Help replacing 08 yz450f fork seals

14 replies to this topic
  • mxfamilyx4

Posted August 29, 2010 - 11:56 AM


Going to tackle the job of replacing both fork seals on my yz450f. Looking for some info as far as how much fork oil do I need to replace for each fork and anything else I might need other than the fork seals? Any help on this matter would be appreciated! Thank in advance.

  • D-K

Posted August 29, 2010 - 12:32 PM


Well you can always check out this step by step guide I made:



  • sacfelix

Posted August 29, 2010 - 12:33 PM


I have an 06 YZ450 and I put 340ml in the outers but the standard oil amount is 355ml. The fork oil level can be adjusted from 300ml-380ml depending on your specific needs. When ever I change my fork seals I also change out the dust seals. I always use OEM seals and wipers. Its handy to have some Race Tech seal grease on hand as well. You will also need a 49mm fork cap wrench to break the caps loose in the fork tubes. You can loosen these while the forks are still on the bike (Make sure you loosen the top triple clamp bolts first) as well as the rebound nut on the bottom of the forks. Its's also a good idea to write your clicker settings down and then back out both the comp & Reb clickers before you start taking things apart. Another handy tool to have is a fork seal driver but I seen people make them out of ABS as well. If you decide to change the inner fluid as well you will need the little octogon shaped tool to remove the base valve from the dampner assembly. The standard oil height for the dampner assembly is 145-148mm from top of fully stretched dampner assembly. This is a real easy task and usually takes about an hour to clean and inspect every thing. Good Luck!


Posted August 29, 2010 - 01:17 PM


http://www.thumperta...t=07 fork tools


doing the same on my bike right now. just trying to find some NOK seals.

Edited by STROKEDIESEL, August 29, 2010 - 01:47 PM.

  • Gerry B

Posted August 29, 2010 - 10:14 PM


Dont forget to change out the bushings.


Posted September 04, 2010 - 07:18 PM


finally got my tools and parts in today. can anybody tell me how many quarts i need of oil to complete this job? not fluent in the metric measuring system thanks

btw i am doing both sides inner and outer chambers!!!

  • grayracer513

Posted September 04, 2010 - 07:44 PM


That info is in the manual, which you are going to need in order to do this job right.

You'll need two quarts. Be sure you understand the bleed process:


Another confusing point in the manual is the part regarding a gap between the rod jam nut and the rebound adjuster:


1cc (or milliliter) = 0.0338 US liquid ounce

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Posted September 04, 2010 - 08:14 PM


thanks gray!!! i've got the yamaha paper manual and i saw the oil amount for the outers but probably over looked the inner amount. i plan to re read it but was just looking for a rough estimate on how many bottles to grab while at the shop so i wasnt short right in the middle of it. i also have a ratio rite and another oil measuring device. might go to a feed store and pick up a big horse syringe so i dont spill filling the outers.

thanks again


Posted September 04, 2010 - 08:28 PM


when i read it about a week ago this is what i understood:

tighten jam nut finger tight.
slip in tube(forget its name right now)
tighten damper and torque to spec.
check gap if its within limits you are ok.

ive also watched a video on rocky mt atv for the bleed process. seems pretty straight forward.

ill post more if i run into a snag.

  • grayracer513

Posted September 04, 2010 - 08:32 PM


when i read it about a week ago this is what i understood:...

You understood it wrong. There is no gap once the jam nut is torqued. Re-read my post on this.


Posted September 04, 2010 - 08:37 PM


You understood it wrong. There is no gap once the jam nut is torqued. Re-read my post on this.

awesome thankyou ill take pics pre disassembly and after reinstall.

  • D-K

Posted September 05, 2010 - 12:22 PM


Follow the link I posted and it all becomes clear:thumbsup:

  • grayracer513

Posted September 05, 2010 - 01:33 PM


Follow the link I posted and it all becomes clear:thumbsup:

The link you posted was for Showa forks. They are close to the same as KYB, but there are some important details that differ.


Posted September 05, 2010 - 07:21 PM


got one of them dis assembled last night in about 15 minutes..i was taking my time and checking things out. looks pretty straight forward. i do have some questions that i thought of last night that i will post up probably tomorrow.

btw everything looks perfect!!!! with the exception of the leaking fork seal.


Posted September 18, 2010 - 03:14 PM


well i finally got around to doing both sides. i had been very busy as of late. was a much easier process than the book makes it out to be which is written terrible btw. can handle my own with a wrench but the whole fork thing was something i had never done before. HIGHLY recommend anyone on the fence of paying someone else or doing it yourself to just go ahead and do it yourself. i did the second side in about a half hour and was cleaning as i went. the next go around i replace a few other things i didnt this time. thanks for the help all.

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