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Old 03-03-2013, 07:58 PM   #1
R-dubb OP
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Shorten WP43 Fork for the R80 Project

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



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:





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'.


R-dubb screwed with this post 03-03-2013 at 10:29 PM
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Old 03-03-2013, 08:06 PM   #2
Airhead Wrangler
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Quote:
Originally Posted by R-dubb View Post
I had the new shock set up at a length of 175mm. this is as far as I dare take the mono swing arm. As I recall, the oem shock is 168mm long. Just 7mm in shock length compounds into more like 12mm of additional travel triangulated.
Say wha?

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?
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Old 03-03-2013, 08:16 PM   #3
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Quote:
Originally Posted by Airhead Wrangler View Post
Say wha?

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?
Sorry dude, you know how this metric shit is. Let me fix that pile.
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Old 03-03-2013, 11:01 PM   #4
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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?
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Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
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Old 03-03-2013, 11:29 PM   #5
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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.
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Old 03-04-2013, 12:41 AM   #6
Phreaky Phil
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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.
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Old 03-04-2013, 07:06 AM   #7
Airhead Wrangler
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Quote:
Originally Posted by Phreaky Phil View Post
You may find them better shortened as they have more overlap so should stick less.
Prutser said that additional overlap after shortening helped quite a bit on his 48s.
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Old 03-04-2013, 09:14 AM   #8
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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?

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your bike is suitably dirty. Well done.
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Old 03-04-2013, 12:13 PM   #9
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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?
Yes please!
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Old 03-04-2013, 03:10 PM   #10
Ras Thurlo
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Quote:
Originally Posted by Airhead Wrangler View Post
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?
how bad is the stiction on the 4860s?

I have them on my '11 EXC and never felt any issues
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Old 03-04-2013, 03:14 PM   #11
Airhead Wrangler
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Originally Posted by Ras Thurlo View Post
how bad is the stiction on the 4860s?
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.
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R80ST Gets The HPN Treatment
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Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
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Old 03-04-2013, 03:24 PM   #12
Ras Thurlo
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Quote:
Originally Posted by Airhead Wrangler View Post
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.
is there that much performance gap between USDs and conventionals?
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Old 03-04-2013, 03:32 PM   #13
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Quote:
Originally Posted by Ras Thurlo View Post
is there that much performance gap between USDs and conventionals?
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.
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R80ST Gets The HPN Treatment
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Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.
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Old 03-04-2013, 03:47 PM   #14
Ras Thurlo
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Quote:
Originally Posted by Airhead Wrangler View Post
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
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?
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Old 03-04-2013, 03:52 PM   #15
Airhead Wrangler
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[QUOTE=Ras Thurlo;20864472]so assuming we are using good conventionals, the argument come down to relative unsprung weight



Unsprung weight and stiffness. USD forks are just a "better" design when you consider the forces acting on the forks.

Quote:
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Optically you would think there is a bunch of difference, is this the case?
Well yeah. Definitely. Some people think airheads are supposed to have conventionals. I agree that they look better on an older bike, but I'd rather put performance and parts availability ahead of aesthetics. Shiny part up or shiny part down? That's the question.
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Current rides: HPN #834, '93 R100GSPD "red rocket", '73 R75/5 Toaster mongrel, '80 Ducati Pantah 500SL, '92 DR350, '67 Honda SS50, '80 Honda Chaly.

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