Ok,,, I'm stumped on my forks issue

I recently had to replace both fork seals on my 04 YZ450F due to excessive leakage. I followed the manual and I have rebuilt many forks for street bikes but I have never run into an issue like this. It seems the forks lock up when setting overnight and need to be freed up or they will not collapse at all.

I have checked all of the seals, bushings, etc and everything looks great but I still have the same issue. My questions are, do you guys have any idea as to what the issue could be? Also, I have gotten many different answers as to how much fork oil to put in each fork. I had one dealer tell me 6.9 ML, another dealer told me 650cc's and another dealer told me 700cc's.

Could my problems be result of too much/little fork oil? I'm also using the Bel Ray 7wt fork oil. Any help is appreciated.

Thanks,

I have always measured fork oil level from the top of the fork tube with the fork fully compressed (spring out) at 100mm. What that is volume wise I have no idea.

more than likely the seals are a little tight,it'll break in. i measure my oil from the top also. fill the fully compressed tube(without the springs) all the way to the top(like overflowing almost to allow the air spaces to fill)) pump the rod (not the tube ) up and down no more than 6" slowly about 10 times. then fill to a level anywhere from 3 1/2" to 5" from the top. i run mine at 4" but 4 1/2" is typical :naughty: my forks are 46's and takes about 1 1/4 qts to do them both. 48's might take a little more. thinkin' about it if you didn't fill the tube all the way you may not of got any oil between the tubes to the seals. it should find its way there eventually. :naughty:

Measuring the oil height as the guys have said is the only correct way to fill the fork. Knowing its capacity is nice, because you can get a good idea of how much oil to buy, but suppose you don't get as much oil out of one side as the other? If you set the oil to a certain height within the specified range, you'll be better off.

When you fill the fork, the manual makes a point to stress that the fork and damper need to be fully compressed, and that the fork must be filled initially full enough to get oil down the row of holes near the top of the inner tube, so that the upper bearing will be properly lubed. This requires filling the fork nearly full and then pumping the fork leg first, then the damper, to work the oil in. You will usually have to add more after the innards fill up. Could this be something you overlooked?

I did just as ncmountainman stated by filling the fork while the inner and outer tube were compressed. I then pumped the damper 10 times on each fork or until I didn't hear any air(gurgeling noise) in the damper. at this point I then continued to ad fork oil until I had 650cc as instructed by my local dealer which puts the oil level up in the outer tube with the forks extended and the spring installed. I'm really stumped on this and I hope ncmountainman is right in saying the seals will break in.

You need to look in your manual my friend and do what it tells you. The correct waty to go is distance from the top of the tube with no spring and the forks compressed. The manual will give you a guideline on what the acceptable range is. If you do your own oil changes frequently you should either invest in a fork oil tool or create a makeshift one from a turkey baster and fuel line.

You have way to much oil in that fork by the sounds of it. Run 110 mm from the top of the outer fork tube with it fully compressed and without the spring. Thats just a starting point.

yz007f

I just wanted to thank everyone for their posts. My forks are now properly filled and working like a champ.

Thanks again!

so what was it, too full ?

Yep. I measured each fork and in CC terms, they were over filled by about 300 CC's each.

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