An Unholy Union: DR forks on a G/S

Discussion in 'Airheads' started by elmoreman, Jan 22, 2008.

  1. elmoreman

    elmoreman takin' a break, boss

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    The original idea for this came from Crankshaft, who, a few years ago installed a cr250 front fork on an 81 g/s .
    <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    <o:p>So his idea planted the seed, but I thought that the process was out of my league. I mean, I can change the oil and everything, but taking things apart to that degree was daunting. Some time goes by, and I end up meeting Aaron at his cold and rainy Ironhead Rallye, of which SethS and I were the only participants. At the fine meal afterwards, we got to talking about his g/s conversion, and how bad the forks and braking are on the stock g/s, and he just happened to have a DR650 front end in the barn in good shape. With a promise of assistance along the way, I decided to go for it. I thought it would be great to learn more about my motorcycle, about the art of modification, and hopefully make the bike more suited for a run on the TAT and Baja next summer.


    I got the forks and triple tree from Crankshaft, the rotor and wheel from a bike salvage in Georgia (expensive but it great shape), and the caliper from ebay (10 bucks).
    [​IMG]

    At first measurement, I realized that the forks were really long, like several inches long, but since the DR650 forks are designed to be shortened (along with the DR650 rear end), they make a good match for the modification. In no way was I interested in lengthening the rear swingarm. I didn&#8217;t want to permanently modify the bike, one reason why I have kept all the stock parts as well (basically an entire g/s front end from wheel to headlight assembly&#8230;and no&#8230;its not for sale).

    [​IMG]
    First step was taking off the g/s forks. No big deal&#8212;Ive always had an easy time taking things apart. It&#8217;s the putting things back together where things can get tricky. After a call to Jesse at Keintech, I learned more about the DR forks, downloaded the manual, and got to work.

    The DR forks are designed so that if you shift the position of a spacer from the top to the lower fork leg assembly you will shorten the fork length. Jesse thought that 2 inches wouldn&#8217;t be too big of a spacer, and recommended some 1 inch iron pipe, available from any hardware store (you could use PVC spacers, as many people do, but Jesse recommended against it, especially with a more durable, easily obtainable alternative). I borrowed a pipe cutter from work, smoothed off the edges on my yard sale (free) bench grinder (it is an old washing machine motor with no switch), and got my spacers.

    the cutting:
    [​IMG]

    the grinder:
    [​IMG]

    The finished product:

    [​IMG]

    The triple tree is too long, but before I dealt with that I wanted to make sure that the forks wouldn&#8217;t be so long as to mess with the geometry of the bike. I reassembled one of the forks without oil, put it in the triple tree, bumped it out an inch above the top plate, and measured. From the bottom plate on the g/s fork to the axle is 22.75 inches, and the length from the DR bottom plate to the axle is the same, within a few millimeters. The fork diameter will go from 36mm to 43mm.


    One leg on for sizing:
    [​IMG]

    So it looks like it will work. Prep stage is complete, now to sort out a spacer for the top of the steering tube to accommodate the extra stem length&#8230;the bearing fit&#8230;attaching the G/S headlight assembly&#8230;the front brake&#8230;

    I&#8217;ll gladly listen to any words of wisdom as the project continues!

    </o:p>
    #1
  2. datchew

    datchew Don't buy from Brad

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    awesome. :lurk
    #2
  3. Stagehand

    Stagehand Imperfectionist

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    Wow- so cool-- I'm really interested in how the spacer wil lwork, as well. I've got an old KTM set of forks I want to put on the XT, and since the KTM neck is 1/2 longer than the XT's, I'm curious about the same thing.

    So no trouble matching GS races with DR bearings? or did you slide the GS bearings onto the DR stem?

    :clap
    #3
  4. Solo Lobo

    Solo Lobo airhead or nothing

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    If you are interested, I traded emails with a guy in CA (can't remember his shop's name right now) who make custom stems for triple clamps for $125 or something... if you were thinking you didn't want to make a spacer that is...
    #4
  5. Kokopelli

    Kokopelli Yeah, right!

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    Just a quick note on your grinder. You may already be aware of it, but these grinding wheels should not be turning too fast. I friend has a piece of metal plate in his forehead to cover a hole left by an exploding wheel. He was wearing safety glasses at the time. The wheel he was using was driven by a vacuum cleaner motor, which admittedly may be spinning way faster than your motor. Sorry if this is old news and doesn't apply here.
    #5
  6. Solo Lobo

    Solo Lobo airhead or nothing

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    Here's a shot of a spacer, (sorry for the hotlink Robb!)

    This is a ADVR member's bike...

    [​IMG]
    #6
  7. Cordless

    Cordless Two Wheel Addict

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    I will keep up with this project.

    So this is what takes the place of installing the GoldValve emulators. When we meet this summer, let's compare your DR front end on your g/s with the GV emulators on mine.
    #7
  8. elmoreman

    elmoreman takin' a break, boss

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    Right! I've got the emulators in the basement as well, so I have a lot of options, which is good :thumb
    #8
  9. elmoreman

    elmoreman takin' a break, boss

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    That is sweet! A friend has a small lathe, so I need to find out if this is something he could handle, and Crankshaft has a lead on someone as well. I'll keep that nice unit above in mind, though.

    As for the bearing issue, I haven"t sorted that out yet.

    Solo--Do you know how the above ADV member sorted that out?
    #9
  10. Solo Lobo

    Solo Lobo airhead or nothing

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    No, but I believe he used a Honda lower tripple and a custom upper. The problem is that you will end up with a bit of compromised handling... the offest of the R100GS (at least) is either 36mm or 38mm, and the one that Robb used was 20mm (I think)...

    Here is his page

    http://robbmcelroy.com/machine.htm

    You will loose some steering lock as the forks are closer to the frame by 16+mm's as well as the fork legs possible having a larger OD. This could also cause you to dent your tank.

    R-Dubb had a machinist make 8-10 sets of custom triple clamps to put KTM forks onto GS's or G/S's and solved these issues. He sold 'em for about $650 or something (all gone I believe) and wrote a thread about it as well. There is also a German company that makes a reported "plug and play" triple clamp set for about the same cost...

    http://www.bmwboxersupplies.com/index.php/cPath/7?osCsid=e4aade3f4036daf29fff320281f310c4

    $559 Euro (the owner Mat said he would discount if someone stepped to the plate to become the US distributor for his products...)

    [​IMG]
    #10
  11. crankshaft

    crankshaft Guns are for pussies

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    My Spacer looked almost exactly the same. Pretty simple machining if you have the correct tools. Unfortunately, my buddy no longer has a shop, so I can be of no help.

    Daryls machine shop in Jericho would probably be able to help you though.

    [SIZE=-1]Jericho, VT (Vermont) 05465 Phone: (802) 899-4007 ...

    Daryl made a cailper bracket for me when I did the CR250 forks on the DR.

    I used BMW races with CR250 bearings and everything worked great. Buy a set of DR bearings and see if the have the same taper as the BMW races (which I think they will) then all you need is the spacer and your done.

    [​IMG]

    I sort of miss the bike, but I'm relly hating BMW's at the moment:lol3


    [/SIZE]
    #11
  12. Stagehand

    Stagehand Imperfectionist

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    they all bein faster than you? :lol3




    :hide
    #12
  13. crankshaft

    crankshaft Guns are for pussies

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    I drilled and tapped holes in the CR lower clamp to add new stops with standard bolts, so no tank denting. The DR forks are also thinner than the CR forks and probably thinner than the KTM's.
    #13
  14. crankshaft

    crankshaft Guns are for pussies

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    Only if they run. My X is still at the shop.......
    Never again, I'll ride my peddle bike before I throw a leg over another BMW:lol3
    #14
  15. elmoreman

    elmoreman takin' a break, boss

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    Thanks for the tips, Cranky. I gave the bearings a try, and the bottom bearing on the DR stem has a wider diameter by a couple of mm than the g/s. However, when I flip it over, the bearing is a perfect fit for the race in the top of the tube. So I need to increase the diameter of the DR steering stem by a little on the bottom (with some kind of spacer sleeve, I guess, so that I can get the stock g/s bearing on the top and use the DR bearing on the bottom).

    That sound right? Should I try and get a thin sleeve to put on the stem or perhaps try to slip a DR bearing entirely into the bottom of the g/s (using the outer race of the DR bearing as the spacer), meaning there would be in effect two outer races stacked...Does that make sense?
    #15
  16. elmoreman

    elmoreman takin' a break, boss

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    If anyone is interested in doing this, things just got easier.

    As Crankshaft mentioned, he thought the DR650 bearings would fit, and they will according to Kevin at All Balls Racing:clap . In his words, "Wow...you got lucky." The OD is the same, but the ID is different, which is why the pitch of the bearing taper is different. Pretty simple, actually.

    Kit # 22-10-13 will give you a complete kit that should fit the DR stem in the GS head tube. Now to order the bearings, take out the old races, and start putting it together. I'll place a call to the machine shop later this week for the spacer.
    #16
  17. Stagehand

    Stagehand Imperfectionist

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    I'm interested, and thats HotPants right there :deal

    Sweetness.
    #17
  18. RocketJ

    RocketJ Been here awhile

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    That is some useful info. I wonder if the same is true of the KTM stems.
    OD vs ID/pitch is the problem there, too. Does this bearing have a larger ID, while keeping the same (bmw)OD?
    #18
  19. elmoreman

    elmoreman takin' a break, boss

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    Yes. The ID is larger, though not by much, to accommodate the lardger stem. The OD is the same. If you are looking at a similar modification, I would suggest to call all balls (great name, huh:lol3 ). There are probably others, but I came upon them, and found the guy on the phone (Kevin) to be very helpful and, dare I say, actually interested!
    #19
  20. crankshaft

    crankshaft Guns are for pussies

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    Sweet:clap After staring at the DR forks for months, I always thought they would be a great option for the old g/s. Next up is an undermount:deal

    I hope all the BMW airhead guys are home right now kicking the dog:lol3
    Another shitty front end gets what it deserves..... right in the junk pile:poser
    #20