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Yama/cat

Fork oil

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Can anyone tell me how to properly pour the fork oil in to the forks how much in with the spring ie inner tube and then the outer tube?I have two bikes I'm changing the fork seals on 09 yz450f and a 98 yz400f and if anyone knows the proper volume and can I use a fork oil level tool on these two or do I need to use a measuring cup?

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With the spring and top cap removed, collapse both the damper rod and main tubes. Fill to near the top and then slowly work the damper several strokes until you get the air worked out. Then fill to a level between 85-130 mm from the top. Lower oil levels give a plusher ride, but too low leads to foaming and fade. Start with 100-110. Any piece of wire or such will work as a level gauge.

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Missed the '09.  The previous instructions were for '98-'04 models only.

 

The '06-'09 fork uses measured oil levels in the outer chamber as noted.  The range is listed as 300-375cc in each side, with 350 being called the standard amount.  I use 325cc. 

 

The inner cartridges do not necessarily need to be disturbed during a seal replacement if you don't open them, but an oil change won't hurt anything, either.  It's a bit more complicated to describe, but not such a hard thing to do (read both posts):

 

http://www.thumpertalk.com/topic/737910-smart-performance-inner-cartridge-bleed-method/page-2?tru=GckYa#entry7613090

 

http://www.thumpertalk.com/topic/680824-base-bolt-jam-nut-clearance-06-yz-450-fork/?tru=GckWZ#entry6860151

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I have watched the videos of rocky mountain atv/mc they seem to be very good. Now just to figure out what style of forks for sure and change them out. Any pointers could help. Thanks

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The '98 is a 46mm KYB "open bath" or cartridge fork.

 

The '09 is the 48mm KYB "SSS" "twin chamber" fork.

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I have watched the videos of rocky mountain atv/mc they seem to be very good. Now just to figure out what style of forks for sure and change them out. Any pointers could help. Thanks

I agree I just changed my seals this past Saturday on my 2007 yz450 and it was a breeze.  For the 1st leg I kind of just followed along with the rocky mountian video step by step, took me about 45 minutes for the first one.  The second leg took me about 30 minutes tops.  Much easier than the older style cartridge forks IMO.

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