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Captain Bob

Fork Oil Question

11 posts in this topic

My bike is a 99 Wr400. Front end seems stiff and is not using all of its travel.

What weight oil would anyone recommend for the front forks of a stock WR 400? I am unsure whether I should be using 5 wt or 2.5 wt. I am a big dude (260 w/o gear). I use the bike for general trail riding.

Do not know what the current weight oil is. Front springs appear to be stock with no preload washers inserted. It seems the current fork oil is about 90mm's from top of tube. With this set up, Forks currently do not use their full travel and seem a little stiff. I have opened up compression to within 1 click from the minimum setting. That helped a lot but, after a ride where I should have used at least 80% of fork travel, my travel indicator (zip ty on fork leg) is 3 inches from bottom of inner tube. I would expect it to have been within 1 inch.

I am going to replace the oil and would like to get some ideas on what weight to use. Also, what would the recommendation be for the level of the oil in the tube? I understand the range is 80mm's to 145mm's.

Appreciate any help!

Bob

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I had the same problem you did. I had all stock springs in fork and shock. I called RaceTech and put in new valves and springs and I can honestly say that's the best decision I've made on my bike. Mine is a WR 426 and I love it more now than I ever did. I have my fork oil (2.5 weight) set at 90mm. I'm 210 w/o gear and with your weight being closer to normal for adult riders instead of using the springs the factory sets in the bigger bikes for 10th graders I really think you'll be astounded at the difference and the confidence you get with new springs/valves. My $.02 worth.

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I have the manual but it only tells me to use KYB 01 oil. I think that oil is less then 5 wt. I could be wrong however. I may try the combination HamBone 23 is using which is 2.5 wt at 80mm's. I may also start looking for some heavier springs although, The current set up with the stock springs is not even close to being to soft. Perhaps with the 2.5 wt oil things will significantly soften up. I do apprciate both responses. I am sure this has been discussed a gazilliobn times before so I apologize for bringing it yup again. I did search the archives but never really got an answer to my question. Thanks again for responding!

Bob

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Going from 90mm to 80mm is going to make it even more resistent to bottoming. I would try going back to the stock spec and work from there. I cant imagine the stock setup being too stiff for someone who is 260.

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Going from 90mm to 80mm is going to make it even more resistent to bottoming. I would try going back to the stock spec and work from there. I cant imagine the stock setup being too stiff for someone who is 260.

I think you may have misunderstood, If I go to the 80mm oil height it will be with 2.5wt oil vs what I believe may be 5 wt which is currently in the bike. The thinner oil will surely make the bike feel more "supple". Would you agree?

Bob

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Where would you suggest the oil height to be using ATF?

Bob

well ive heard that atf is like 2.5 to 5 wt. so you could stick to the 80-90 mm height. :banghead:

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well ive heard that atf is like 2.5 to 5 wt. so you could stick to the 80-90 mm height. :banghead:

M-1 syn ATF is closer to 7.5 wt,but i use it with excellent results :banghead:

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I have heard a lot about ATF. Actually, in the old days (I am an old dude!), ATF was the oil of choice for most MX'rs. I think use of ATF now with the stock springs and valving will only worsen my problem because it is a heavier oil. I will try the 2.5 wt first then see what happens.

Thanks again for all responses!

Bob

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