An Unholy Union II: Wp Extreme 50mm Conventionals on a G/S

Discussion in 'Airheads' started by Solo Lobo, Apr 9, 2011.

  1. Solo Lobo

    Solo Lobo airhead or nothing

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    Stole a few minutes in the garage just now.... the 1999 KTM 640 caliper arrived (eBay purchase) and had some mungged up threads and more crap in there then I have ever seen... tap and die kit to the rescue!

    [​IMG]

    So, in the picture are 2000 640 legs, triples and axle, a 1999 640 caliper, a 1998 125 SX front wheel, and a new 300mm 640 rotor...

    Although you can't tell in this picture, the wheel is spinning for dramatic effect :lol3

    [​IMG]

    Anyone catch the bent spoke ?... I need to go and buy a replacement for that.... In a related note, the upper ear of the caliper mount bracket is making slight contact with the rotor. I think the Braking USA rotors are thicker than stock, but don't know for sure. I either need to shim the caliper mount bracket or grind a bit of it off. Don't know which I am going to pick yet.

    Next up, stripping the fork legs and shortening the travel... with no permanent negative effects!
    #41
  2. Solo Lobo

    Solo Lobo airhead or nothing

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    Update coming shortly.... have one fork partially stripped and am trying to overcome not having a adjustable pin spanner right now. Once I tackle this bit the next challenge will be finding the correct ID/OD material to use on the rebound side as a travel limiter... need to finish the strip to determine what dim's are needed.

    Also have a line on a local KTM front wheel that looks much nicer than mine.
    #42
  3. Solo Lobo

    Solo Lobo airhead or nothing

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    OK, Let's get busy with the fork strip... this is all done following the instructions from the Husaberg WP Extreme manual linked on the first page.

    Remove the top:

    [​IMG]

    Here are the innards, the black plastic tube is a 3.5" spacer that I will be removing from the comp side, and replacing with a different spacer on the rebound side to limit the fully extended length. This will be a temporary measure to make the forks similar in length to the stop forks until I extend the swing arm and go back to full length. I haven't made any calculation and haven't planned on changing the springs and valving... I will only be shortening the length to do some testing.

    [​IMG]

    And the correct order and orientation of those bits:

    [​IMG]

    610 mL's drained from the tube:

    [​IMG]

    Oops, the lower washer that is below the spring fell out while draining the forks the manual is very specific that the orientation of this washer should be carefully noted!

    [​IMG]

    So here are all the bits:

    [​IMG]

    Next, remove the lower bolt to release the damper. I used the axle to hold the leg while removing the bolt.

    [​IMG]

    Extract the damper mechanism

    [​IMG]

    See that aluminum wheel at the top? It has to be unthreaded to allow access to the return spring where the new extension limiting spacer is going to go... the manual shows this fancy tool that I don't have and am not going to buy.

    The first attempt to make a adjustable pin spanner involved an old crescent wrench and two drill bits, stolen from last month's Classic Bike magazine:

    [​IMG]

    [​IMG]

    After dulling and sharpening a number of bits, a number of times and not making any headway (use, I used copious oil to cool the bit) I changed it up and used an old rear shock spanner

    [​IMG]

    That quickly bent

    [​IMG]

    I didn't want to clamp the tube in the vice, so here is what I did, I ended up using another c-clamp on the other end of the screwdriver with a small block of wood to hold everything in place

    [​IMG]

    Version three... another shock spanner, but twice as thick as the version 2 version

    [​IMG]

    That with some heat did the trick! The spacer is going to go below that spring and will reduce to total length the forks can extend to.

    [​IMG]

    So, now I need two sections of tube that have an OD less than 21mm (edit - 20.0mm to 20.3mm fits well, closer to 21mm does not) and an ID larger than 12mm. The closest thing I could find at the local hardware store is 1/2" schedule 40 pipe. It is a starting ID of ~15.3mm and an OD of ~21.4mm

    [​IMG]

    Now, I am trying to figure out the easiest way to turn down the OD of the schd 40 to 21mm without a lathe.... more later need to eat some lunch.
    #43
  4. Solo Lobo

    Solo Lobo airhead or nothing

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    Problem solved... a nut, a few washers, a long bolt, an allen key, a socket, socket wrench, open-end wrench, drill, strap wrench and a few c-clamps later.....

    the rig:

    [​IMG]

    [​IMG]

    In action:

    [​IMG]

    Results:

    [​IMG]

    It was a bit wobbly, but it worked. The OD isn't consistent over the length but it doesn't need to do anything other than fit inside the outer damper tube and move easily within (no binding).

    Off to make another for the other fork leg now
    #44
  5. bgoodsoil

    bgoodsoil Dare to be Stupid

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    [​IMG]

    I love it! :clap That's some New Yankee Workshop stuff right there.
    #45
  6. Solo Lobo

    Solo Lobo airhead or nothing

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    Thanks Brad :D

    I just went back and had to turn both spacers down to about 20.1-20.3mm to make them a nice fit in the damper tube... setting up the socket as the "live center" (is that correct nomenclature?) the second time was a PITA :lol3

    [​IMG]
    #46
  7. Lornce

    Lornce Lost In Place

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    Solo, Love your lathe. :rofl Pretty is as pretty does, dude. :thumb

    Haven't read the whole thread, but briefly can you tell me why folks are so anxious to swap the original triple clamps on all these conversions? :scratch

    Is the trail dimension increased beyond what is usable with original trees at airhead steering rake specs?


    :ear
    #47
  8. Solo Lobo

    Solo Lobo airhead or nothing

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    :D


    My first test is going to use the stock triples (KTM that is) and see how it works... Marcus Best liked the R-Dubb triples with shortened Extremes until he changed to an HPN frame and extended swing arm in S. Africa (via Dustdevil). He mentioned in another thread that he thought the longer swinger changed the handling to the negative, and using the shorter off-set KTM clamps may return the handling. I am afraid I haven't studied up enough on the subject yet to comment.... but will at some point.
    #48
  9. Solo Lobo

    Solo Lobo airhead or nothing

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    With the inner damper rod removed, you invert the rod and unscrew the "tap rod" from the "piston rod". As usual, I didn't have the fancy WP vice jaws that lightly by firmly hold the piston rod without marring it, so I improvised...

    [​IMG]

    The spring was a tight fit, and I had to wiggle it off while gripping it with pliers

    [​IMG]

    Here is the new travel-limiting spacer installed, spring and "tap rod" re-installed (if i can find an appropriated size washer, I will put one between the spacer and spring)

    [​IMG]

    Below is the end result, shortened on the left, stock on the right (obviously)... The shortened one has no oil yet (forgot to buy some :lol3)

    [​IMG]

    I removed a 3.5" spacer on the comp side and installed a 3.75" spacer on the rebound side. A few years ago I had a set of shortened WP Extreme's that I sold to roadsacallin' who rode around the world with 'em... I can't remember what their total length was, but they were almost identical to an R100GS's overall fork length... 3.75 was just a guess on my part for these no math was involved :evil This added a bit of more preload then I started with as re-installing the top nut took a bit more force to get done (pushing down on the cap nut while pulling up on the tube) hence the >3.75" end result

    [​IMG]

    Total length of the shortened side, from approximately the middle of the axle

    [​IMG]

    Same measurement on the stock forks of my G/S

    [​IMG]

    Yesterday my new Acerbis Baja fender arrived for this front end (thanks Simonpig!)

    [​IMG]

    Thanks enough for today, it's beer o'clock for me :thumb
    #49
  10. Stagehand

    Stagehand Imperfectionist

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    :bow :freaky
    #50
  11. simonpig

    simonpig droppin' jewels

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    Just caught this thread. I see why you want the fender now. Going all HPN on us. :clap Subscribed.
    #51
  12. Lornce

    Lornce Lost In Place

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    Solo, genuinely curious:

    You have the overlength swingarm, which cause me to suppose you're going to raise the rear of the bike. :ear

    Why are you shortening the front end if you plan to use it in conjunction with a raised rear?

    :ear


    Please don't say I have to go back and read the whole thing... :D

    :rofl

    :thumb
    #52
  13. Solo Lobo

    Solo Lobo airhead or nothing

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    My plan is to fit the front end ASAP, in the shortened length and ride for the summer. The extended swinger is going to take some time and some cash to complete... so it is a fall/winter project. The frame may also need to be strengthened for the front and rear mods.

    Pulling the forks apart again to re-extend them is perhaps a hour or two's labor at worst, and I have to admit I do like wrenching as much as riding so no down side for me there.

    I am still deciding if I want to go all HPN on the frame (big $$$, long wait), or Paul Rooney (don't know much yet about that option) or something else. I am considering if I really want to mod my stock '81 frame, or do something else... I am a bit of a purist and don't want to trash my bike (nothing against you Brad :D)... lots to consider here.
    #53
  14. Lornce

    Lornce Lost In Place

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    Oh, I see.

    Sorry to interrupt.

    :wave
    #54
  15. bgoodsoil

    bgoodsoil Dare to be Stupid

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    I've got an excuse for not calling Paul Rooney this time! I trashed my bike :D
    #55
  16. Lornce

    Lornce Lost In Place

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    Whod'ja do?


    :ear
    #56
  17. bgoodsoil

    bgoodsoil Dare to be Stupid

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    the pin holding in my main bearing fell out and blocked an oil passage. I got a new engine in and fired it up today. It's been a loooong week.
    #57
  18. Lornce

    Lornce Lost In Place

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    That's got to be fairly uncommon. :huh

    Thankfully.

    :thumb
    #58
  19. bgoodsoil

    bgoodsoil Dare to be Stupid

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    Snobum said it's RARE. And you know he wouldn't put it in all caps, big fonted and yellow for nothing :D

    Dean said he's seen it happen several times and so did David Woodburn. I don't know if the way I ride the bike contributed or not. I guess if I ride this engine in the same way and knock another pin loose I'd be safe in assuming 'yes' :lol3
    #59
  20. ontic

    ontic

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    Great update!
    I've been going into withdrawals here. I've run out of WP50 related stuff to read and my WP50 front end seller seems to have gone on holiday before he worked out postage to me:cry:lol3

    Interesting you'd be considering Paul Rooney. Has anyone ever mentioned the cost for him to reinforce a frame? I like to know. I thought I read somewhere that he used to be able to sell a reinforcement/gusset kit? Something else I'd be interested in.
    My parts guy often sells frames to Paul, GS mainly I think. I might have to put a few feelers out.

    about frame reinforcements, I'm in a similar thought process. I doubt I will do it. I too don't want to screw with my bike too much. I probably won't need it reinforced, but the temptation is there to do it right the first time. I am completely undecided yet. My bike aint matching numbers, so I don't think there is much point being too puritanical.

    I love your Poormans Lathe. I used to do the exact same thing. I've even turned up metal with set-ups like that (it gets interesting when you use your set up turning metal and then an angle grinder instead of a chisel:deal). Now I've got a funny old lathe that someone took the time to hand make, that I mainly use to do all my polishing. It's set up outside the shed with a tarp over it... forgot the tarp the other week, it rained, the power was on, and something has shorted. Bugger. Might have a look at that today.

    Looking forward to the next update,
    Cheers,
    #60