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Buell Forum » 1125R Superbike Board » Archives 001 » Archive through October 30, 2010 » What is the proper fork oil level? « Previous Next »

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Xodot
Posted on Monday, October 25, 2010 - 10:17 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The table on Page 1-8 of the shop manual says 117mm from top of tube.

In the assembly instructions the level is quoted at 94 mm from top of tube.


ALSO: the rebound setting on one of my forks has a range from all in to all out of about 2 1/2 turns, the other fork has a range of 3 1/2 turns. Why the difference? Is this a problem?

(Message edited by xodot on October 25, 2010)
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Rodrob
Posted on Monday, October 25, 2010 - 12:29 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Anywhere from about 90 to about 125, but I don't know anyone who uses less that 100. Fork oil level is a good way to fine tune the spring rate of the forks. Because air compresses progressively, dropping the fork oils can give a softer high speed initial feel while still maintaining bottom out protection. It can also help to get you to the sag setting you are looking for if you are at the stiff end of your spring rate.

ALSO: one of my forks has a range from all in to all out of about 2 1/2 turns, the other fork has a range of 3 1/2 turns. Why the difference? Is this a problem?

Are you talking about preload?
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Xodot
Posted on Monday, October 25, 2010 - 01:06 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Interesting use of oil level. Thanks Rodrob.
I have edited my post to read correctly - sorry for the confusion. I was referring to the rebound settings screws having different ranges of motion.
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Zac4mac
Posted on Monday, October 25, 2010 - 09:30 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

hmmm, now I'm interested.
Front-end of my Uly is like that.
One leg adjusts as expected, the other turns 1/4 as much as it should.

Fork service is scheduled for 20k and it's at 18.6k now.
Feels OK so I'm letting it ride until I tear the tubes apart.

Unless you uncover anything scary...

Z
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Jdugger
Posted on Monday, October 25, 2010 - 09:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

And keep in mind it's not necessarily bad to have your fork settings mismatched. As long as the triples are rigid and the system is working, it's OK.

On my AK-GAS set up, one fork leg is compression, and one fork leg is rebound, for example.
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Xodot
Posted on Tuesday, October 26, 2010 - 11:29 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Jdugger - what is the point of setting the forks up differently? What advantage is realized? Don't the forks fight against each other (each trying to do it's own thing) under load change? This is another of those counter-intuitive things which fills motorcycle engineering!
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Jdugger
Posted on Tuesday, October 26, 2010 - 11:32 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Well, in the case of the AK-GAS cartridges, one fork leg is responsible for compression damping, and the other for rebound. They don't "fight" since each leg only has damping functionality in a single direction.

We need a mech. engineer to confirm, but I think when you have two damping devices rigidly coupled, the damping effects don't fight, it's simply a sum function of the two devices.
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Rodrob
Posted on Tuesday, October 26, 2010 - 12:23 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

When bolted together by the axle, the forks behave as one unit. At a recent test track outing on a prototype bike, Higbee ran with only one fork spring to get to a super light spring rate.
However for us mortals, go to traxxion.com and look at the fork installation section. There are instructions for calibrating comp and rebound prior to assembly so that the forks match.
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Xodot
Posted on Tuesday, October 26, 2010 - 07:29 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

When bolted together by the axle, the forks behave as one unit

... so does this mean the net result of two forks at different settings is the average of each setting?

By this I mean to ask: If the left fork has 1 turn of rebound set and the right has 2 turns of rebound set, do the forks together respond as if they have 1 1/2 turns of rebound?
(this is what the Higbee example of only one spring is sounding like to me.)
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