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Old 02-06-2012, 10:49 AM   #1
JPSpen OP
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91 R100GS Front End Refresh

One of the fork seals started puking on my GS... So it's time to go in and do a refresh.....

I'd like to upgrade it a little...Not interested in replacing the forks but possibly doing some mods to the stock front end..

Suggestions ? I'm sure I'll upgrade the fork springs and maybe do something with the valving...

Looking for input... I don't have a ton of money to spend on this but don't want to waste the opportunity to beef her up a little so that I can take it on the TAT sometime..Just really want to know what works and what doesn't with the stock forks..

Thanks

John
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Old 02-06-2012, 11:53 AM   #2
Boojum
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I've NOT done it yet, but I have ordered stiffer fork springs, and will add the racetech gold valve, with a fluid change in the coming week or two. I'm in hopes of adding some much needed life in my stock front forks.


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Old 02-06-2012, 12:50 PM   #3
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Quote:
Originally Posted by JPSpen View Post
One of the fork seals started puking on my GS... So it's time to go in and do a refresh.....

I'd like to upgrade it a little...Not interested in replacing the forks but possibly doing some mods to the stock front end..

Suggestions ? I'm sure I'll upgrade the fork springs and maybe do something with the valving...

Looking for input... I don't have a ton of money to spend on this but don't want to waste the opportunity to beef her up a little so that I can take it on the TAT sometime..Just really want to know what works and what doesn't with the stock forks..

Thanks

John
I have Works springs in my GS with 10 and 15 wt oil. I'm actually quite happy with the results. I do not ride dirt but on the street (canyons) it feels compliant but tractable. FWIW, I also tend to ride at a pretty quick pace and only when really pushed hard, do I get that vague un-planted feeling. I have done the Racetech conversion in my R75/5 race bike and am thrilled with the results for its intended purpose. It all comes down to how you intend to ride the bike. I have not ridden an RT set up on a GS but think it might be overkill based on my experience with the R75. High bars and a skinny front make for a vague front end, RT claims to be better at both slow and fast damping, I only see it helping the fast damping which would make the GS unpleasant for most of my saddle time.
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Old 02-06-2012, 12:59 PM   #4
Rapid Dog
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Note that your GS will take 1/2 a RaceTech gold valve kit.
One side is compression. Find a buddy to split a kit with...

http://www.rapiddog.net/BLOG/FORK%20IT.htm
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Old 02-06-2012, 02:26 PM   #5
supershaft
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Don't forget what your else your forks might need besides the seal. Chances are they need new bushings! That's a good chunk of change right there since they have recently really gone up in price.
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Old 02-06-2012, 06:33 PM   #6
Steve G.
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I bought my '91 GS Bumblebee new in July '91, after 120,000 kms.. Only last fall did I decide to try something different with the suspension. A set of Progressive $80 fronk springs has offered me a view of how bad the original springs really were, so muich so that I will definitely upgrade the rear shock with a Progreessive unit this spring. It really is the best $80 I've spent on this bike since I bought it.

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Old 02-06-2012, 08:57 PM   #7
One Less Harley
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progressive springs are not recommended w/ Race tech Gold valves.
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Old 02-07-2012, 07:47 AM   #8
Rapid Dog
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... Race Tech springs can be recommended by Matt Wiley if you contact him at Race Tech.
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Old 02-07-2012, 10:14 AM   #9
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contact me if you want a half a set of Racetech valves...
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Old 02-07-2012, 06:12 PM   #10
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RT valves

Quote:
Originally Posted by camgregus View Post
contact me if you want a half a set of Racetech valves...
PM sent.

JZed
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Old 02-07-2012, 07:39 PM   #11
JPSpen OP
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Ha! Beat to the punch by jzed on my own post..
That's cool though as I'm thinking of doing the Progressive springs and a little heavier oil.

I'll do the seals, bushings, dust covers and upgrade the springs. I'm not looking to build a race bike, just one that won't fall apart if I get it off the highway.

I've already got a Works shock on the back and some TKC 80's on it as well.

Thanks for the input. I'll take pics and do a writeup of the rebuild.


John
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'03 BMW R1200CLC "Flipper"(Tis but a scratch!)
'01 BMW R1100RT "Lucky"
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Old 02-10-2012, 07:03 PM   #12
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Please read the Old's Cool rule before posting.

Thank you,

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Who just had to move your thread.
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Old 02-10-2012, 10:24 PM   #13
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A cheap way to experiment is with your forks is oil viscosity & volume. Heavier oil will firm up the ride, good on pavement. Lighter with an ounce more oil will be better on gravel. Easy to do, easy to change. I adjust mine depending on what type of riding I do. I use 12.5w (50/50 10w & 15w) for pavement, 10w when doing significant backroads.

Lots of theories out there if you want to Google "motorcycle fork oil adjustments"
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Old 02-10-2012, 10:52 PM   #14
supershaft
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The whole point of GS forks is to run different weight oil in each side. Personally I could see running 5 weight in the compression side and 25 weight in the rebound side but that is just me.
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Old 02-11-2012, 02:49 AM   #15
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I have just emailed my friend (and mechanic) who is an absolute wiz on airheads. He services and rebuilds only BMW`s and loves the air cooled twins. He made a turbo charged fuel injected R90 S many years ago which is bullet proof and currently is finishing a monoshock R65 w/- 1070cc kit, fuel injection K front end and countless other little touches. His next special is for me, an R100Gs based bike and he wants to build up an extended length twin shock swingarm. He knows what he is talking about.

This is what he recommends you do to refresh the front end.

Drain the fork oil by removing the big bolt at the bottom of the forks as well as the drain plug.

Refill with 10wt of fork oil at 470 millilitres per side.

Do one side at a time.

He finds that this is the best for general riding, but if you are doing lots of very rough stuff, fill with a 50/50 mix of 5 wt and 10 wt oil. That`s it. He`s also been happy using standard springs.

I`m guessing you should replace any renewable rubber bits inside the forks while you`re at it.
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