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Old 05-21-2009, 09:22 AM   #166
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I dont know if I mentioned, but the GV for the GS has me totally confused
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Old 05-21-2009, 11:16 AM   #167
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Just a note - a lot of you probably already know this though. If you're planning to run a bottle of techron through your tank, be sure to do it toward the end of an oil change interval. I didn't really think about it and did it with fresh oil. My nice clean oil turned dark pretty quickly.
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Old 05-21-2009, 11:33 AM   #168
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Quote:
Originally Posted by Airhead Wrangler
So will the Gold valve be providing all of the compression damping in your setup? It seems to me that the gold valve was not designed to provide any compression damping, but rather act as a bypass valve for fork oil to bypass the stock compression damping in order to allow faster fork movements on sharper bumps. It may work in this usage, but I don't think it was designed to provide any compression damping on its own. I'm interested to see how this turns out.
If you read the articles on the Gold Valve it is clear that the Gold Valve takes over the compression damping, emulating the type of progressive damping you only find in cartridge type forks like for instance WP USD forks.
They do not do rebound damping.
The advantage of the Gold Valve over stock damping rod suspensions is that the Gold Valve can allow more oil to flow through if need be like in the case of hitting a pavement at high speed. It will however also prevent the fork to bottom out because as the fork is compressed, the higher pressure from the fork spring being compressed will start to restrict the flow of oil through the Gold Valve nearing the end of the fork travel.
So the Gold Valve will allow more unrestricted flow of oil in the initial movement of the fork if it is a high speed movement but it will start to restrict this flow nearing the end of the fork travel to prevent bottoming of the forks.
The next advantage is that they are adjustable and can be custom tuned to rider preference and motorcycle type. This is not possible on the move but it is far better than the factory setup which you will have to live with on the stock setup on damping rod systems. This is nowhere more applicable than with the GS as this bike is mostly intended to be used on paved road surfaces and more than half of GS owners never take their bikes on dirt roads never-mind off-road. You can see why the para-lever GS's handle great on tar but not so great when the road surface start getting more rough. The Gold valve will allow you to get a good setup for either fast road use or heavy off-road. No suspension will provide the ideal setup on both sides within one adjustment setup, so it is important to decide what is most important for you and then set it up accordingly.
Road use normally require a firmer setup with a slow rebound where off-road you might want the shock to respond a bit faster when hitting large bumps but it must still be firm enough to prevent bottoming. Rebound should normally recover fast but not too fast so that the wheel start bouncing of the road surface.

Rebound is adjusted with the weight of the fork oil used and compression with spring-tension. (heavier spring or the tension applied to the spring with the adjuster.)

This is all just theory for now but soon I will be able to report here what the final theses is.
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Old 05-21-2009, 11:48 AM   #169
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hey, where does a fork brace land in all this?
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Old 05-21-2009, 03:33 PM   #170
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Quote:
Originally Posted by Dustdevill
Airhead Wranglers ST fitted with the forks from a 100GS is the best combination.
I keep pondering this, Dustdevil, and so would you please elaborate... isn't the ST mostly an R80 GS with R65 front fork assembly/less suspension travel. Is there something more... less weight than R100GS perhaps... that makes it the best combination

Mostly I'm curious as I'd like to turn my ST a little more dirt-capable. Also Airrangler has the R100GS rear subframe which I imagine should be done in conjunction with the front forks... both sound like great modifications.

Also... how best to lighten the bike?
(Can't imagine much can be lost)
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Old 05-21-2009, 05:59 PM   #171
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Quote:
Originally Posted by Renner
I keep pondering this, Dustdevil, and so would you please elaborate... isn't the ST mostly an R80 GS with R65 front fork assembly/less suspension travel. Is there something more... less weight than R100GS perhaps... that makes it the best combination

Mostly I'm curious as I'd like to turn my ST a little more dirt-capable. Also Airrangler has the R100GS rear subframe which I imagine should be done in conjunction with the front forks... both sound like great modifications.

Also... how best to lighten the bike?
(Can't imagine much can be lost)
Close but not quite the same. The forks are "similar" to R65 forks, but apparently still longer. I have some R65 forks in the garage and the lowers are the same part number, but they are still much shorter than the ST forks.

As an interesting sidenote, when I compared the published specs for suspension travel between my 99 F 650 and my 83 R80 ST, they are so close as to be the same for all practical purposes. So the ST still retains a good bit of latent dual sport potential along with its very good street manners (something the F650 also has).
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Old 05-22-2009, 09:51 AM   #172
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Quote:
Originally Posted by Renner
I keep pondering this, Dustdevil, and so would you please elaborate... isn't the ST mostly an R80 GS with R65 front fork assembly/less suspension travel. Is there something more... less weight than R100GS perhaps... that makes it the best combination

Mostly I'm curious as I'd like to turn my ST a little more dirt-capable. Also Airrangler has the R100GS rear subframe which I imagine should be done in conjunction with the front forks... both sound like great modifications.

Also... how best to lighten the bike?
(Can't imagine much can be lost)
By best combination I am referring to the Monolever swing-arm and R100-80GS forks by Marzocchi. ST or G/S it does not matter. You will have to fit a longer rear shock to the ST and the centre stand might also need replacing. To keep the same geometry of the G/S with standard fork you will have to drop the forks in the triple clamps by 15 mm. This will require a different indicator mounting setup.
The Para-lever suspension is proven to give a very sporty response with the low weight of the aluminum casing but not in the case of the R80-100GS as the angle of the shock is almost parallel to the swing-arm. This cause the bottom mounting point to move up and down with very little compression of the shock.
HPN does a very nice conversion of the Paralever GS's by installing the swing-arm of the 1100GS or 1150GS. This is the ultimate but plenty of Dollars needed.
As far as the airhead GS's go the Monolever is king, both in it's simplicity and reliability as well as it's performance when fitted with a good off-road shock.
The forks fitted to the G/S are real crap though and worse is the fact that they were designed for the RS and RT's and only slightly adapted for off-road use.
The 36mm diameter of the forks and the flimsy top yoke made from 3mm plate makes these very flexable and when they flex to much it adds friction that interfere with the up and down movement of the forks resulting in a harsh response.
The Marzocchi's on the other hand was designed for off-road use and as far as damping rod forks are concerned probably the best you will find. In the standard setup they are more than capable and although I would often bottom the stock rear shock on the models I've owned in the past I can't recall the front bottoming that easy. The Gold Valve is still to be proven as an improvement to myself. My own preference is the Sport damping kit sold by HPN and maybe even some dealers if still available. BMW part number can be found under forks (31) on the parts catalogue for the R80GS Basic.
This damping kit change the mechanism from a damping rod to cartridge type setup that is adjustable for both rebound and compression damping.
Front wheel and brakes is also much better.
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Old 05-23-2009, 07:23 AM   #173
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great information, all of which is new to me, thanks.

So where do the R100GS forks and the ST interface: same steering yoke spindle size? And is the R100GS top clamp adequate?

AirheadWrangler? Anyone?

Reading back through your thread here AW, they seem to have hopped on your bike around page six.
Was it that simple?
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Old 05-23-2009, 10:05 AM   #174
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Quote:
Originally Posted by Dustdevill
By best combination I am referring to the Monolever swing-arm and R100-80GS forks by Marzocchi.
+1.

I built a bike with exactly that configuration and was more than happy with the outcome, in every respect.

My R100G/S (click for higher resolution)

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Old 05-23-2009, 04:26 PM   #175
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Very Nice!!!!
It is however a lot easier and cheaper to start with a Monolever model and add the R100GS front end than the other way around off-coarse.
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Old 05-23-2009, 04:30 PM   #176
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Quote:
Originally Posted by Renner
great information, all of which is new to me, thanks.

So where do the R100GS forks and the ST interface: same steering yoke spindle size? And is the R100GS top clamp adequate?

AirheadWrangler? Anyone?

Reading back through your thread here AW, they seem to have hopped on your bike around page six.
Was it that simple?
The frames are identical in the steering head area and both fork setups can be transfered to the other frame with no problems. The top clamp might not be the best out there but it is 100% better than the flimsy 4mm plate of the R80G/S.
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Old 05-23-2009, 05:22 PM   #177
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Quote:
Originally Posted by Dustdevill
Very Nice!!!!
It is however a lot easier and cheaper to start with a Monolever model and add the R100GS front end than the other way around off-coarse.
That idea never crossed my mind Where's the fun in that?

Besides, the real reason for using the 4-lug monolever was to have more choice of final drive ratios: 37/11, 32/10 and 33/11.
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Old 05-23-2009, 06:01 PM   #178
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dang that bike's ugly.....I like it!
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Old 05-24-2009, 12:02 AM   #179
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I have used the 37/11 final drive straight of the R80G/S on my HPN fitted with the brutal Mahle 1043cc conversion in combination with a taller 5th and shorter 1st. Max speed is 180km/h although I have only done 170km/h. Max speed is not the issue here though, When you fit tall suspension with huge static sag it is not a good idea to go flying around at high speeds on the highway.
But boy... when you open her up in 1st, 2nd, 3rd and even in 4th the response is devilish and I would easily compare the power at the back to that of the HP2 producing almost 25 more horses than the Mahle motor.
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Old 05-24-2009, 12:12 AM   #180
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Quote:
Originally Posted by StephenB
That idea never crossed my mind Where's the fun in that?

Besides, the real reason for using the 4-lug monolever was to have more choice of final drive ratios: 37/11, 32/10 and 33/11.
I have often wondered if the R80-100GS rear wheel will fit on the 4-lug hubs and what brakes will work. Did you fit your GS back wheel? All the bikes using the 4-lug hubs were fitted with mag wheels.
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