How much fork oil per leg?


7 replies to this topic
  • jams229

Posted May 19, 2008 - 02:12 PM

#1

I understand the fill to specs, but I am curious if anyone knows how much oil goes into each fork so I know how much to buy. 2007 WR450.
Thanks a lot.

  • grayracer513

Posted May 19, 2008 - 03:14 PM

#2

You will need something on the order of 38 ounces (roughly, depending on where you set your oil level, and how much you spill), so plan on buying two quarts.

  • jandmsuburban7

Posted May 20, 2008 - 11:17 AM

#3

Hey Gray, 3 quarts is easier so you can fill to the top and pump it better.

Hey Jams, got a manual? I go about 30 or 35 cc's over what is called for with good quality racing fluid. That insures me not to bottom out if I hit the big one. I am 200 lbs. and ride hard but dont want to spend the money for new springs and valves. I dont bottom out anymore and I dont sacrifice my plush ride on the single tracks either. Jason

  • grayracer513

Posted May 20, 2008 - 12:36 PM

#4

Hey Gray, 3 quarts is easier so you can fill to the top and pump it better.

Two has been plenty for every single chamber Kayaba fork I've ever done.

Also note that the oil fill capacity is not called out as a volume, but as a level. In the spec pages, the manual does list 648cc (just shy of 11 ounces per side), but if you review the fill procedure in section 5, you'll see that the fluid is adjusted to a set level, ranging between 150 to 90 mm below the top with the tube and rod compressed, and no spring present. So when you say you use 30cc more than called for, it doesn't mean as much as if you had said that you run the level at 115, instead of the standard 132.

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  • jams229

Posted May 20, 2008 - 01:04 PM

#5

Thanks all for your input.
I am still amazed at the lack of knowledge out there among YAMAHA dealerships. I called 4 of them today and received 4 DIFFERENT answers! I couldn't believe it! My question was regarding the
weight of the S1 suspension fluid for the forks. I literally got a different answer from all 4 shops: 5, 7.5, 10, and 12! What is Yamaha's reason for keeping this fact so secretive, other than selling more of their S1 fluid?!
I would think they would want the owner to know what they had in there so the owner could make an educated guess from there as to what weight they would want to use. Am I crazy. stupid, or both?? :thumbsup:

  • grayracer513

Posted May 20, 2008 - 01:36 PM

#6

Thanks all for your input.
I am still amazed at the lack of knowledge out there among YAMAHA dealerships. I called 4 of them today and received 4 DIFFERENT answers! I couldn't believe it! My question was regarding the
weight of the S1 suspension fluid for the forks. I literally got a different answer from all 4 shops: 5, 7.5, 10, and 12! What is Yamaha's reason for keeping this fact so secretive, other than selling more of their S1 fluid?!
I would think they would want the owner to know what they had in there so the owner could make an educated guess from there as to what weight they would want to use. Am I crazy. stupid, or both?? :thumbsup:

You might be, but that's not important right now.

The viscosity of Yamaha (KYB) fluids is not on the label because it doesn't make that much difference one way or other. Modern suspension units are built to operate through the use of pressure differentials within the unit, and not on flow rates through orifices as in the past. This allows them to perform consistently over a wide range of temperatures. The viscosity of most fork oils, even as high as their viscosity index is, changes much more between 60 - 140 degrees F than the difference between a 5 and a 10 weight oil.

The only place that a more viscous fluid makes much difference at all is in the hydraulic bottoming cones used in many forks.

In answer to the question of which weight to use in your fork, 5wt would be most common, but 3-8wt is just as acceptable.

  • jandmsuburban7

Posted May 20, 2008 - 02:59 PM

#7

Hey Gray, so you put a pre-measured amount in? Or do you measure from the top down. And does it matter as long as it is the same amount in each tube? I just try to follow the directions and do things without cutting corners until I've experienced enough to know where I can cut corners! (not just on bikes) It would sure be easier to just pour it in without trying to add a little and suck out a little.
Hey Jams, also, the labels on many of the containers dont even express a certain weight and the ones that do say a certain weight can be different than another brand with the same weight. This having already been described by Gray.

I would think they would want the owner to know what they had in there so the owner could make an educated guess from there as to what weight they would want to use. Am I crazy. stupid, or both??

Makes you wonder how, if you have your bike serviced at these places, your bike still runs after their servicing!!?!!

  • grayracer513

Posted May 20, 2008 - 03:42 PM

#8

Add 9 ounces and measure it, adding as necessary. An alternative is to connect a tube to a basting syringe, or any similar device, measure the desired length to the correct level and insert the tube to that depth. With this, you can draw off any excess easily.

Fluid level in the fork makes a good deal of difference, actually, since the captive volume of air above the oil becomes a de facto spring. Adding additional oil essentially increases the compression ratio within the fork. Lower levels make the fork plusher, but encourage foaming and perhaps bottoming. Higher levels discourage foaming and resist bottoming more, but at the expense of a harsher ride.




 
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