Yamaha forks on a BMW F650GS Dakar

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

  1. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    I'm in jail Dad, and I like it here.............
    I can definitely say that anything over .52 is way too stiff. I weigh 180, and ride very aggressively (I came off of a Husky TC450).
    Jim, I see where you came up with the .8? spring rate. That is for BMW Dakars, which have a shorter travel than a YZ. So they need stiffer springs to keep them from bottoming out. The YZ forks have 3" more travel so you can use a much softer spring before you use the full suspension. If you put .8's on your bike, it will ride just as stiff as it did before and you'll never use the full suspension. Go to the Racetech site and instead of using the BMW Dakar spring rates, go the the YZ spring rates and add the difference of the weight between your bike and the YZ + your weight. When I add 110lbs to my wieght to account for the difference between my bike and the YZ, the highest rated spring it says to use is a .52.

    I was riding with some very good riders yesterday on KTM 640's, 690's, 950 SE's, 990's, Honda CRF's, DRZ650, and XR 400's.
    I was leading this ride through the Mojave desert. THere was about 18 of us overall, and no one ever complained that I was too slow. I actually found myself waiting for the group for up to five minutes sometime.

    Ride reports from yesterday
    http://www.advrider.com/forums/showthread.php?t=418596&page=28
    http://www.advrider.com/forums/showthread.php?p=9128707#post9128707

    Initial riding reaction (the good stuff):
    HOLY SHIT! This was the best $350+ I ever spent..........hands down. I can now ride over whoops like I was on a REAL dirtbike. Even with .48's, I never bottomed out. Whoops and rutty roads that I had to ride slow over before I was hitting at 50-60mph, and the control was incredible. Sandy washes are way more controllable.

    The Bad stuff:
    I now have to spend about $900 to upgrade my rear suspension. I think Ohlin's. I'll get another 1" of height/ground clearance and 1.5" of sag.

    Just a quick quote from a guy on a 2008 KLX 250:

    This is how I started my day, with abeer of course at 0640.
    [​IMG]

    This happened due to speed being much faster than before, but my rear suspension not liking it. Bottomed out on a jump and sucked my backpack, which was strapped down to my seat, into my rear tire, spitting beers out at the guy behind me.
    [​IMG]

    Some of the beautiful Mojave desert we were riding in.
    [​IMG]

    A map of where we rode
    [​IMG]


    TO everyone who's thinking about doing this. YES!
    It will make you love your Dakar all over again. Kind of like getting your wife a tit job....then you'll need the butt lift:wink:
    #81
  2. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    A couple of final notes and a question for Skibum:

    I have absolutely no reason to change my springs to a stiffer rate. I'm running the .48's and after about an hour of riding yesterday I took another 2 clicks off my dampening for a total of 8. I was hitting shit that was 1-2 feet deep and spaced perfectly for a wipe out if I was on my regular Dakar set up. I was walking this stuff at 50-60mph and passing guys on CRF 450's, KTM 690's and little KLX 250/300's.

    Jim, as you can see in the pic, I prefer Tecate:freaky .

    No problems with the stock YZ brake in the dirt, but I might've used only once or twice:lol3 . I can see that when riding on the street, a little more braking power might be useful.

    Skibum, what fork springs did you use? Please chime in because I would hate for anyone to buy a spring that was just going to ruin there suspension and all they had hoped to gain from the effort and money.
    #82
  3. JDRadman

    JDRadman Moto Head

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    Awesome report. Thanks for the update. I like the Tecate roost. If your going to roost your buddy, why not roost em in Tecate...you da man.

    Interesting thoughts about the spring rates and a great idea to look at the YZ + the extra weight. That is really more relevant than the Dakar reference.

    I don't think that Skibum had data on his spring rates. Just word of mouth from the guy that sold him the forks...maybe he has an update because it would be good to know.

    I am interested to see what is recommended by my buddy at House of Horsepower. I still like the idea of a progressive rate spring because of the variation in weight between wife and no-wife and the 40% on-road that I will be doing.

    Thanks for the most excellent feed back Rob. I will keep you posted of the caliper/axle developments.

    Rad
    #83
  4. Aries71

    Aries71 Adventure seeker

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    Hey Rad, i've been contemplating this mod for a while now and have been following this thread with great attention.

    I want to keep my OEM wheel and caliper as well, so I would be very interested in your caliper hanger and axle if possible, hopefully i'm not too late, let me know.

    And to throw something else in the pot: any of you guys have ABS? That's another one of my issues that i'm still not sure how to tackle, that ABS sensor thingy and how to mount it to the YZ forks.:huh Any ideas?
    I'm thinking some kind of bracket clamped to the bottom of the leg or to the axle (I think that's what Touratech did).

    Cheers
    Pierre
    #84
  5. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    Yes, do what I did and was the second best thing I ever did to my bike. Take a pair of wire cutters and cut the wires at the pump, then disconnect all fo the lines and throw it in the trash. That's wher it belongs.:lol3
    #85
  6. JDRadman

    JDRadman Moto Head

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    NOTMY... has a point, on the other hand, if you would like to keep the ABS... for your on-road adventures? There are tons of attach points on the bottoms of the forks for guards and that funky brake line routing thing that Yamaha does. It should be easy to fabricate something that was well integrated and protected.

    I don's have ABS and it is too late to incorporate it into the caliper hanger. But it isn't too late to get in on the build. Once we prototype and make sure it will all fit/work as planned we can easily run a few more. I will add your name to the list.

    I hope to get machine time this week.

    Rad
    #86
  7. Aries71

    Aries71 Adventure seeker

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    CUT it all out!!! AH AH that's funny :lol3!!!! That would be the easy way for sure, but I use the bike for commuting also and I must admit that ABS saved my ass a couple times (hot blonds in tight shorts are very distracting coming around a corner!!):evil I ride in the rain too and it did come in handy there also... or maybe I just have to slow down pay attention to what I'm doing LOL!!!.

    Thanks for letting me in on the buy Rad, very appreciated.

    NOTMY...How high did it make your bike? Is it comparable to a stock Dakar? Bit higher I imagine. Since i'll be using the bike as a all rounder height is definitely a consideration (i'd hate to fall over at a stop light LOL!!)

    Cheers
    Pierre
    #87
  8. JDRadman

    JDRadman Moto Head

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    Aries 71,
    Here is the raw data on the forks. GS = 35" and the YZ = 37" long. On my bike I am reducing the length by 1" (travel too). I have increased the spring rate on the shock and this should allow the bike to ride higher in rear too.

    After much discussion we decided that the ride height can be fine tuned (after setting the sag on both ends) with the extra inch of fork length by sliding it deeper into the triples. This is made easier by the bar risers already installed on my bike.

    All that is to say that I am shooting for a very similar ride height as my Dakar had before. You will have a bit more trail with the YZ triples so you may want to experiment with lowering the front even more than standard to reduce the trail if it steers to slow.

    Much of the improvement that I expect will come from less deflection from the more rigid front end. Think about the fact that we are going from a 41mm standard to a 46mm USD. The USD means that the area subject to the most deflection (where the lower triple clamps the fork tube) is now 58mm vs 41mm. Not to mention a much more sophisticated damping system, more travel and a lighter weight assembly.

    My riding is more in line wth what you described. Rob hits it pretty hard from what I can tell....Based on his experience with a direct bolt on, I think I will be really happy with the matching rear and some additional tuning to the set up.

    Now if we can just get the machine time to finish this up :thumb

    Rad
    #88
  9. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    Hot blonds in tight short? Please dude, you live in Ontario. One week of sun light per year and the women look like polar bears:lol3 . Just kidding, my wife is from New Brunswick (raised in Cali and looks more like a Cali beach bunny) and we spend a few weeks every year in NB and Nova Scotia. Also, Toronto. There truly are some beautiful women in Canada,but we'll keep that a secret:freaky .

    As for ride height, one of the greatest things about this swap is that you gain not only travel, but sag. I appreciate the sag as much as the added height as this is what really matters when you're at seed over whoops. THis really depends on your riding style and ultimately, it's infinitely adjustable to fit what you do.

    Mine is set to add 1" of height to the bike, and I have my triples dropped .75". When I redo my rear shock I will take that .75" out and go for the full height that it offers. I spend 90% of my time in the dirt, only hitting pavement to get to the dirt.
    #89
  10. Aries71

    Aries71 Adventure seeker

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    Well that's just it, we don't have too many of these around here, so when you see one it's enough to make you kiss the back of a semi if you're not careful LOL!!!! (thank goodness for ABS on that one!). Unfortunately we are not blessed like you guys in California where they seem to grow on trees...or out of the sandy beaches!!:wink:

    Back to bikes; it's good to hear that there is quite a bit of adjustment possibilities available, I'm not very familiar with USD forks so that's why all the questions and also I want to do this only once and make sure it'll fit my riding.
    I like your write up Rad, very informative.

    Hey...what about steering stops? what did you do? Or did you bother? I know, I just don't shut up with the questions, but good info is hard to come by on this subject even at the Chain Gang.

    Cheers
    Pierre
    #90
  11. JDRadman

    JDRadman Moto Head

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    Aries71,
    The YZ stops work as advertised with a minimal clearance issue. I removed (ground) some material on the bottom of the instrument support bracket . I cut out some material from the top of the black plastic radiator shroud with a box cutter to clear the bottom triple at full lock.

    I have risers and hand-guards on my bike. The hand guards are about where they were before, just touching the instrument cluster at full lock.

    Rad


    #91
  12. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    Just used the stock steering stops.

    The guys on F650.com would rather talk about what to do and never do it, but have all of the answers in the world:lol3 Those guys should ride more and write less, then they might have some worthwhile opinions. That's my opinion and I'm sticking to it:D
    #92
  13. JDRadman

    JDRadman Moto Head

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    The Axle spacer and nut are done. We hope to get machine time to get started on the hanger by this weekend ... we will just have to wait and see.

    I agree Mato, your bike knows what's going on...be careful :eek1


    #93
  14. Brute

    Brute Melbourne , outer east .

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    I`ve recently missed a couple of sets of wr forks on ebay so I went & bought a later model right lower fork leg ( concerns about the few that have broken ) I`d still be interested in chasing a set of yz/wr forks if I could mount my original front wheel . Please keep us informed of your axle & caliper bracket Radman .
    #94
  15. mattomoto

    mattomoto 2 wheels rule

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    yup, that is why the yamie fork is in the basement and not out in plain site of the F.:evil I did install new H*nda seals in my stock for so I can still ride it. Going out tomorrow to roost some dirt. Maybe I can barrow Notmybike...'s idea and roost my buddies with beer:rofl That is a funny write up. Nice work on your Dakar, Notmybike...
    #95
  16. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    I'm in jail Dad, and I like it here.............
    Thanks, I'm glad you enjoy another man's unfortunate loss:freaky . It felt like a good mexican friend died.

    I'm working on a new tank for my bike that is rallye inspired. It involves a new solo seat and a tank that takes the balance of the rear part of the stock seat and slightly overhangs the sides a bit. it will hold 1.6 gallons. The rear fender will be built in. Once that and my new tank panels are built which will also hold another .75 g's per side, along with a new fairing, I'll post pics. Should be ready in about a month. All Carbon/Kevlar using scrimp comstruction. Ultra light and mega strong!
    #96
  17. Aries71

    Aries71 Adventure seeker

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    I'm looking forward to seeing that!!:clap


    Cheers
    #97
  18. mattomoto

    mattomoto 2 wheels rule

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    Lose of good Mexican beer sucks! I feel your pain Brotha. That tank sounds sweet. Good luck with it.

    Matto
    #98
  19. JDRadman

    JDRadman Moto Head

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    BUMP

    Just so you all know this is still alive...

    We ran the parts last weekend and so far the pictures look good but I need to fit it up with the wheel to really be sure it works. I should have the prototypes here later this week to mock up the wheel / brake assembly. I will take pictures of the completed bike later this week and try to post them.

    Once I get the brake cable routing figured and priced out, we will total up the cost of the parts before we do a run.

    So far I have 4 contacts that want a setup. I will post the pics and prices then give it a few days to see how many we need to run.

    Rad
    #99
  20. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    Alright. So, I'm super stoked about my new suspension and it works great.

    This is now what I'm working on:

    All new body panels.
    New seat.
    New fairing.
    Another 2.6 gallons of fuel under the rear of the seat.
    New air box.
    New paint scheme.
    New rear Ohlin's long travel (300mm) shock.

    Let me know what everyone thinks, including some ideas if you have any.

    [​IMG]