Fork Oil?

6 replies to this topic
  • WRC51

Posted May 31, 2009 - 08:32 AM


Iam going to be replacing my fork seals this week, Yamaha calls for their"S1" fork oil. Does anyone know what weight that oil is? Iam going to go with a slightly heavier weight. Thanks

  • dazzabb

Posted June 01, 2009 - 04:45 AM


Most folks opt for 5 wt fork oil, dunno what the S1 designation is equivalent too.

  • WRC51

Posted June 01, 2009 - 05:00 AM


Thanks dazzabb, I was going to use 10 wt. but after some research will try 7 wt. Hopefully a good starting point. I was told to try the slightly heavier oil wt. as opposied to heavier front springs. Worth a try I think.

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  • trailhead2004

Posted June 02, 2009 - 10:59 AM


Be careful changing oils in your forks. The S1 is a suspension fluid, probably about a 2.5 wt or so. It's consistency is much more like brake fluid than oil.

It might just be a marketing scheme, but I would at least ask the dealer about it or consult a suspension expert. Come to think of it, there's one here on TT you can ask.

My $.02.


  • matt4x4

Posted June 02, 2009 - 11:16 AM


Oil viscosity won't make much of a difference, valving and spring rate will make the difference. Greyracer described once why oil weight won't make much difference - you might want to search for his post on it.

you can tighten it up in the last few inches of travel, slowing it down shortly before blowing through the stroke by setting your oil height a little higher (check your manual for limits).

  • SXP

Posted June 02, 2009 - 01:02 PM


I run Mobil 1 ATF (the full synthetic stuff) in the forks of my WR400s with great results. This oil gives you a feeling of plushness/slickness when compared to your typical suspension fluid that's hard to describe, and it doesn't fade after a period of hard riding. It's is slightly heavier than a 5W suspension fluid so some clicker tweaking is in order to get it setup correctly.

I just did my first fork/shock oil change (after the ESP revalve) on my 07 WR450, and opted to try DaveJ's ( 215/VM2-K5 suspension fluid. The oil cost about $75 shipped for both the forks and shock. I have yet to ride the bike since the change, but have heard great things about this fluid, so I'm anxious to try it out.

  • WRC51

Posted June 02, 2009 - 04:06 PM


Hey guys thanks for all of the info concerning the forks. I did go with 7wt. in the forks along with new seals and the metal sliders(?) on the inner fork tube. I will check it out this weekend and report the results.


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