What WP USD forks for the BMW F650GS Dakar?

Discussion in 'Thumpers' started by sellmeyer, Nov 23, 2008.

  1. sellmeyer

    sellmeyer Been here awhile

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    Good afternoon all,

    I am looking for feedback on a Winter project and I am soliciting information from the KTM community, specifically those familiar with WP forks. I want to swap the front end on my BMW F650GS Dakar for a WP USD setup.

    I will begin by pointing out that Touratech USA sells a 43mm USD WP kit for $2800, but I am not interested in spending that kind of money. Presently I am looking into the used market for options but I don't have enough information about WP forks to know specifically what I should be hunting. I hope the following information will paint my picture so that some community members will then chime-in with suggestions.



    My current motorbike is a 2001 BMW F650GS Dakar with Ohlins rear shock but has the original 41mm RSU SHOWA fork. This fork doesn't inspire too much confidence off road and is only tunable when in the shop. I'm looking for a fork that can take a bigger beating and has adjustment options that don't involve taking the fork apart.

    Part 1: Weight-based considerations

    440lbs The wet weight of my current configuration
    185lbs My riding weight with gear
    _____
    625lbs Standard Weight for this project

    -20lbs fuel
    _____
    605lbs Lowest weight condition when low on fuel

    625lbs
    +125lbs Touring panniers, duffle bag, and equipment (maximum)
    _____
    750lbs Maximum Weight for this project

    FUTURE ADDITIONS:

    I would like to add additional fuel capacity to this bike one day in the future, but first I want to get the front end sorted so that it can handle the added weight. *The extra fuel option is a +22L add-on from Touratech that puts the fuel into a pair of 11L tanks that hang onto the sides of the bike in front of the rider.

    38lbs 22L of fuel
    22lbs Estimated weight of additional equipment
    _____
    60lbs Maximum*Increase to above

    625lbs Standard weight
    +22lbs additional equipment
    _____
    647lbs FUTURE STANDARD WEIGHT

    +38lbs additional fuel
    +125lbs Touring panniers, duffle bag, and equipment (maximum)
    ______
    810lbs FUTURE MAXIMUM WEIGHT


    For comparison purposes, would the KTM riders care to fill in real world weight numbers for the 640 adventure and the 950?


    So, based on weight considerations it looks like the forks need to perform well within the weight range of 605-810lbs. Looking at the KTM range I know that the 640 adventure is a bit lighter than my F650GS and the 950 adventure is a bit heavier. I am not familiar with the KTM range enough to know what WP forks are on which bikes and I don't know if I should be leaning towards those on the 640 or those on the 950. I'll ask the first question:

    1) Am I better off looking at the forks on the 950 adventure since I plan to increase the weight of my motorbike well above that of the 640 adventure?

    Based upon two separate reports of similar modifications made to a Dakar, it seems like the 950 forks are the way to go-still not sure why, however.​
    Part 2: Travel or stroke-based considerations

    I believe the original setup with the 41mm SHOWA fork provides 210mm of travel at the front of my Dakar. For comparisons the 43mm WP USD option offered by Touratech is advertised to provide 250mm of travel. ***EDIT, I discovered these specs just now here on ADVRIDER:

    Touratech WP upgrade kit: WP 4357 MXMA USD Fork with 250mm. The rear shock is a 4014 Fusion with 250mm travel

    end edit****

    Whatever I find I will need to give consideration to the overall height of the motorbike after the update. I don't have firm numbers to reference, but I believe my Ohlins shock raises the rear of the bike higher than stock. If I want to maintain original geometry and handling characteristics then I shouldn't put a fork on the front that raises it proportionally higher than what the Ohlins accomplishes. As I understand it, the WP fork option offered by Touratech was meant to complement a WP rear shock with 250mm of travel. I have not been able to find out how much travel my Ohlins has, however I can say that it is shorter in overall length than the WP rear shock. By extrapolation, the 250mm of travel on the Tourtech/WP fork may be too tall for my Ohlins.

    2) Am I correct in thinking should be aiming for a fork that has between 230mm and 250mm of travel, assuming overall length is proportional to length of travel?

    It seems to me that this range is going to work best for my body's size; can't handle too much height increase here​
    3) Would it make sense to buy a fork with more travel than I want, and then manipulate the innards to decrease the travel and overall length of the fork to match the original geometry of the bike?

    Still no answer here, but it seems to me that if I get a long fork, I can have it shortened if I send it in for a revalve job, right?​


    Part 3: A discussion of specific WP options


    Based on the considerations listed above I am looking for some sizing suggestions. I am aware of 43mm, 48mm, and 50mm USD forks offered by WP. I don't know what lengths these options have nor do I know how much travel they have. This is where I need help. I am looking for the community to recommend the following:

    4) What diameter forks are best for my application?

    It seems that 48mm has become the late-model KTM standard; works for me I guess​
    5) How much travel should these forks have given the considerations in part 2, above?

    6) Based on the answers to #4 & #5, please tell me what model KTM motorbike featured these forks?




    -I look forward to some information. Thanks
    #1
  2. LukasM

    LukasM Long timer

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    Well, don't have the time to read through this in detail, but what I can tell you is:

    All 2004 and newer 125+cc KTMs (LC4-E, LC4-A, LC4-SM, EXC, SX, LC8) except the SXC use 48mm fork tubes. The most important difference are the internals like valving, springs, etc. IMO opinion I'd get the cheapest ones and then have them valved and sprung specifically for your application for an extra $300 or so (check with Zerodog on this forum).

    Another difference are the spindles on the 2004+LC4-A, which are the same as the 950/990. These that allow the use of dual calipers. Depending on how sticky of a tire you use and if you ride in the twisties much, this might be nice to have. But even with the normal spindles/single caliper there are plenty of brake option to choose from, 270mm to 320mm rotor, and 2 piston to 8 piston caliper.

    I think you would be fine with 43mm forks as well. I met some guys on big BMW GS's that used WP forks like the HPN conversions and they never had any trouble with fork flex as far as I know.
    #2
  3. johno

    johno Long timer

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    Check over at www.f650.com under FAQ section. There is a section about front end upgrades for the GS, and Dakar.
    If you want to do it without breaking the bank, maybe a set of forks off a Honda XR400R. Cartridge type, and maybe same diam as BMW ones, but longer travel.
    The other option that has been discussed on here is using Yamaha YZ450 forks. Wouldbe a cheaper option to the WP, and plenty on Ebay.

    I have a set of YZ450 46mm USD forks on my 1990 R100GSPD, and havent done any revalving. They work great as I got them.:D
    GSPD weighs around 750lbs with me on it.:eek1
    Only issue is they have 300mm of travel, which maybe too much for what you want.
    #3
  4. atgreg

    atgreg Africatwinarama

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  5. mothra

    mothra Rally Driver

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  6. LILBIT

    LILBIT Ride you must.

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    My first choice would be Showa or Kayabas not WP. There is far more options and a ton more tuners for them. There is a thread here using Yamaha yz units. I'm not a Euro hater. There's currently two KTMs in the shed with WPs.
    #6
  7. sellmeyer

    sellmeyer Been here awhile

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    Lukas, thanks for the specific input about the KTM lineup. I didn't realize they all used the same primary setup; and your idea to have them rebuild was certainly appropriate. This would allow me to choose from a broad pool and then have them fixed up to suit my application.

    Thanks Johno for the suggestions about F650.com as well as pointing out the Yamaha option. Previously I mined the FAQs on the other site; they are a starting point and I feel well beyond that at this point. I was following the Yamaha thread here as well. I may still consider this option as well.

    Mothra, I followed that thread on those 950 adaptations once it got started. I understand the authors are putting together a video about the project. I am awaiting its release for more information.

    I'm glad to see props from Lilbit on the Showas. Previously I contacted a fab shop about custom tripple trees for this project and I received recommendations for WP and Showas from a CR. I'll look more into the Showas.



    Regarding the availability of the parts, I figure I'm patient on finding what is right as I can't afford to spring for everything today nor do I need it now. As far as service goes, I have a local KTM shop that services WP stuff and then send-away options for just about anything. I'm not too concerned about the number of places that service one brand or another because I know somebody, somewhere, services any option I choose.

    thanks again for the feedback.
    #7
  8. sellmeyer

    sellmeyer Been here awhile

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    Referencing LukasM's post, I have a question:

    do all of these models use the same upper and lower clamps or do they vary with width increasing with the heavier bikes to account for bigger wheels?

    -the second question is to ascertain what set of clamps I should need.


    Second question:

    Can someone post the width of a pair of forks, as measured outside to outside at the widest part between the clamps? looking for width from a 640 or 950 here.

    -the second question is to determine if I have clearance issues with my fairings.

    -thanks
    #8
  9. atgreg

    atgreg Africatwinarama

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    #9
  10. DBM

    DBM Let's Just Ride!!

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    I have a complete 95 YZ250 Kayaba USD front end assembly collecting dust in my shop. I bought it for a DR650 motard project that never got started before selling the bike. Make me an offer.

    DBM
    #10
  11. mcgiggle

    mcgiggle Been here awhile

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    The front end off an X Challenge ?
    #11
  12. johno

    johno Long timer

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    Availability, and cost for a start.

    And I read that some people arent happy with the X Challenge forks anyway.

    Japanese/KTM are more plentifull, and therefore cheaper.
    Just look on Ebay, plenty of Yamaha, Honda etc.
    #12
  13. atgreg

    atgreg Africatwinarama

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    X-challenge forks are VERY average, budget internals, better off with something else
    #13
  14. ozadvntr

    ozadvntr Planning that trip, again

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    I have an XC and can confirm that the front end is average at best and unrebuilbabl; but the WP units I have on my special are the best.

    They are from a 620SC and are very good. They have been revalved and resprung to suit me and the Acerbis 43L tank I run. The G/S std is roughly the same weight as the F650 Dakar so all should go well there.

    Here is a Pic

    [​IMG]

    [​IMG]
    #14
  15. jesusgatos

    jesusgatos fishing with dynamite

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    I've got a complete 46mm KYB front-end off a YZ250F (same as the 450F) from a bike that I'm parting-out. Don't mean to spam, but I thought somebody here might be interested. Please nuke this if it's inappropriate.
    #15
  16. Kiwi Pete

    Kiwi Pete Adventurer

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    Gudday SellMeyer,

    We're doing this same mod on www.garagenight.tv. We're almost there and will be doing an episode on how we did it once complete. We've come up with some neat (I think!) solutions for steering lock and steering stop plus been around the houses with steering stems/tripple clamps eventually settling on the KTM 950 front end.

    Sorry, can't go into specifics with your queries but hopefully the results will be well worth it. One things for sure, it definitely looks cool :evil

    Pete
    #16
  17. sellmeyer

    sellmeyer Been here awhile

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    -thanks Pete, Looking forward to it. I had confused you with a guy in the UK who put 950 forks on his Dakar. Anyway, I'm sure to learn a great deal from your project.

    Please post here when you've completed the build-up.
    #17
  18. sellmeyer

    sellmeyer Been here awhile

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    Thanks for the info Ozadvntr on the BMW G650 forks. It seems that you are giving them the thumbs down.

    -I didn't consider them because it seems to me that BMW generally goes to a point with their product then stops short of making it really good. They must get kick-backs from the aftermarket crowd, right?

    With regard to BMW USD forks, I checked out the new $12,500 (US) F800GS with USD forks...I figured they were just like the ones on the G650, but they are not. In fact they are not adjustable in any way! They're like a crappy version of the forks on the G650. A step backwards on a bike that is several thousand dollars more expensive. BMW is quite silly.


    Back on target:

    I've updated the first post of this thread with some answers to my original questions. I still have a few questions I hope to get answered:

    1) Can anyone tell me the max width of a pair of KTM 950 forks, as measured outside-outside between the clamps?

    I need this information to look for interference problems with the plastics on my BMW.

    2) Can anyone confirm for me the overall length of KTM 950 adv (not S model) forks, along with travel?

    I've read anywhere from 210mm of travel to 230mm of travel. I need the travel and overall length specs to make a comparison to my stock forks.
    #18
  19. JAmBer

    JAmBer Adventurer

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    Woo-hoo! I'm glad someone else is embarking on this project. I have exactly the same idea and will be following this thread with interest.
    #19
  20. Luke

    Luke GPoET&P

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    The 950 forks (both S and regular) got shorter as the years went by in order to lower the bike.

    You can adjust the travel (and total height) by changing internal parts. Here's a price list, it should give you an idea of how much effort or $ is involved.
    http://www.superplushsuspension.com/a-pricing.htm
    #20