Squishy sounding forks - Sound alright to you?

I just changed the oil in my forks (1978 KZ1000) and I don't like the way it sounds.

Actually, I overfilled them a bit a few weeks ago, and the bike has been sitting. I just used a syringe fork oil tool to suck the excess oil out to the level of 17.4 inches (forks extended on jack with springs out).

Put it all back together and pumped the forks and it sounded like this:



Am I just getting antsy about nothing, or does this sound off?

The soundtrack to an old porno! :laugh:

Seriously, did you have the fork caps off? The oil rushing through the valve on the rods at the bottom of your forks will sound like that. Putting just a little more than is spec'ed out isn't going to be a big deal but the fork action will get stiffer the more you put in there. As long as the oil is covering the tops of the damping rods you are probably fine. What weight oil did you put in there? Are those progressive springs?

2 questions:

What brand and weight fork oil did you use.

Why did you remove the springs when measuring fork oil level? My KZ650 manuals say leave the springs in.

Ed

My manual said to measure with springs out.

I used 15w (don't remember what the brand is).

So you you don't think it sounds abnormal?

DiamondSkyBlue1000 wrote: The soundtrack to an old porno!

:laugh: :laugh: :woohoo: :woohoo: :woohoo: :woohoo: :woohoo:

Man them forks are messed up...that is not right.

4TheKZ1000 wrote:

DiamondSkyBlue1000 wrote: The soundtrack to an old porno!

:laugh: :laugh: :woohoo: :woohoo: :woohoo: :woohoo: :woohoo:

Man them forks are messed up...that is not right.

That's not what I wanted to hear. I'm going on a long ride this weekend.

Any guesses? Perhaps too little oil, causing air to suck through?

It sounds like air going through the damper rods but you can also hear the springs rattle. This is why I'm asking if you did that test with the caps off of the forks.
Did they make that noise before you lowered the fork oil level?

The caps are on.

It made noise like that with more oil in there as well. I think they were sounding like that before I changed the oil too.

I've had this bike for years. Road it like crazy for 4 years, then neglected it for 5 years. Now I've sold my modern bike and gone back to the KZ. I was wondering if the handling had degraded, or if I'm just getting reacquainted with outdated suspension.

I think the seals are good, but I wonder if there might be something else out of sorts?

mattb wrote: ...changed the oil in my forks (1978 KZ1000)...overfilled them a bit a few weeks ago, and the bike has been sitting. I just used a syringe fork oil tool to suck the excess oil out to the level of 17.4 inches (forks extended on jack with springs out)....

650ed wrote: ...Why did you remove the springs when measuring fork oil level? My KZ650 manuals say leave the springs in....

mattb wrote: My manual said to measure with springs out....

The FSM says:
...
3. Install the spring with the smaller diameter end facing down.
4. Refill with 180~188 cc of fresh SAE 10W20 oil.
...
After disassembly and completely dry 180~188 cc

When changing oil (wet) about 160 cc.

Oil level should be 420 mm from top of the inner tube.
And is measured with the front wheel off the ground, and the springs left in their normal position inside the fork tubes.

Good Fortune!

Putting the smaller coils at the bottom will mask more of the spring noise.
Shoulda' replaced the springs with Progressive ones while you had them out. They're inexpensive and I think they are worth it.
I seem to remember that when I rebuilt mine they were noisy at first until all of the air was out of the damper rods.
At the bottom of your springs there is a guide that looks like a specialized washer that keeps the spring centered on the top of the damper rod. Are those in place? It's possible that your springs are rubbing on the inside of the fork tubes and causing that raspy rattle.
My 77 has different damper rods that have a ridge that keeps the spring centered. It also had spacers at the top of springs that aren't shown on the parts diagrams. Are all of yours in place?

I already have Progressive springs in there, though I don't know what rate they are. I assume they are stiffer than stock, but that's just a guess and I don't know anything more than that.

I've got some new fork seals on the way and I'm just going to rebuild them. I'd love to know there was a quick fix, but I may as well just do a quick rebuild and be done with it.

mine squished after the rebuild and fill. just bleed as much air out as you can per manual and ride it. mine went away in less than fifty miles. how much less i dunno but after i rode that far i checked and it was gone.