer

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    [​IMG]
    pic of the yz brake cable and vapor cable sliding through the hoops. can i mount them like a stock xrl or klr and let them bend with the suspension or do i need special lines?
  8. Aquatic

    Aquatic Long timer

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    I did this on an ABS bike. I'm sure the concept will work on a bike without the manifold/junction on the neck. I made the 'hoop' from 5mm Stainless wire.

    [​IMG]
  9. Gangplank

    Gangplank Advenchaintourer

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    Aren't you concerned that might catch in the wheel?
  10. Aquatic

    Aquatic Long timer

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    .

    Not really
    I took the calliper banjo and turned it out slightly. The hose is also quite rigid and under flex it went outwards. It took serious effort to get the hose to touch the wheel. The only way it would touch is under heavy compression(bottomed out) and something pushing the hose inwards towards the wheel. And even then the hose would need to kink to get there.
    It is no more vulnerable than the OEM setup. IMHO of course
  11. kubiak

    kubiak Long timer

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    thanks aquatic i might have to try it!
  12. kubiak

    kubiak Long timer

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    it looks like a lot of the dualsports have the brake and speedo lines bolted down and flex with the suspension so now im really thinking on doing it lol!
  13. Gangplank

    Gangplank Advenchaintourer

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    yep the "new" CR routing is to run it inside the fork and clamp it in place at the guard.

    [​IMG]

    [​IMG]

    I didn't want to route mine inside until I had the clamo piece so I did it on the outside and used zip ties to lock it in place.

    Maybe a big pic:
    [​IMG]
  14. dansin

    dansin Been here awhile

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    Mines fixed to the fork guard with a couple of cable ties and then runs through a P clip on the lower triple. I'd prefer it if it flexed up with the suspension but it just flexes out. :hmmmmm

    <a href="http://www.flickr.com/photos/62165633@N06/8676479236/" title="Untitled by dans!n, on Flickr"><img src="http://farm9.staticflickr.com/8402/8676479236_7f059a1bd5_b.jpg" width="683" height="1024" alt="Untitled"></a>
  15. Gangplank

    Gangplank Advenchaintourer

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    For people that went from a GS to Dakar height what did you do for the side stand?

    I've been looking for a used side stand but no luck.

    I was going to have an extension welded on it but its $85 (min charge). A new one is $106 at the BMW shop so I might buy one and sell my used one.
  16. michael1968

    michael1968 Long timer

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    Yes, this is how it's run on 'Rally' bikes, fixed to the fork guard or low fender and fixed to the fork leg near the lower tripple, the line flexes between the two points.
  17. kubiak

    kubiak Long timer

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    that would make it a simple mod if i do it that way. i hope i dont need to get a shorter brake line but will have to try it first. thanks!
  18. Hunter-Douglas

    Hunter-Douglas rube

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    Your pretty pictures and descriptions pretty much have me committed to making the swap.

    Thanks.
    Only 200 more pages of mind chunking details and maybe I'll have some far out idea of how to even get started on this thing. But I guess there's no :clap without the :baldy, eh?

    Edit- Off to a good start though. Looks like I found a set of '06 450f 48mm for $180. Right down the hill from me too!
    http://www.ebay.com/itm/2006-YZ450f...Parts_Accessories&hash=item35cbdb2869&vxp=mtr
  19. Lupin 3rd

    Lupin 3rd Raygun Gothic

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    I bit the bullet and bought a Dakar length sidestand when I upgraded forks & shock from GS length.

    I also have a Touratech sidestand relocation kit that I've been meaning to install for a while now, but I never get around to it. If you can wait a couple weeks you can have my Dakar sidestand for a fair price (hockey puck mod free of charge). Or just PM me your offer, I'm not sentimental. :D
  20. Gangplank

    Gangplank Advenchaintourer

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    Hasenwerk, I'll take a stab at some of your questions:

    That's what I did. 07 F650GS to Dakar with YZ forks.
    If you use 98-08 YZ125 & YZ250F & 98-05 WR250F I believe the stem length is the same as the F650, I used a set of YZ250F and didn't have to do any shim or modification to the stem. Used YZ250F bearings in the F650GS frame cups. I used the complete YZ250F front end.


    Up to you how you handle the travel and length. I had a local suspension shop shorten the travel and revalve the forks. The YZ yoke sits 1/2" higher so that takes up some of the length. I might move the fork tubes up into the triple clamp to lower the front end a bit. For now it rides fine.

    I'm not sure what you are trying to figure out here. If you want an alternative shock you have lots of options. I can get you an ELKA shock on the group buy. $907. It is a stock Dakar length shock but a really nice unit. Does not come longer than stock.

    Again, not sure what you are trying to figure out. The spring rate is determined based on SAG. The target SAG for a dualsport bike is 45-60mm (shorter for more street and longer for more offroad capability). You should only need a different spring if you can't get into that range on any given shock. Every shock mfg will have different springs for their shock. Some cross over but not all.

    The correct set up of the shock is based on your weight + bike + riding style. I can't figure how you are getting to 375kg = 825 lbs?!! Bike is 400 lbs. Are you saying that you carry another 425 lbs on the bike?


    Not on my build. The angle of the stock brake line didn't line up so I had one made at a local place.



    Not sure if it is necessary but it is recommended. The stock BMW chain roller measures 42mm width x 30mm. ID 10mm
    I got a standard off road one. But the bolt hole is different depending on your year of bike. My 2007 had a 10mm bold but most dirt bikes use an 8mm bolt.
    So I found a set of 6900-2RS Bearings 10x22x6 which had a 10mm hole and used that as a fix.



    You will also need a new mount for the ignition. The BMW has it as part of the upper triple. You can get one or make one.

    There are a few different places to get info. WayneC1's site is really good with lots of info.
    http://www.f650gs.crossroadz.com.au/ForkUpgrades.html

    There are some other places to get notes on the web. I would verify all the info though. Some of the instructions are different here and there. Some worked great, some needed adjustments for my use or needs.
    https://docs.google.com/document/d/1Jp7_mtMXo2VfIJv-QMK78fRtQz_nDLjxBq2w4jb_aN8/edit
    https://docs.google.com/file/d/0B6Di7VWbqswCcDJ6ekczWlNDUW8/edit?usp=sharing