fork oil for 2007 yz450?

5 replies to this topic
  • Hurricane

Posted December 26, 2012 - 10:37 AM


I went by the dealer to pick up fork oil because my seals are leaking and the dealer was telling me that my bike is supposed to use Yamaha S1 fork oil and nothing else will work, is this true? This stuff is $30 a bottle and as usual one bottle is not enough. Can you use a Bel Ray or some other brand and if so what weight is required?

Edited by Hurricane, December 26, 2012 - 10:38 AM.

  • grayracer513

Posted December 26, 2012 - 10:53 AM


You can use any other fork oil you might like. Use an oil between 3 and 5 wt. If you change oils, you should plan to drain/refill/bleed the inner cartridges as well, as some mixing of inner/outer oil does occur.

  • Hurricane

Posted December 27, 2012 - 10:28 AM


You can use any other fork oil you might like. Use an oil between 3 and 5 wt. If you change oils, you should plan to drain/refill/bleed the inner cartridges as well, as some mixing of inner/outer oil does occur.

Hi Gray thanks for the information. The dealer told me that if I use anything other than the S1 oil that it will affect the valving and the suspension will not work well, is this true? I would think that as long as the oil wieght matches the wieght of the S1 I will be fine.

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  • grayracer513

Posted December 27, 2012 - 02:01 PM


Neither of you is exactly correct, but you're a whole lot closer than he is. There isn't that much about the S1 oil that's all that trick, and frankly, I don't think that it holds up very well. Amsoil Shock Therapy is one of the better conventional fork oils available, but most of the major brand fork oils are really pretty good. Be sure you change both the inner and outer oil volumes whenever you switch from one oil to another. They're separated, but some mixing does occur.

Fork and shock valving is done for the most part by systems that amount to pressure regulators. If the oil is thicker (within reasonable limits), the valves will simply open farther to arrive at the designed pressure delta across the valve at a given stroke speed. If it's thinner, they just don't open as far. Notice that the difference in viscosity between a 3wt and a 7wt oil at any certain temperature is less than the difference between the viscosity of most oils at 70 ℉ and then at 160 ℉, and I doubt you think your suspension is very noticeably different acting at the third hour of riding than during the second 10 minutes. It's designed to adapt to that sort of thing.

A fairly major change in fork oil viscosity will affect the clicker adjustments noticeably, however, but that 's because those are fixed orifices, and as such are sensitive to oil weight. But in most cases, that would be it.

  • Hurricane

Posted December 28, 2012 - 07:31 AM


Thanks Gray I'll think I'll save myself some money and go with something other than the S1, I had planned on changing out the fluids in both inner and outers too.

  • Family Man

Posted December 29, 2012 - 10:18 AM


Buy two bottles of maxima 5wt or 3wt and you should be good for the inner and outer chamber. The amount of oil you put in the outer tubes is used for tunning and you can experiment with differant oil amounts. The book reccomends 350, you could try more or less depending on what you want. I put in less I thinkg 325-330cc's last time and its works good.

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