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Old 03-20-2011, 11:31 AM   #1
C5! OP
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Fork oil capacity and viscosity

A question for one who has a manual, what is the fluid capacity of each of the fork leg of the F8GS, and what viscosity is recommended in the manual??
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Old 03-20-2011, 11:50 AM   #2
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I'm fairly certain the stock is 7.5 weight oil.

If starting fresh you'll need almost a quart for each fork, the correct amount isn't determined by volume, it's determined by measurement.


60 mm from the top, spacer installed, fork fully compressed. Or was that with spring installed....? maybe someone can confirm....


you need one of these to correctly measure fork oil.


http://www.motionpro.com/motorcycle/partno/08-0121/



On ebay you can get a service manual for cheap from a Canadian seller who ships worldwide.


cheers
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Old 03-20-2011, 12:17 PM   #3
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Spring removed, spacer and spring guide left in: If you are cheap like me get a turkey baster, mark off 60mm from the sucky end, hold it with the mark even with the outside slider and draw out the excess.
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Old 03-20-2011, 12:29 PM   #4
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Quote:
Originally Posted by itsatdm View Post
get a turkey baster, mark off 60mm from the sucky end, hold it with the mark even with the outside slider and draw out the excess.


good idea!

And I thought I was smart....
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Old 03-20-2011, 10:16 PM   #5
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Quote:
Originally Posted by ChiTown View Post
good idea!

Mityvac with a zip tie on the tube also works.
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Old 03-21-2011, 09:36 AM   #6
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Quote:
Originally Posted by itsatdm View Post
Spring removed, spacer and spring guide left in: If you are cheap like me get a turkey baster, mark off 60mm from the sucky end, hold it with the mark even with the outside slider and draw out the excess.
Took me a minute to get how that would work. You don't mean 60mm of fluid inside the turkey baster.... you mean 60mm from the tip up the side and then draw a line on it.

You mean a turkey baster like this one:


I tend to like having one like this in the kitchen instead. Not sure it'd be as useful trying to figure out what 60mm looks like tho...
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Old 03-21-2011, 09:39 AM   #7
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Uh...That's a whole lot more than 60mm's.
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Old 03-21-2011, 10:49 AM   #8
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Quote:
Originally Posted by C5! View Post
A question for one who has a manual, what is the fluid capacity of each of the fork leg of the F8GS, and what viscosity is recommended in the manual??
First, there is no right answer.

Second, suspension fluid weight isn't really controlled by a standard (like motor oil) so unless you find a relative chart (googles PVD designs) you don't know exactly what you're getting. It's mostly relative, but there's a few out of family exceptions.

For a bone stock suspension, something in the "normal" 7.5-10w range will work best. Measure using ingenuity. I jus use a zip tie or a half inch wide scale, then pour in/out as required. A small discrepancy between forks will have zero effect on suspension action so don't worry about being crazy exact. Within a mm or two is fine. Make sure you pump the damper to get all the air out first.

For oil height, I'm currently using about a 120mm air gap. Makes the suspension less stiff deep in the stroke. Seems to work okay for me...but honestly the stock stuff is so worthless that I'm not sure it really matters.
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Old 03-21-2011, 11:33 AM   #9
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Quote:
Originally Posted by bxr140 View Post
First, there is no right answer.

Second, suspension fluid weight isn't really controlled by a standard (like motor oil) so unless you find a relative chart (googles PVD designs) you don't know exactly what you're getting. It's mostly relative, but there's a few out of family exceptions.

For a bone stock suspension, something in the "normal" 7.5-10w range will work best. Measure using ingenuity. I jus use a zip tie or a half inch wide scale, then pour in/out as required. A small discrepancy between forks will have zero effect on suspension action so don't worry about being crazy exact. Within a mm or two is fine. Make sure you pump the damper to get all the air out first.

For oil height, I'm currently using about a 120mm air gap. Makes the suspension less stiff deep in the stroke. Seems to work okay for me...but honestly the stock stuff is so worthless that I'm not sure it really matters.
Yep, what he said the numbers on the bottle for fork oil don't mean a thing.
My converted forks have 100mm air/oil and a "Maxima 7.5 wt" oil which is about the same as the Golden Spectro stock stuff that Marzocchi uses. Like this page says the numbers are not standard accross brands http://www.pvdwiki.com/index.php?title=Suspension_Fluid

The best recommendation is to pick one brand and stick with it as you change from one wt to antoher. One company's 10wt can be another's 5 wt.
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Old 03-22-2011, 01:54 AM   #10
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So the stock oil height is 60mm but increasing the air gap is ok, even recommended? I'm about to put some progressive springs in my forks but this will be my first time opening up a motorcycle fork. I've worked on just about everything else except suspension. Thanks for the great info as always.
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Old 03-22-2011, 07:01 AM   #11
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The Hyperpro front spring kit has some instructions on their spring which is greater than the stock recommendation. To some extent the air gap is a rider preference determination. Air compresses, oil does not. The purpose is to stiffen up the upper stroke of the compression to prevent bottoming the suspension. That is determined by how, where and the weight being carried.

The stock springs are pretty weak. If you are increasing the spring weight, I would start with a larger airgap and add oil as needed.
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Old 03-22-2011, 07:38 AM   #12
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Quote:
Originally Posted by itsatdm View Post
start with a larger airgap and add oil as needed.
Very good advice. It's much easier to add oil than it is to remove oil...

bxr140 screwed with this post 03-22-2011 at 07:48 AM
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Old 03-22-2011, 08:33 AM   #13
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Quote:
Originally Posted by itsatdm View Post
The Hyperpro front spring kit has some instructions on their spring which is greater than the stock recommendation. To some extent the air gap is a rider preference determination. Air compresses, oil does not. The purpose is to stiffen up the upper stroke of the compression to prevent bottoming the suspension. That is determined by how, where and the weight being carried.

The stock springs are pretty weak. If you are increasing the spring weight, I would start with a larger airgap and add oil as needed.
Quote:
Originally Posted by bxr140 View Post
Very good advice. It's much easier to add oil than it is to remove oil...
+2

Hyperpro specs a 120mm air gap for the regular progressive springs kit and a 60mm air gap for the heavy duty progressive springs kit. According to Klaus at Hyperpro USA you do not need the heavy duty springs for this bike unless you are running the Touratech oversize tank. He divulged that the standard springs kit is stiff enough for even some one up to 240 lbs or even more. In fact, he revealed that that is the only reason Hyperpro created the heavy duty kit is for the Touratech tank. I assume everyone who has purchased the Hyperpro progressive springs kit that does not have the Touratech tank are using the standard kit. Therefore, start with the recommended 120mm and add oil if need be. Get one of these, it makes the worry about correct height go away. You just keep sucking out oil until it won't suck anymore. Then you know you're at your set height. Invaluable.

You can't see it in this pic, but there is a millimeter ruler/scale on the metal "straw" part. You simply set the circular stopper to the desired mm, put it in the fork tube and suck til it doesn't pull oil anymore.

http://www.amazon.com/Motion-Pro-For.../dp/B000GZPCYI $18



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Old 03-22-2011, 10:46 AM   #14
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Great info as always. Any videos out there showing fork spring removal, etc? A bit off topic, but what are your guys' thoughts on upgrading the springs vs. all new cartridges? I'm soliciting as many opinions on this topic as I can get before I seriously consider spending that kind of scratch. For the type of riding I'll encounter on the CDT this summer will simply upgrading the springs suffice?
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Old 03-22-2011, 10:55 AM   #15
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I can't get the link here at work, but there's a series of videos floating around YouTube for the Bitubo cartridge installation... Pretty much the same thing as spring removal.
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