"98 YZ 400 Fork Problem

PWDAD

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#1
I am an aggressive 5-10" 215 lb "98 YZ 400 rider. I would say that I am an intermidate riding level. The problem that I am having is I keep blowing fork seals every couple rides I do a seal.

I believe that the fork springs are still the stock spring. Could this be part of the problem? What would be the best set up for me to try and whould should I change with the forks.

Thanks,
PWDAD
 
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#2
You really should got to stiffer springs frt. & rear. Have you made sure there are no small nicks in the tubes? Have you changed the bushings also? What oil height are you running?


doc
 

PWDAD

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#3
Doc:

I do not believe that there are any nicks in metal of the lower fork tube. I am not sure the actual oil level, only because my neighbor/Mech. helps my son and I with all of our bike work. I jsut had the fork serviced approx. 2 months ago and I am not sure if the bushing were changed at that time, I have not changed them myself. I will ask him what level, I would assume stock and check the bushings.

If I replacd the front springs would I have to replace the rear. I do not seem to be bottoming hard in the rear, but I hit real hard in the front at times.

Do recommend that I send the shocks off to be serviced by a professional facility, if so who do you guys recommed and what type of cost am I looking at?

Thanks
PWDAD
 
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#4
Dad
First off yes, if you change the frt. you will need to change the back. It's all a matter of balance. With stiffer fork springs more weight will be transfered to the back, so you want to keep both ends working together.

Next, every time that you slide the forks apart to replace seals you will usually tear the teflon on the bushings and so they should be replaced to keep the forks moving smoothly. Sometimes if you heat the seal & bushing area a little they will come apart a little easier but you want to really look at them close.

doc
 

PWDAD

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#5
Doc:

Thank you for your reply. Is this something I should actually have sent to a specialist to have completed. If so, who do you recommend.

What are the levels from stock for stiffer springs and how stiff would I want to go?

PWDAD
 
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#6
Dad
The stock rates are 5.4 on the rear and .45 up frt. My suggestion would be 6.0 rear and .50 frt. if they were revalved. Probably 5.8 & .48 if not. Oil height 105-115 depending on springs & valving. This would be for your size & weight aggressive MX. A little lighter if woods or playing.

As far as sending out to a reputable suspension builder, yes it would (should) make a big diff. They don't allow spamming here so just find someone in your area that has had his suspension done & is happy with it. If you ask around you will find someone that does a good job. A lot of times a smaller well known name that gives personal service will be better than a bigger name. Good Luck


doc
 

BSWIFT

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#7
Seems to me that on the left side of the screen there is a link to a real top notch suspension guy (white oval a little hard to read). As for the rate springs and oil height, out of my area of knowledge. This guy helps out DRN quite a bit as well.....I can't seem to remember his name.....I think I saw it around this page somewhere......
 

Jeremy Wilkey

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#9
Spring rates seem to be covered. I'm going to just say that if you heat the lower seal carrier you will typicaly not damage the bushings.
Regards,
Jer