Yamaha forks on a BMW F650GS Dakar

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

  1. WayneC

    WayneC Long timer

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    Ducked down to the garage & took a quick measurement

    To the eye wheel seems centred in forks but measurement says

    43mm from RHS fork to rim
    40mm from LHS fork to rim

    Must stress quick & dirty measurement
    #61
  2. JDRadman

    JDRadman Moto Head

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    I have completed the 3d model and met with my machine shop buddy to get the prototype made. The hanger will look a lot like the one on the Touratech website and we will make one new spacer to get the wheel centered with a new stainless steel axle. Thanks to those that gave me measurements on their wheel to fork set up. Variances of 2-4mm were noted.

    I believe that we will need a new brake line to reach the caliper since it will be a bit lower and the forks are a bit longer. I know I will need one since I already have risers on my bars and its already tight.

    So here is the question to all interested parties.
    Are you really interested? If so, I need commitments sometime next week. No money yet but a good honest commitment would be appreciated so I know how many to run. I will likely only do this once so jump on board and tell your friends too. The more the merrier or cheaper for us all.

    If your interested send me an email or PM and I will reply with pictures of the prototype when I get it back before we exchange any money. If you want to see a model of where we are so far, I can do that too.

    The kit would consist of:
    • 1 - New Brake Hanger (7075-T61)
    • 1 - Stainless steel custom axle with spacer
    You would need to:
    • Acquire a Yamaha YZ 01 to 07 fork and triple clamps and axle nut...
    • Re-spring and re-valve for correct set up. I will shorten my set up by 1" overall and adjust ride height with the triple
    • Be responsible for the bearing set-up, the new brake line and a few nuts and bolts necessary to install it all.
    All parts are provided "as is" with no guarantee or warranty. The user assumes all risks for the operation and safety of any use of the parts. Let’s say these are sold for cost, as a novelty only and not suitable for on or off highway use.

    If you’re really interested you should contact me off list. I will update my progress on the list but I don’t want to get off topic.

    Rad
    <o:p> </o:p>
    #62
  3. El Cazador

    El Cazador Mama didnt love me

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    could be interested in a pair of gs or dakar oem forks that somebody doesnt want after the switch...
    #63
  4. JDRadman

    JDRadman Moto Head

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    Mine will be available very soon...pm sent
    #64
  5. El Cazador

    El Cazador Mama didnt love me

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    ok im really on the fence on this one. I need a new front end because of a wreck. I would like to make my gs(not dakar) more offroad worthy while im at it but ive got a 30inch inseam and dont plan on putting a dakar shock in the rear. Also, I am mechanically inclined but the 6000 mile service is the extent of my motorcycle experience (though JdRadman's parts would help considerably). Honestly could this mod make sense for me?
    #65
  6. WayneC

    WayneC Long timer

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    The mod would be far better than the OEM forks

    Can you advise what damage your front end suffered ?
    #66
  7. El Cazador

    El Cazador Mama didnt love me

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    My Bike was parked and was hit squarely on the front end while the bike was at full lock. I Noticed immediatley that front wheel was misaligned and rotor was bent. I have replaced the rotor and (almost) re-aligned the forks by loosening clamps and yanking it back into place. The wheel is also just a little out of true. I have ridden the bike in the last couple of days and, while rideable, the front end feels a little off and I am exploring my options for a fix. I would still like to take the front fork off and apart and see what exactly is going on. My main concern for the yammy conversion is if I can drop the forks in the trees enough to get close to the height of a gs (and inch or two lift is ok). Im also worried that Im biting off more than I can chew because I havent done so much as change the fork oil before. Any advise would be appreciated.
    #67
  8. mattomoto

    mattomoto 2 wheels rule

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    Sounds great JD- pm sent.

    Matto
    #68
  9. WayneC

    WayneC Long timer

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    El Cazador

    Thanks for the info, sorry to hear you were an innocent bystander so to speak, sounds like the culprit did not hang around, even worse.

    It is wise to think about expertise in setting up the yamaha front end, perhaps there are people close to you who could assist.

    Personally I would not ever consider using an old style BMW RHS fork leg, but my outlook is colored by the fact I have had the axle mount detach.
    #69
  10. JDRadman

    JDRadman Moto Head

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    EL,

    The following is nothing more than my opinion, so take it for what its worth.

    You might want to evaluate the way your riding the bike now and how you would like to be riding in the future. Don't worry about the project complexity. It is not that bad and there will be a way to get it done. Figure out where you want to be first.

    If off-road is taking front seat to on-road riding, its worth considering the a change in your front suspension especially considering the unfortunate opportunity to upgrade that was presented to you by the crash and run.
    1. If your perfectly happy tooling around touring or commuting, I wouldn't even bother with the upgrade and find a set of used GS forks and get back to business as usual with the stock setup. This is a great ride either way
    2. If your interested in doing a bit more off-road than the average bear, the Dakar forks may be the ticket to a minor improvement. Stiffer springs (per my TT setup) and more travel will make a huge difference in the bike. Don't forget about the brake cable requirements (you can have mine with the forks). If you have bar risers you can drop the forks in the triples pretty much but you still need to be concerned with ride height and attitude. A longer Dakar model shock would me nice too but maybe not necessary...I just don't know.
    3. If your really wanting to make a big difference in the bikes off-road capability (plus the fun factor) and you can drop a few grand into front and rear suspension, go with the rebuilt KYB 46mm Yammy front end, have the Dakar rear shock re-worked and you have a very different moto to ride. Comfortable on the HWY at 70mph all afternoon and competent on the rougher trails and access roads. Don't forget, its still a very heavy bike. But that's why you need a 400EXC to do the knarly stuff.
    So that is my nickle perspective on the F650GS. I have owned mine since 01. It is my only street bike now and I spend 50% of my time 2-up with my wife on back roads and trails. I couldn't see spending the $$ in a 950 or even a new F800GS. My finished product isn't even in the same league with those bikes but I can go anywhere they can, do anything they can (or more depending on who is the pilot), it was fun to build and I still have the $$ in my pocket for other adventures.

    Life is so full of compromises.

    I hope that helps....but its just one mans perspective.

    Rad
    #70
  11. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    I'm in jail Dad, and I like it here.............
    I pretty much completed my swap yesterday. All that's left to do is install the caliper which is coming today UPS.

    EDIT: Caliper is now on and I took it for a ride in the field next to CSULB............What a difference! Now to get Javier (Trail Tricks) to rework my rear suspension and tune it.

    Total costs were $386 which included:

    2003 YZ 426/450 shocks with 11.8" of travel
    New .48 Racetech Springs (sock is .45)
    New Seals, Shims and Dust Covers
    New bearings
    Excel Rim
    Brake Caliper
    Oil
    Beer

    Had to also buy a new s/s brake line: $50

    New total is now $436

    SO EASY A MONKEY COULD DO IT!

    Only one custom piece needed. The yoke of the Yamaha is 3/16" shorter than the BMW. So you will need to buy or have made, a 3/16" spacer to go under the spindle nut and on top of the top dust cover.
    The top bearing of the Yamaha is identical to the BMW and fits the cup perfectly.
    The bottom bearing fits the cup perfectly also. You must use the Yamaha bearing as the Yamaha bottom bearing ID is 30mm, not 28mm like the BMW.
    Overall, the Yamaha spindle is about 1/8" bigger (stronger).

    Took 2 hours flat.

    Two drawbacks:
    1. No steering lock
    2. My friend who paid over $3000 for his TT suspension hates me...nothing some alcohol can't fix....Right Jim?
    [​IMG]
    #71
  12. trailtrick

    trailtrick goat trail rider

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    wath you going to do with the rear so does not feel like a choper Rob ??
    #72
  13. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    I'm in jail Dad, and I like it here.............
    I was going to talk to you about that on Saturday.
    #73
  14. JDRadman

    JDRadman Moto Head

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    Notmybike...,
    Cool deal, sounds like you got it done.
    <o:p> </o:p>
    I am interested in how the bike handled with those spring rates. <o:p></o:p>
    RaceTech's site says the Dakar's stock rate is in the .62 range but I can’t get that verified. RaceTech recommend a .83 rate on the Dakar with my street weight of 160 lbs. So the .48 springs are about half of what they recommended.

    While most of us will be riding on a lot less aggressive terrain on the 650 than we would on a YZ, we are still doubling the weight of the bike (low 200lbs to low 400lbs) that is riding on the same springs.

    Did you use the stock or supermoto aftermarket brake/rotor?
    The BMW OEM brakes are 300mm X 5mm thick disk and the YZ OEM disk is 250mm X 3mm thick. The YZ caliper pistons are about 20/22mm and the BMW pistons are 30/32mm but I am not sure about the differences in the master cyl. I think we would be giving up significant stopping power especially when repeatedly stopping from highway speeds like in the twisties. That may not be in issue at lower speeds in the dirt.
    <o:p> </o:p>
    And what kind of Beer would be good to know too...

    I think I will end up at about $900 bucks in my forks but far shy of the TT $3,000 set up. When I am done, we will loose 1" travel/length to cut down on the "chopper" setup, have progressive wound - .83ish springs in front, new seals wipers and valving, stock brakes, stock wheel, new caliper hanger, new brake line and new SS axle. I may get the stock rim upgraded to make it stronger too.

    The back shock is getting re-worked as we speak. Spring rate will be up about 20% and progressive wound for compliance on the street. It will also raise the rear-end a bit. This and slipping the forks deeper in the triples will help get the geometry back in check.

    Overall, I will drop less than a $1,100 into the bikes suspension and I hope I am as happy with it as you are with yours.
    <o:p> </o:p>
    I blame my buddy Quinn for all of this excessive spending. He bought a new 800GS last month. I didn’t want to drop the cash on a new bike but I just couldn’t sit still for that. So I had to upgrade…
    <o:p> </o:p>
    Rad
    #74
  15. mattomoto

    mattomoto 2 wheels rule

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    Nice bike Notmybike... I too have put my bike on a diet (well, not as extensively as yours, but getting there). Yamie fork will help a bunch and hopefully pair nicely with my Wilber's rear shock.

    Rad- my bike must know something is up... My left fork seal took a huge dump today on the trail. Nice flowing of fork oil all the way home. How's the progress coming with the brace/axle?

    Matto
    #75
  16. JDRadman

    JDRadman Moto Head

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    Sorry/happy to hear about your seal. I agree that is a protest because she is on to you. She just doesn't know how good its going to be. :freaky

    We have all of the engineering is done but we lost the machine time on Sat to a real job that pays the bills. We are trying to reschedule for either Sunday or early in the week.

    I will post as soon as I know more.

    Rad
    #76
  17. mattomoto

    mattomoto 2 wheels rule

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    No worries Rad. I just thought is was funny she puked on me today. It was so sad- blood, er, fork oil dripping down her leg. Matched the blood flowing down my shin.:lol3 AGATT, except shin guards... Gonna throw on my 661's I wear on my bicycle next time I go to the rock gardens.

    Good to get on trails in Feb. non the less.:clap

    Matto
    #77
  18. notmybikemodelname

    notmybikemodelname KOTW is a myth!

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    Jim,

    I'm doing a 300+ mile ride tomorrow to break it in. I still want the BMW brake setup. So don't count me out. I think .83 is way too aggressive. I took mine for a pretty fast and rutty ride today. I have the .48's and had to take 6 clicks off the preload. It was borderline too stiff. I used the stock yz front brake set up and it's pretty good. I ride mostly dirt so I don't use alot of front anyways.

    I'll get some pics and give a ride report tomorrow. Riding out through the local mountains to the high desert (Randsburg, El PAso Mountains, and back) 78 miles street, the balance dirt.
    #78
  19. mattomoto

    mattomoto 2 wheels rule

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    Nice, look forward to a ride report and what you think of those springs.

    What wt. fork oil are you running?

    Matto
    #79
  20. JDRadman

    JDRadman Moto Head

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    Sounds great...cant wait to hear the rest of the story...
    Have a great ride

    Rad


    #80