Rear Shock & Front Fork Info Requested

I need to change the rear shock on my bike if it is stock. The Question is since I bought the bike used, how do I identify that the shock is the original one that came with the bike which is suppose to be a 4.6.

Second question, I want to change the fork oil in my bike and was wondering if there is a specific fork oil weight other then stock along with the fill amount that may help my front forks work better then the factory setting. My bike is a 99 WR400 and I weigh 200 lbs. ready to ride. I have read in the forum that my front forks are a bit harsh threw the center of the stroke and wanted to see what I could do to approve on this. Race Tech shows the front fork springs are set up for a 200lb rider so I should be good there.

5 weight oil seems to work best on the WR's . I like 100 mm from the top of the tube. Stock fork valving is not very good so you may want to send them out to Race tech or MX-Tech for revalving as well. Go with a 5.2 kg or 5.4 kg rear spring as well. :thumbsup:

Don't forget to change the fork oil fairly frequently, it can get pretty gluggy if you leave it a while. It is very easy to change.

the lighter the weight, the plusher it will be. People use a heavier weight fluid to compensate for soft valving. People are happy doing so, nothing wrong with it, but the benefits of a revalve are huge.

Your bike is getting on a bit, the shock could probably do with an oil change and a re-gas. It has probably never been done before.

All depends on how long you want to keep the bike and how much you want to spend on it. Just servicing the forks and shock will see a big improvement, but getting it revalved and serviced professionally is obviously the best option.

Don't forget you can mix suspension fluid weights so if 5wt too soft or thin, drop the level a bit and add some 15wt.

I use ATF in my forks on all my bikes and have been doing so for years - Haven't had any shit to date and after doing the forks on my WR400F about a year ago , still no leaks and the suspension set up is still perfect - We ride every 2nd weekend - ATF is also a damn site cheaper than your fancy brand fork oils on the market . I would agree with Indy with the measurement of about 100mm from the top for your weight - If you strip your forks completely and they are dry when you reassemble them , they will take 600ml of oil to get to the 100ml level - Dont forget to pump the the damper rod up and down when filling the fork to dstribute the oil evenly .

While we are talking about springs and oil for the WR, can someone please clear this up for me. What is the effect of having stiffer spring as opposed to having more standard oil in the forks as opposed to a heavier weight oil?

Is the outcome the same for each option? Maybe a link to a website may help me to understand the differences.

thanks in advance,


110kgs (242 lbs) with all riding gear and loaded camelbak.

This is what I understand -

heavier weight oil will slow down dampening, which is fluid moving passed the shims. Like honey compared to water.

More or less oil effects the stroke length. More oil will cause the suspension to hydrolock earlier. Not to sure about this one.

Springs just hold the bike up. With stiffer springs, you can have very plush suspension (use light weight oil).

In brief:

Front and rear pring rates are critical for maintaining proper ride height and stability during off road riding. It is important to have sag set to approx 1/3 of the overall travel so that the suspension can work as designed. The springs have no dampening effect. That is why we run oil in the front and rear shocks to make sure we either dont pogo or compact. Valves control the oil flow on a high speed and low speed impact or compression as well as on the return or extension. :thumbsup:

Some day it will all be electronic controlled dampening with a micro chip and multiple overlaping dampening circuits. :bonk: For now we got a few things to adjust. Anyone over 180 lbs with gear should not be riding stock suspension. :thumbsup:

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