fork oil weight?

3 replies to this topic
  • Venom01

Posted August 29, 2009 - 07:00 AM


2005 yz 450, the manual says to use yamahas sp1 fork oil, what weight is that so i can get some other brand? its like 40 bucks a can plus i need just over one when replacing the oil. seems like they know how to stick it to you.

  • grayracer513

Posted August 29, 2009 - 07:49 AM


No one has ever been able to definitively answer the question of what the viscosity of Yamaha S1 is, but any good fork oil in 2.5-5wt will do. Amsoil Shock Therapy is one of the better conventional oils, as is Motorex.

Viscosity doesn't matter as much as many believe, since fork valving is essentially a pressure regulation system, rather than a bunch of controlled orifices. The viscosity shift between 70 and 160 degrees oil temp is about 3 times greater than the difference between 3wt and 7wt, anyway. After you make a couple of clicker adjustments for the different oil, they will more or less behave the same across a wide viscosity range.

Some, including myself, like to run a heavier oil in the outer chamber to improve the performance of the bottoming brakes while running a little lower oil level for better overall feel.

The best oil you can use, IMO, is a rather unconventional product from SMART Performance: 215.VM2.K5. Use the lighter SP3 in the inner, and SP5 in the outer.

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  • Venom01

Posted September 06, 2009 - 03:47 PM


thanks for the reply, i have asked many people and shops this question and this was by far the best reply i had recieved.

  • davbrucas

Posted December 11, 2009 - 09:43 AM


He isnt called GrayRacer for no reason! When you have been alive for 60yrs you tend to pick up some useful info along the way! :banghead:

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