Shorten WP43 Fork for the R80 Project

Discussion in 'Airheads' started by R-dubb, Mar 3, 2013.

  1. R-dubb

    R-dubb Dubbious Adventurer

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    My R80G/S project has finally kicked into high gear with arrival of a brand new YSS shock from Klaus at EPM Performance.

    [​IMG]

    I thought I post a quick how it's done for the fork shortening. I wanted to wait unitl the shock arrived, and then take some educated guesses as to leveling the front. I had the new shock set up at a length of 375mm. This is as far as I dare take the mono swing arm. As I recall (say what), the oem shock is 360mm long. (No, not as I recall, as Wrangler aptly states below)

    Up front, I'm going to look for about 210mm of fork travel. To do that, I need to shorten the WP with a 65mm spacer. We'll see how it all works. If it's wrong, I'll do it again.

    Here are the forks taking shape inside a shiny pair of R-dubb triple clamps:

    [​IMG]

    [​IMG]

    Not a lot of photos, but here's the step by step of getting to that spot right above the top out spring where the 65mm spacer goes. As some of you may know, getting to the spot requires taking the fork legs completely apart including the cartridge.

    1. Remove top cap from slider and drain oil.
    2. Insert thin 22mm open end above fork spring and unwind cap from center rod.
    3. Remove shims and spring then drain more oil by pumping cartridge.
    4. Remove dust seal and snap ring from bottom end of slider and pop stanchion with seals out of slider.
    5. Remove bottom shim stack plug from slider very carefully, using 6-sided 19mm socket on impact wrench. Too much impact, you wreck the nut. Too little and the assembly may spin.
    6. Place cartidge in pipe vice with a protective rag. Heat aluminum tube just below spring collar with torch to melt locktite. Now unscrew spring collar from cartridge tube with 22mm open end.
    7. Voilà, inner rod may now be unscrewed and 65mm spacer of 1/2" Schedule 40 aluminum tubing placed just above top out spring.

    Just in case you don't know how to put it all back, I'm not tellin'. :lol3

    [​IMG]
    #1
  2. Airhead Wrangler

    Airhead Wrangler Long timer

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    Say wha? :huh

    Stock shock length of a G/S is ~360mm. You're not talking stroke length either cuz that'd be way too long. Which measurement are you talking about here?
    #2
  3. R-dubb

    R-dubb Dubbious Adventurer

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    Sorry dude, you know how this metric shit is. Let me fix that pile. :eek1
    #3
  4. Airhead Wrangler

    Airhead Wrangler Long timer

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    I'm curious about the choice of forks. Why the 4354s? I know zero about them, but the pieces look pretty much the same as the 4860s just a little skinnier. Do they somehow manage to avoid the stiction issues that the 4860s have?
    #4
  5. R-dubb

    R-dubb Dubbious Adventurer

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    Has everything to do with the clamps. I made clamps for the 43's whenever that was because they were cheap and plentiful at the time. 48's weigh more and use to cost more used and were scarce due to being newer. I still feel 48's are overkill for our rubber-ish frames.

    43's, they still stick, but maybe a tad less. Same design as 48's. I think they stick more with shallow rake (like airheads). Oh well. Could have used the Extremes. They are buttery smooth, but way heavy. One way to minimize stiction might be less preload and minimal compression damping. I'll let you know how it goes when this thing hits the road in a month or so.
    #5
  6. Phreaky Phil

    Phreaky Phil Long timer

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    I had shortened 43s on my GS and thought they were pretty good. You may find them better shortened as they have more overlap so should stick less.
    #6
  7. Airhead Wrangler

    Airhead Wrangler Long timer

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    Prutser said that additional overlap after shortening helped quite a bit on his 48s.
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  8. Solo Lobo

    Solo Lobo airhead or nothing

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    Good to see you around here again R-Dubb!

    Can you post a few more pix of your headlight bucket support and how it mounts to your triples please?

    [​IMG]
    #8
  9. igormortis

    igormortis Cafe Reise

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    Yes please!
    #9
  10. Ras Thurlo

    Ras Thurlo Desert Lion

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    how bad is the stiction on the 4860s?

    I have them on my '11 EXC and never felt any issues
    #10
  11. Airhead Wrangler

    Airhead Wrangler Long timer

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    Mine are particularly bad, but that's just because I bought them used on ebay and put them straight on my bike without even changing the oil. They cleaerly are in need of a full rebuild. That said, the other 4860s I've seen have more stiction than conventional forks, but I don't really notice much when riding them. The improvement in stiffness and overall function is so much better (on forks in good condition) that I don't really care about a bit of stiction when fully extended.
    #11
  12. Ras Thurlo

    Ras Thurlo Desert Lion

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    is there that much performance gap between USDs and conventionals?
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  13. Airhead Wrangler

    Airhead Wrangler Long timer

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    Depends which ones you're talking about. The layout, USD or conventional, has a lot less bearing on performance than the internals, though typically USD forks are less flexy and have lower unsprung weight than comparable conventionals. Modern conventionals with adjustable compression and rebound damping and a tunable shim stack (aka open cartridge forks) are every bit as good performance-wise, but most conventional dirt bike forks are so-called damping rod (more accurately "fixed orifice") forks. They are comparatively primitive and their performance isn't nearly as good. Think KLR650 vs. 690 Enduro.
    #13
  14. Ras Thurlo

    Ras Thurlo Desert Lion

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    so assuming we are using good conventionals, the argument comes down to relative unsprung weight

    Optically you would think there is a bunch of difference, is this the case?

    How much can that difference be felt in practice?
    #14
  15. Airhead Wrangler

    Airhead Wrangler Long timer

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  16. Ras Thurlo

    Ras Thurlo Desert Lion

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    I get both points of view
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  17. Airhead Wrangler

    Airhead Wrangler Long timer

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    One more pro for conventionals is that you can use fork boots on them and thus oil seals tend to last quite a bit longer.
    #17
  18. ontic

    ontic

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    Is that the only reason for some USD's having a tendency to blow oil seals, I thought it was something a little more inherent to the design than dust/dirt/chip damage (ie oil always sitting above seals)?

    Another pro for conventionals is the ability to use fork braces.

    Parts availability for our 5060's though... :cry
    #18
  19. R-dubb

    R-dubb Dubbious Adventurer

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    [​IMG]

    Uses two interconnecting aluminium angles. Cut out most of the top flange on each.

    Two holes into voids behind front of top triple, with 6mm socket heads and nuts behind. Two more bolts through front angle into oem rubber grommets on headlight shell. Then there are two bolts through the top tabs to connect the two angles in the middle, making it possible to detach. First photo in top post was too wide at the top for cables and such. This one is what it looks like now. I cut the top flanges down to 50mm wide in center and moved them very close together to keep shell tight to the clamps. Made the turn signal stalks, welded to a flat bar and bolted it to the front flange all the way across the bottom. Nothing touches, but it's close.

    [​IMG]

    Bottom of shell uses a single bolt inside a spacer to a little tab and a threaded bolt hole into center of lower clamp. Pretty simple stuff.

    You're all getting ahead of me. I'll post a short build thread sometime soon :deal
    #19
  20. chipsdad

    chipsdad Adventurer

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    used to race mountainbikes with usd forks. the aluminum ones stuck like hell. tolerances are really tight and over clamping the tubes is a major potential for issues. I know for a while the mechanics were crazy glueing the interface and doing the bolts little more then finger tight to get by. also the lack of a lowerbrace causes lots of twisting, which prevents the stansions from traveling freely. they look cool though, i'd run em.
    #20