2002 yz426...fork fluid amount and wt??

i'm working on my buddies 2002 yz426. he needs the front susp. stiffened up...but i don't have a manual. does someone know what weight oil it uses (stock) and how many cc's? he's about 200lbs. if anyway has any comp. and reb. click suggestions, that would be appreciated also. thanks

Instead of the stock fork oil I used Mobil One synthetic ATF in my friends 426. He is on the wrong side of 300lbs. He liked his forks much better with the atf in them. It was also much less expensive than the stock KYB oil. The weight is slightly thicker, but it works well.

I'll second the mobile 1 atf....well so far Ive had great results with a 50/50 mix of mobile 1 and enzo 01 weight...next time im going to go 100% mobile 1. I definitely noticed a change to the stiffer side...but a better change

People that are over 200lbs need stiffer springs. I did.

Maybe this will give you a good starting point to work with. Looking at the manual for my 02 YZ426 it states “Standard oil level is 135mm (5.31”) extent of adjustment 80-150mm (3.15-5.91 in.) from the top of the outer tube with the inner tube and damper rod fully compressed without spring” The standard rebound setting (screw on top of forks) is 11 clicks out and the standard compression (screw on bottom of fork, under rubber plug) is 10 clicks out. I use 5wt. oil any time I change oil/seals in my forks. Use the oil height to help control the last 3-4” of stroke in the forks. If he has a problem with bottoming out, just continue to add oil in 5-10cc increments until he gets the bottoming resistance he needs, just do not raise the oil level above the 3.15” max. If you still can’t control the bottoming with the oil height, then its time to look at stiffer springs. Just take it one step at a time.

Hope this helps. :cry:


all of that is excatly what i needed. thanks!

but is mobil one atf stand for automatic transmission fluid??

Yup, its like a 7wt. hydro fluid.

yea ditto on the stiffer springs....I went one stiffer

From YDS:

Front: Oil Type Yamaha Suspension Oil "01"

Level / Quantity 130mm (5.1in) / 578cc (19.5us.oz)

Gas or Air Pressure Min~Max Æ

Gas or Air Pressure Standard Æ

Rear: Gas or Air Pressure Min~Max 800~1200kPa (116~174psi)

Gas or Air Pressure Standard 1000kPa (145psi)

The Yamaha oil is about a 5wt. Run the spring rates on the Racetech site for your riding and weight to check that the springs are correct for the bike. Also add about 10-20cc more oil to resist bottoming.

If you try to fix with with just oil, it will be to harsh on the small stuff. I had tried 10wt oil and it was too harsh. Get heavier srpings. I did and it made a big difference. Then I went with 5wt fork oil. I started at the stock height and then add a little oil till I got the bottoming under control. I ended up with about 12cc extra in each leg. It is really great now. The springs keep it up in the stroke and along with the higher oil height, helps bottoming. The light weight oil keeps it pretty plush on the small stuff. I rarely notice anything under 6 inches I guess. And I have hit VERY hard (over jumping) and is soaked that up great.

These guys are correct. Depending on the skill level of the rider (insert - how fast is he) and if he is a motocrosser , the first thing to do is make sure the correct springs are in the forks. Then you can experiement with oil levels to "fine tune" them to his liking.

I run .48 springs, 7 wt oil and level 100mm. I still bottom them a few places on the track but that is not a bad thing as long as your still in control......


How much do you weigh? And what spring do you use on the rear?

My weight?/ LOL It varies ALOT but 205-220 depending on what time of year it is (in other words ask me again tomorrow).

I use a 5.8kg on the rear.

Talking about fork oil, anyone used or heard of PJ1 fork oil?

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