F800GS - RXV Shiver'ed Fork Conversion

Discussion in 'Parallel Universe' started by Gangplank, Jul 25, 2010.

  1. Gangplank

    Gangplank Advenchaintourer

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    Hi,
    So in reading this thread:
    http://www.advrider.com/forums/showthread.php?t=524147

    I decided to take on the fork conversion. Turns out -W- was thinking the same thing I was a while back except I had planned to use some KYB forks off a YZ250F. After the debacle of going to Aftershocks at TriValley Moto only to find out Phil and TriValley split ways the night before I showed up with my forks in hand, ugh.... I decided to go this route.

    I am starting this thread because a few of us have been asking questions of -W- and this will give us our own thread to communicate in. I'm going to quote the important posts from the above thread here so we'll have the info in one easy to reference place.

    The short version is this: You can easily convert the front forks on the BMW F800GS. I used a set of Marzocchi forks from an Aprilia RXV450.

    Here is the order of things:
    Find used forks with simialr diamater (marzocchi Shiver45 forks are the same as ours but a much upgraded version of their fork)
    Take them apart
    Take the bottom foot adjuster from the donor forks
    Take it to a local machine shop along with the bottom part of each F800GS fork
    The machine shop can machine the bottom of the stock forks to fit the donor bottom (compression) adjuster
    Take the internals from the donor forks + the fork tubes from your stock forks + fork caps from the donor forks
    Bring it to a local and good dirt bike or dualsport suspension shop (I used McCoy's Offroad in Carson City, NV)
    They will put it together for you
    Be sure the add a spacer to reduce the travel on the donor forks (info is below in this thread)
    Put it back to gether
    Put forks back on
    Ride and smile a LOT!
    #1
  2. Gangplank

    Gangplank Advenchaintourer

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    Here is where -w- started + a few posts along the way....

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  3. Gangplank

    Gangplank Advenchaintourer

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    Next....

    #3
  4. Gangplank

    Gangplank Advenchaintourer

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    I actually did a bit of research on this and it is possible to order directly from Marzocchi USA. They get the parts from Italy and it would cost a lot. Good thing is replacement parts are available.
    #4
  5. Gangplank

    Gangplank Advenchaintourer

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    I decided to do this conversion. Thanks -W-!!!!!!

    The sought after forks are a pair of Marzocchi Shiver 45's. They are used on a few different dirt bikes including the Aprilia RXV 450(confirmed) & 550(maybe?), Husky WR250, and possibly GASGASS.

    I found a set off an Aprilia RXV 450 that had the stiffer springs. The Aprilia has 3 spring options. Light, reg, stiff. Info is available out there on the interwebz on this. Anyway, I put up a post on a aprilia forum and had 3 set offered to me. One from Santa Cruz and two from Europe. Seems not too hard to find.

    I have my forks apart and at the machinist now. I will be posting up pics and info once I get the quoted posts moved over. Anyway, once I get the feet machined locally the revalve work will be done by Ed McCoy at McCoy's off road center in Carson City, NV. It is close to me and he is a well recommneded shop. He does a lot of pro dirt bike riders forks and seems to know his stuff. Also a Race Tech Cetner for the NV/CA so good source for parts, etc.

    I had the same question as -W- above. Will ask Ed when I drop off all the parts. I am planning to reduce the travel on my "RXV Shiver'd" forks to the stock travel of 230mm. Once I talk to ed we'll see which upper tubes I choose to use. My guess is that I will stick with the stock BMW's since they are basically the same. Love to have the silver ones.... pics later.


    #5
  6. Gangplank

    Gangplank Advenchaintourer

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  7. Gangplank

    Gangplank Advenchaintourer

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    So just to clarify there is no need to machine the top caps. They fit right in the BMW stock forks. Here is -W-'s answers to a few questions I had re: springs, etc.

    #7
  8. Gangplank

    Gangplank Advenchaintourer

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    #8
  9. Gangplank

    Gangplank Advenchaintourer

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    Here is a post by GNP77. Not sure what forks he started with but hopefully he will post up what they were since the length needed some work on that set. Or he may have opted to buy a set of RXV forks in the end.

    #9
  10. johngil

    johngil Reseda, CA

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    Looks like you were really excited w/ your work.:eek1

    [​IMG]

    Thanks for taking your time w/ this.
    #10
  11. Gangplank

    Gangplank Advenchaintourer

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    More from him...
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  12. Gangplank

    Gangplank Advenchaintourer

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    Ok, so in the end I am going to go this route. I found a set of RXV forks with the upgraded .50 springs in them for $225 shipped to me.

    Here is what they looked like when I got them.
    [​IMG]

    Since I got the tripples I was thinking of putting the tripples on too but in the end I realized that however cool the bling factor might be... My goal is a simple and great fix.

    My F800GS feet are at the machine shop now getting worked on. It will be between $75 and $150 depending on how long it takes for them to do the work. (1 or 2 hrs of work).

    Next they will go to Ed McCoy at McCoy's off road center. Revalve at his shop is $140 and he is local so I can go back for some adjustments as needed. Other option was Superplush Suspension in SF. They definitely know their stuff too and work on a lot of big displacement desert racer's bikes.

    Here are the BMW parts in a box ready to go next week.
    [​IMG]
    #12
  13. Gangplank

    Gangplank Advenchaintourer

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    I asked -W- a few questions about the spacer and shortening the length of the travel.

    I beleive he also used a set of the RXV forks same as I am so he suggested a 40mm spacer if I wanted to keep the travel the same. From what I can find http://slorider.com/Aprilia/manuals/Specifications.pdf] online the travel of the RXV Marzzocchi Shiver forks is 298.5 mm (11.75 in). The stock BMW's are 230mm or 9 inches. So I'll be getting this info to my fork guy so he can work mine back to stock length and travel.
    #13
  14. Camel ADV

    Camel ADV Long timer

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    I started with some random Shiver 45s off eBay. Not sure of the original source. The travel is 10" which is great but the over all length is 4" shorter so some dampening rod extension are in order. -W- is shortening his rods and building stopper-spacers and I'm having to lengthen...annoying! I am still working on getting a set of RXVs to do the conversion with and simply re-assemble the random Shivers and sell them on eBay again.

    I'll got a set of HyperPro "Big Tank" front springs that are intended to be used with the Touratech 20liter tank. That is my plan in the near future so I opted to install them in the first place to save the work later. I'm 225 plus gear, plus cargo so I doubt the heavy springs will be an issue.

    I got my lower fork legs back with the feet opened up on Friday. $105 from the machine shop which is about what I expected. I'm trying to track down a good suspension tuner to do a re-valve. As soon as I tell someone that it's a Shiver swap and not in a factory application no one wants to touch it...again, annoying.

    [​IMG]

    Compression valve:
    [​IMG]

    Fits like a glove:
    [​IMG]

    A big thanks to -W- for his work with the Shiver swap. It makes it easier and cheaper for us followers to build things once someone else has done the trial and error!:freaky
    #14
  15. Camel ADV

    Camel ADV Long timer

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    Yeah, I enjoy working in garage a little too much! :wink:
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  16. Gangplank

    Gangplank Advenchaintourer

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    A bit more info....

    Keep in mind a set of RXV stock forks come with a .475 springs & there are two other options - a stiffer .50 spring or a softer .45.
    http://www.af1racing.com/store/Scripts/prodList.asp?idCategory=180

    The stock springs on our bike seems to be a .44 (or .46?) so I am going to try the .50 springs and see how I like it. From the research I have done the valve work is more important than the spring rate provided the springs are within proper sag settings.

    I need to look up what the proper sag setting are for a bike like this. Any info is welcome (sources too please... :1drink)

    I am considering putting the forks on before the revalve work so I have a reference ride on them, have the work done and feel the difference. Then make decisions from there on what is needed.
    #16
  17. Gangplank

    Gangplank Advenchaintourer

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  18. big sky mt

    big sky mt Adventurer

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    [quote\]I need to look up what the proper sag setting are for a bike like this. Any info is welcome (sources too please... :1drink)[/quote]

    Here is a quickie for the sag measurements.

    http://www.vstrom.info/Smf/index.php/topic,1539.0.html

    It's for a larger bike but should work by doing the math.
    #18
  19. Gangplank

    Gangplank Advenchaintourer

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    The basics from there....

    Excellent info. Thanks!!
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  20. Gangplank

    Gangplank Advenchaintourer

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    Got the call today.... "your parts are ready." :clap

    $130 bucks. They made a special aluminimu collar piece to hold them in the lathe. If anyone needs to get it done:

    J-B Machine - ask for Dale
    (775) 359-9856
    1450 Greg Street
    Sparks, NV 89431-5927

    Here is a pic:
    [​IMG]

    and with the bottom adjuster in place:
    [​IMG]

    Dropped them off at Ed McCoy - McCoy's off road. he's making the spacer to shorten the travel and revalve. Can't wait till Friday!!
    #20