Tip for measuring fork oil height

Maintenance, repair, troubleshooting, etc.
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radare
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Fri Jan 06, 2012 11:12 pm

I came up with this last year while doing the fork overhaul on my SV650. To measure the height of the fork oil in the fork tube, compress the fork without the spring, add the recommended amount of oil and then use a long zip-tie as a dip-stick. The little grooves on the zip tie will give an accurate location of the oils height. I simply push the zip tie into the fork and rest it on the square head. I then count the measure the oil level on the dipstick, with calipers, and then adjust by adding or removing fluid.

The fork oil should be 111 mm (4.37 inches) from the top of the compressed fork tube on '92-'95 Seca II's.
The fork oil should be 116 mm (4.57 inches) from the top of the compressed fork tube no '96+ Seca II's.

The capacity is approximately 12.8 ounces (US) of fork oil per fork leg, for all Seca II's.

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1Oldman
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Sat Jan 07, 2012 1:14 am

How critical do you think the fork oil height is radare? Let's say both forks have an equal amount of fork oil but the height is off by a half inch or so. The only thing that I can see is maybe some change in the compressibility of the air above the oil. :geek:
Better to be over the hill than under it.

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radare
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Sat Jan 07, 2012 7:36 am

That's a good question! I think the different volumes might have a small affect as there would be more hydraulic pressure during movement of the fork piston in the one that had more fluid, but since the pair of forks is a linked system, I don't think the rider would notice the difference, honestly. I've always made an effort to get them exactly the same, though.

EDIT: Here's an interesting article on setting up forks, that mentions the effects of fork oil weight and level. TRIALS SUSPENSION TIPS, by Jon Stoodley

The author indicates that fork oil level affects compression damping while the fork oil weight (viscosity) affects rebound damping. Specifically, higher oil levels within the shock will provide more compression damping (i.e if you're running 4 inches oil height, the forks will provide a higher damping force than if you're running, say, 6 inches).

Here's an exerpt from the article that helps clarify the affects of oil height:
That air pocket inside the top of the fork tube acts as a secondary spring as it is compressed when the bottom slider moves up. Raising the fork oil level makes for a smaller air pocket that takes more energy to compress ( per inch of travel ) than a larger one and will exert more pressure to assist the spring extending.

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Pasinby
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Sat Jan 07, 2012 8:24 am

I use a ruler as a dip stick , 4.25 inch , not spec but , for me it works . :moped:

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1Oldman
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Sat Jan 07, 2012 9:55 am

radare wrote:
EDIT: Here's an interesting article on setting up forks, that mentions the effects of fork oil weight and level. TRIALS SUSPENSION TIPS, by Jon Stoodley

The author indicates that fork oil level affects compression damping while the fork oil weight (viscosity) affects rebound damping. Specifically, higher oil levels within the shock will provide more compression damping (i.e if you're running 4 inches oil height, the forks will provide a higher damping force than if you're running, say, 6 inches).

Here's an exerpt from the article that helps clarify the affects of oil height:
That air pocket inside the top of the fork tube acts as a secondary spring as it is compressed when the bottom slider moves up. Raising the fork oil level makes for a smaller air pocket that takes more energy to compress ( per inch of travel ) than a larger one and will exert more pressure to assist the spring extending.
Thanks for the good info radare. Although I try to maintain my forks by factory standards, I can't help to think of all those years that I just made sure there was fork oil in my forks and everything seemed to work fine. If I wanted to change my dampening, I just changed oil viscosity. Never too old to learn I guess. :1Oldman:

Maybe we should find a place on The Wall for this article.
Better to be over the hill than under it.

Oizarod115
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Tue Jan 10, 2012 8:55 pm

the easiest way I've done is to buy a clear turkey baster from Wal-mart or other box store (2$ or less)

measure out your fork oil height on the baster and put a tape line on it.

lower the baster into the fork to the tape line and suck out the excess fluid (or add fluid if its under that amount)

For a good read go to your local bookstore, purchase a coffee, and take up RaceTechs "motorcycle suspension bible"

it is amazing. just read it.
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1992 XJ600 Naked, V&H 4-1, FZR600 forks + clip-ons, R6 Blue-Spot Calpers, Corbin Seat (Really gotta control my spending better)
1989 Jeep Comanche 6" Lift 33" BFG MTs
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1Oldman
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Tue Jan 10, 2012 9:30 pm

Oizarod115 wrote: For a good read go to your local bookstore, purchase a coffee, and take up RaceTechs "motorcycle suspension bible" it is amazing. just read it.
Somehow I can't see Barnes & Noble having that in their inventory. :grins:
Better to be over the hill than under it.

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docter911
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Sat Jan 12, 2013 10:48 pm

so why not overfill the forks a bit and use an oil suction gun?

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Tilos
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Sun Jan 13, 2013 11:57 am

radare wrote:That's a good question! I think the different volumes might have a small affect as there would be more hydraulic pressure during movement of the fork piston in the one that had more fluid, but since the pair of forks is a linked system, I don't think the rider would notice the difference, honestly. I've always made an effort to get them exactly the same, though.

EDIT: Here's an interesting article on setting up forks, that mentions the effects of fork oil weight and level. TRIALS SUSPENSION TIPS, by Jon Stoodley

The author indicates that fork oil level affects compression damping while the fork oil weight (viscosity) affects rebound damping. Specifically, higher oil levels within the shock will provide more compression damping (i.e if you're running 4 inches oil height, the forks will provide a higher damping force than if you're running, say, 6 inches).

Here's an exerpt from the article that helps clarify the affects of oil height:
That air pocket inside the top of the fork tube acts as a secondary spring as it is compressed when the bottom slider moves up. Raising the fork oil level makes for a smaller air pocket that takes more energy to compress ( per inch of travel ) than a larger one and will exert more pressure to assist the spring extending.
And my reason for adding schrader valves to the fork caps of every bike I own.
My most recent purchase came with factory valves and a sticker that says "6 psi max".
As we discussed before, I fine tune with air pressure using a Mtn bike suspension pump capable of charging a fork without any loss of air at pump removal.

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arnehulstein
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Sun Jan 13, 2013 12:54 pm

I just found the exact number of cc's in the manual and put that in. No need to measure the height then. Or not as far as I would know.

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