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ricky_arthur

Fork Oil weight???

5 posts in this topic

I recently replaced the seals on the forks on my yz426f. I'm a pretty good mechanic but new to motocylcles. At the Yamaha dealer where I bought the seals, I asked them what weight oil I needed and they gave me 10wt oil... so i replaced seals on both forks no problem, I put just UNDER the reccomended oil capacity to make them a little softer( i had hoped), and actually havn't noticed any real problem with them except that when I was riding with a friend today I noticed his forks where MUCH softer than mine. If he bounces on his pegs the front forks dip 2-3 inches. On mine they don't budge. They seem fine when i'm jumping etc(but like I said, I'm new and might not detect something wrong)Is this because he is on a WR450f and I'm on a YZ??? Or did I put the wrong weight oil in my forks. What weight should it be?? and what are the signs of fork oil being too thick??

Thanks

Ricky

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I'm not a Yamaha rider but I know the YZ forks are a lot stiffer than the WR forks. Yours is built for triple-jumps and the WR is built for trails, so yeah the springs will be different. Fork oil weight makes a difference but not that big a difference.

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The springs are what set your ride height and the first bit of travel, the oil with your air gap is what takes over as your springs from about 1/4 of the stroke on down. So if your forks feel harsh mid stroke when riding you may want to try to lower the oil level more, but if your only complaining about them being too stiff right at the beginning, you may have too stiff of a spring for your weight.

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The specified weight for the 426 fork is 5wt, but fork oil weight has little to do with the plushness of the fork. Modern suspension is designed to work the same across a wide viscosity range so it won't change character with temperature.

Oil level is a factor with this fork, however. There is no fixed quantity of oil to be used in the fork, but rather, the oil level is set between a high and low point (85-130mm down from the top of the tube, with the tubes and damper fully compressed, and the springs removed. Lower oil levels produce a plusher ride, but can allow excess bottoming.

The point about the YZ fork being harsher than the WR is correct.

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The specified weight for the 426 fork is 5wt, but fork oil weight has little to do with the plushness of the fork. Modern suspension is designed to work the same across a wide viscosity range so it won't change character with temperature.

Oil level is a factor with this fork, however. There is no fixed quantity of oil to be used in the fork, but rather, the oil level is set between a high and low point (85-130mm down from the top of the tube, with the tubes and damper fully compressed, and the springs removed. Lower oil levels produce a plusher ride, but can allow excess bottoming.

The point about the YZ fork being harsher than the WR is correct.

OK thank you I suspected as much.

I'm 6'3" and 190 w/out riding gear so I would be surprised if I was too light for the springs... I still need to set my static and race sag , but havn't because again I'm too new to know if it's incorrect now. I know, I know i need to check it. :thumbsup:

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