fork oil viscosity?



9 replies to this topic
  • Henry

Posted July 21, 2000 - 09:03 PM

#1

Guys, just changed my fork oil.
Used a castrol fork oil,but never state what is the viscosity.But it feel as stiff as before!!!Did I used the wrong fork oil?
For my weight, the stock fork spring is too stiff for me. Can lighter viscosity oil reduce the stiffness??
Think I will change my fork oil very soon again.
I need advice on this, guys.
Thanks!

  • Kevin_in_New_Hampshire

Posted July 21, 2000 - 09:30 PM

#2

Henry,
Have you backed out your compression clickers fully (they are the ones on the bottom of your fork tubes)? Make sure they are the same number of turns out from the full in position.

------------------
99 WR, all YZ mods, de-octopused, OEM YZ tank and IMS seat, jetting by Clark, got forked by Pro Action, WAITING IMPATIENTLY FOR MOAB!!
AMA, NETRA

  • John_in_Long_Beach

Posted July 21, 2000 - 09:55 PM

#3

Henry,

You are just beginning to embark on the frustration of Yamaha 01 fork oil.

Read my recent posts on fork oil.

Here is a summary of what I have learned.

1 )Yamaha 01 for oil is "not a fork oil"

Yamaha or anybody in the surrounding industries is either
A) correct to not give the oil a weight
or
:) Too stupid to assign a comparable weight to the oil

2) You should not use any other oil execpt Yamaha 01 or Enzo zero weight which is Yam 01

because

A) All hell with break loose and your forks will not work and you will die.

or

:D Other people have used other oils without any problems and with many success.

3) The only way to properly adjust the forks is to use Yamaha 01 fork oil and the use the clickers. But if you are at the limit of the adjustments. You should.

A) Get the forks revalved with diffent valves, because this is the only proper way to adjust the valves and the integrity of the system will be compromised because you need to use Yamaha 01 oil.

or

:D You can use other oils to increase or decrease the dampening. But nobody has a clue as to what the baseline vicosity of Yamaha 01 is and/or the "tuning experts" have no idea what they are doing, and/or you have taken money out of the wallets or the tuning experts.

So there is either no knowledge by the experts as to what other oil options there might be or it is not in their financial interest to disclose this as an option, or maybe different oil really isn't correct.

So after a couple days of investigation I have no clue as to whether the retention of Yamaha 01 oil is a necessity

or

Whether it is completely industry bullshit and hype.

Maybe you can learn something that I haven't

John

  • Henry

Posted July 23, 2000 - 04:00 PM

#4

Good days guys, went home after riding yesterday.
When I'm riding slow on pathed road, it seem that my front wheel is riding over small pebbles those kinda feeling.
But when I ride at faster speed, the vibration feeling is gone.
What causes the problem? My front fork?
I'm getting worried!! Help guys!!!

  • Kevin_in_New_Hampshire

Posted July 23, 2000 - 04:56 PM

#5

I thought I read in National Enquirer a Whistleblower publicised the actual weight of Yamaha 01. He was later found buried under 20 feet of solid granite. Rumor had it his lungs were full of Yamaha 01...

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  • Kevin_in_New_Hampshire

Posted July 23, 2000 - 05:02 PM

#6

Henry,
Although I do not fully understand your problem, you may want to check your front wheel bearings and your steering bearings.

If your compression clickers are set too stiff, your front forks will resist moving, especially if you have stiffer than normal fork oil (see preceding message from me). The damping on the 99's is poorly setup and causes the forks to resist initial movement. I thought it might be seal stiction, but Pro Action told me the damping is setup wrong...for what it's worth.

Kevin

  • DaveJ

Posted July 23, 2000 - 08:56 PM

#7

Henry,

Perhaps this will help.

A fork spring is what controls how stiff or lose your bike will ride. Valving controls the spring.

Each spring rate has a minimum and maximum amount of valving required to keep the spring under control. I call this a "valving window" since too much or too little valving can cause the spring to have too much or too little control over the bike.

You'll find that with little or no compression valving, the bike will actually ride rough and feel out of control, (ie "springy"). If you remove the rebound damping, the bike (and wheel) will want to float above the ground, causing front-end float and therefore comprising traction. (I'll explain how if anyone wants to know).

You'll find, with experimentation, what your valve-window is for a particular spring.

Here's the best way to set the front end of the bike.

First, ride the bike and determine if the back end of the bike bucks when hitting bumps. If it jumps up in the air or thrashes from side to side, you need more rebound damping on the rear. Turn the screw in (clockwise) on the bottom of the shock one click at a time until the rear end rides smooth. I start with this because lack of rear shock rebound damping often causes the bike steering to be erratic, (it thrashes from side to side) causing us to think that the forks must be causing the problem. Once this is under control, the rear of the bike will stick, and the front end will want to point in the intended direction. You’ll find that many riders lack this, indicative of their bikes wanting to re-launch themselves after a hard landing or a back wheel clip of a bump.

Next, find a smooth flat road without gravel or rocks. Accelerate the bike to about 15 MPH then brake hard using only the front brake. Brake as hard as possible without wheel lock. During this braking, the front forks will compress. Hold the brake, and at the point the bike completely stops, the fork will want to rebound, then compress, then perhaps rebound and compress again. This oscillation needs to be controlled by turning in the rebound damping screws (on the top of the forks) clockwise. Turn in each screw one click, repeating the test, until the fork rises (rebounds) with little or no following sag. If you have set too much rebound, the suspension will compress and remain compressed over a section of bumps (this is often called "packing").

The final step is to introduce compression rebound one or two clicks, (bottom screws) riding the same bumpy trail until you begin to feel the bike ride smoother and with greater control. Ignore any slow speed ride qualities. The perfect ride will feel plush at the same time it feels smooth and firm.

With this setting, if you find that the bike rides too hard, you'll most likely have to switch to a softer spring. If you decrease spring rate too much, you may have to re-valve the forks for a valve setting that is suited for the lessor spring, (not the easiest of jobs). Too much valving for a particular spring will cause the bike to feel “spoongy” and react slow to steering inputs.

Most suspension shops and local mechanics have their own ways of calculating what spring rate should be used...and the bandwagon follows. However, nothing works best than making up your own mind as to whether the bike rides hard or not. You may find that a .43 spring, although considered way too soft for today's standards, may be the best spring for your needs.

Hope this helps and let me know if you need any further details.

Dave

  • Henry

Posted July 24, 2000 - 02:32 AM

#8

Guys, just check my front wheel
Lock my handle bar to one side, I feel
very slight "tick tag" movement when I grab the wheel and move it left and right.Felt it in all direction, is this the bearing causing the "front wheel riding over uneven road feeling"?
Do I need to change the bearing, and how do I do it??
Thank guys.

  • Hick

Posted July 24, 2000 - 10:57 AM

#9

At the very least it sounds like you should check your steering stem bearings. They may be fried, need grease or your steering nut might be on too tight.

Take off top triple clamp to get at steering nut, loosen this nut with a pipe wrench. It should only be tight enough to remove slack. Too tight will result in resistance or drag (which sounds like what you have).

To regrease/replace just remove steering nut all the way and drop triple clamps out of frame.

  • Henry

Posted July 24, 2000 - 04:16 PM

#10

The bearing which got the "gap" feeling is in the hub.
It does not have a C-clip. So do I just knock it out from the speedo mounting side?
Thank guys for your helps. :)




 
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