fork oil seal replacement

I'm planning on replacing the seals and oil in my kz650b forks soon because I have a suspicion the seals are wearing out. I read online about it and people are saying it's a real pain in the ass. Why is that?

blink543 wrote: I'm planning on replacing the seals and oil in my kz650b forks soon because I have a suspicion the seals are wearing out. I read online about it and people are saying it's a real pain in the ass. Why is that?

Suspicion?
If you haven't done it before its a good idea to watch someone do it or follow the manual carefully, especially when filling the oil (if you change the seals , change the oil and clean the internals), Check if the bushes need replacing.
The reason why people are scared because it can be an act balancing the bike (I use a stand under the motor) so it doesn't fall when removing a spring etc.

It also helps to have access to an impact to get that bottom bolt out. Otherwise, you'll need the factory tool or you will need to improvise. The rest is fairly straightforward. The forks themselves are fairly simple.
However, unless they are leaking your suspicions are probably incorrect. Leaky fork seals are fairly obvious...

The first fork can be a bear, but the second one should be easy. The bottom allen bolts can be difficult to remove ---- as mentioned an air impact gun is typically the quickest way to get them out (forks assembled w spring pressure on the inner cylinders). Use an 8mm brake caliper socket or hardened allen socket. A cheap chinese allen tool may get twisted & ruin the bolt heads.

Fork tool. KZR topic w photo by 650ed --- the 650B is probably the same as the C1 .

It's not that the job is particularly difficult. Yeah you need to make or buy a few specialty tool. Don't buy because the tools are simple to make. Yeah you have to support the bike with the forks off but again not difficult. The reason most people don't like to do the job is that it can be rather messy. Even with care fork oil seems to get everywhere.

Does a KZ900 have replaceable bushings? Or are seals, springs, and oil the only replaceable items?

ThatGPzGuy wrote: It also helps to have access to an impact to get that bottom bolt out. Otherwise, you'll need the factory tool or you will need to improvise. The rest is fairly straightforward. The forks themselves are fairly simple.
However, unless they are leaking your suspicions are probably incorrect. Leaky fork seals are fairly obvious...

U mean the bolts that hold that thing that goes through the front tire that holds the speedometer drive on?

There are axle holder clamp bolts or nuts & the axle goes thru the speedo drive unit.
He means the bottom allen bolts on the forks.
You have to remove the axle holders first to gain access to the allen bolts --- aka fork cylinder bolts.

martin_csr wrote: There are the axle holder clamp bolts & the axle goes thru the speedo drive unit.
He means the bottom allen bolts on the forks.
You have to remove the axle holders first to gain access to the allen bolts --- aka fork cylinder bolts.

These won't come off. They are regular thread right? Not reverse?

Bozo wrote:

blink543 wrote: I'm planning on replacing the seals and oil in my kz650b forks soon because I have a suspicion the seals are wearing out. I read online about it and people are saying it's a real pain in the ass. Why is that?

Suspicion?
If you haven't done it before its a good idea to watch someone do it or follow the manual carefully, especially when filling the oil (if you change the seals , change the oil and clean the internals), Check if the bushes need replacing.
The reason why people are scared because it can be an act balancing the bike (I use a stand under the motor) so it doesn't fall when removing a spring etc.

Looking online the bushings for my 78 kz650b don't even exist. I should probably just sell the thing. Parts are getting scarce and aren't being produced.

blink543 wrote:

martin_csr wrote: There are the axle holder clamp bolts & the axle goes thru the speedo drive unit.
He means the bottom allen bolts on the forks.
You have to remove the axle holders first to gain access to the allen bolts --- aka fork cylinder bolts.

These won't come off. They are regular thread right? Not reverse?

Those are your axle nuts. They are normal right hand thread. They are tightened to a pretty fair amount of torque so take a little effort, and the 2 nuts down on the bottom of the forks when tightened clamp the axle nuts and the big axle nut can't be loosened until the smaller clamp nuts are loosened first. However to do fork seals no reason to loosen the big axle nuts, just remove all 4 bolts on the bottom of the two fork legs, the clamps can be removed and the whole wheel just falls down off the forks. Be sure and get a manual before doing any work or you're most likely going to do more damage than good. Fork seals are not hard on the 650, but there is a procedure, just like any other job.

A lot of KZ650 parts are the same as for the KZ1000's so most frame and wheel parts are not hard to come by. I did the fork seals on my KZ650B1 when I got it, it was pretty easy really, particularly with an air wrench to crack the Allen bolts in the bottom of the legs. Once you drop the front wheel you will see them in the center bottom of the fork leg. As someone else said, make sure you undo these with the spring pressure on. The air wrench is the key, otherwise the inners will turn and while there are special tools and a makeshift way using a whittled down broom handle that they show in the Haynes manuals, the air wrench is the way to go. I didn't find the seals hard to remove.

One thing to be careful of is the bike coming forward off the center stand while you are doing the job, that made things exciting if I remember . I'm doing mine on my KZ1000 in the next few days, I'm going to hook my engine hoist up to lift the front, so that can't happen.

If you get a manual so you get an overview of what you are doing it's really a pretty easy job, just make sure you have the bike supported well and take your time. It's a good idea to remove your gas tank to avoid that getting damaged when working top sides on the fork caps, depending on your bars you usually have to move them out of the way.