i hate forks...

Forks are easy. The hardest part is finding a way of getting the front off the ground. Only problem you might have is not having a seal driver. I got away without needing one but next time I will source one for sure. Have a look on YouTube if you are unsure of the process and components, plenty of instructional vids showing what needs to be done.
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I know it is for cartridge forks but it is the exact same process except in insides are in separate bits.

 

okay... well i searched long and hard for a solution to the fzr's crappy fork issue, DONT even bother with dreams of nice upsidown forks, there is an easier solution.

first of all seals are a piece of cake.
see the terrible diagram below from some site, of damper rod forks, ignore the emulator for now.

so jack the bike up from under the headers useing a jack and some wood (dont worry, i did this for years without an issue).
with the triple clamp bolts loose, and loosen to the caps. then undo bottom pinch bolts, take the caps off and pour out the oil.
and out will fall the springs and tube (preload spacer).
now to undo the damper rod bolt that secures it to the bottom of the fork outer tube, you will need to unscrew it, whilst holding the damper rod in place with a rounded end wooden broom stick or similar to stop it from spinning with the bolt.
turn the fork upsidown, out will fall the damper rod from the middle of the chrome tube.
remove the dust seals, they just pry off easily.
remove circlip above oil seals.
now use the fork tube to drive the fork seals out of the outer tube. this usually requires a fair bit of force, so dont be scared to get stuck in, sometimes heat helps on the outer tube.
once the seals are out, your chrome tube will have a teflon band at the bottom, the teflon on this will probably be a little bit frayed, get new ones when you get seals from yamaha, or just trim of the frayed edge with a razor if there is plenty of teflon left. you'l get the idea when you see it.

now with all this done, you can reverse the order in which its done... just really have a good think about which order it goes back together... and use the fzr400 service manual somewhere on this site... its exactly the same process.
Use a 10w fork oil, silkolene wins in my books.

 

Now Part II...

The fzr has damper rod forks.
Damper Rod forks are ancient forks that have being around since the conception of telescopic forks (Pre 50's!!).
Damper Rod forks are cheap, and they really stink.
Basically oil flowing through the holes in the damper rod on the compression stroke creates a very harsh, very sharp increase in damping force. You'l feel this as a solid jolt through the handlebars.
As well as this, the units design provides very little rebound damping... which results in endless head wobble on bumpy road... ewwww yuk.

You can improve your damper rod fork with a small device called an emulator, (also called travel control valve, tcv for short).
These Devices provide a better damping character for the compression stroke only, they give a less harsh, but much smoother (NOT SOFTER!!), much better performing damping character. you can see from the above diagram how they fit in the fork. All you need to do is pop them in, and cut your pre-load spacers shorter, but make sure you measure how much spring preload was as standard, and keep that. I think if i remember correctly, i used 31mm emulators. PDS TCV's they were called.

As for rebound damping, the solution that was used on my bike was to braise the rebound bleed holes shut, as there is enough leakage past the damper rod to permit flow on the
rebound stroke, as the seals are pretty frapped usually, this sorts out the rebound stroke.

All the above was carried out on my from forks.... and it had me jumping for joy, the bike felt so much different, so much smoother.
Chuck in some stiffer springs, like - 0.80 kg/cm (compared to stock 0.55 kg/cm, err thats like motorcross bike springs).

Hope all this helps.

Some feel me in if i missed sumthin.

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cya