Beginnings of a fork swap
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  1. #1
    Member mmclaughlin's Avatar
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    Feb 2014
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    Flagstaff, AZ
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    Beginnings of a fork swap

    Hello All,

    I got to start making parts to begin my fork swap this weekend. I have enough to take measurements for making final parts a couple of weeks from now.

    I am swapping out to triple clamps from a Yamaha XVZ 1300 (Royal Venture Star or somesuch) and forks from a BMW F650.

    Here is a comparison picture of the TW200 upper triple clamp on top of the XVZ part:



    The XVZ uses 43mm forks and the F650 uses 41mm forks, so shims are required. I have one test shim, a full set will be made later.

    Here is the shim:



    The shim has lips on the ends so that it will stay put while adjusting fork height. Here is the test shim partway inserted into the lower triple:



    The XVZ triple clamps look massive compared to the TW parts, but because both triples are aluminum, the pair weigh less than the TW stock parts. I don't have a good scale to give actual numbers, but you can tell just by picking the sets up.

    The XVZ steering stem actually has the same diameters (for bearings) as the TW, it is just a little longer. Here is how much extra sticks out:



    There is room on the shaft to remove a little material and make sure that there is enough room to seat the new tapered roller bearings that will go in. The shaft seems to actually take the stock bearing. That is handy for now, but the stock bearings are going to be replaced, anyway.

    I do not know if I can cut metric threads; I will have to check with the friend whose lathe I borrow time on. If I can cut metric, I will extend the existing threads down. If I have to cut US threads, I will eliminate the metric threads entirely and cut new threads on the "extra" meat sticking out (between the current threads and the top bearing seal).

    For those who are curious, the F650 forks a 10mm more stroke than the TW200 (170 vs. 160). V-Strom forks are 43mm diameter and 150mm stroke (10mm shorter than the TW). The XVZ triples have less offset than the TW triples, but the F650 forks have more offset, so I think I will end up about the same trail as the TW or maybe an extra 1/4" of trail (no complaints from me). The V-Strom forks have the axle directly in line with the fork, so using them would increase the trail about an inch. The F650 is close enough to work with; I though the V-strom forks would be too much. On top of that, I found F650 forks for a decent price and V-strom forks are expensive.

    I will end up picking up a little extra room between the forks. When they are fully on, I will take measurements and pics and let people know if there is enough extra room for a TWW mod.

    Still to do is a new front axle, some form of modified wheel arrangement and fitting a proper sized brake disk (the BMW uses 300mm, I think I can make a Yamaha 298mm fit up if I can't use the BMW part). And, of course, I still have to put an engine in it....


    Matthew

  2. #2
    Member mmclaughlin's Avatar
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    Feb 2014
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    Hello All,

    I made new shims yesterday.



    The shims fit just fine. The fork is mostly on but the steering stem still needs to be shortened.



    There is not a real axle in this photo, but enough to allow me to start taking measurements. For those who are curious, there is about 8 inches between the fork sliders. A rear tire would fit, but the mounting points for the fender would need to be shortened or removed. They are about 9" from the axle which puts them at the widest part of the rear tire.

    The tire in the photo is a 4.00 wide tire.

    Matthew

  3. #3
    Senior Member Leben's Avatar
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    Feb 2013
    Location
    Iowa
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    264
    Matthew, you are building a very interesting bike. I look forward to seeing the progress. Looking good so far.

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