"Swoosh" sound from forks

My forks have begun to sound strange. When pressing them down or letting them up the fluid inside sounds "schwooshh", a sort of sucking fluid and air sound, like there could be water inside or something. I haven't been out in rain or washed it, so no water could have entered from outside.

The damping effect seems okej. Maybe a bit to soft. During the winter I switched the old dust sealer that was on when I bought the bike last autumn to new ones. The old ones were really bad and had cracks in them. Before putting on the new ones I cleaned the area up. The metal clip ring inside had begun to rust, so I tried, as gently as I could, to remove all rust, etc. without scratching the inner fork. I have planned to take them apart completely next winter.

What could this "swoosh" sound mean?
Is it okej to ride with until next winter?

I really don't feel like taking the forks apart at the beginning of the bike season. If I do, I probably end up doing it completely and fix everything at the same time...

/M

you can check the oil level, maybe they are low

If bike has fork oil drain screws, would drain and refill to factory specs.

I think I'll change the oil at least. The whole strip down procedure will have to wait until the winter. As long as there is no leak...

The Haynes manual says it should be SAE 15. I bought SAE 10, since it was the only fork oil for motorbikes they had close to 15. Could this thinner oil do any harm or leak?

I've heard that some people use engine oil as well. Any one tried that? Any opinions?

/Martin

My kz750 factory manual calls for SAE 10. Thats what I used on my fork rebuild a month ago and it seems to be working fine

the only differace the lighter oil should do is make the shock feel softer, not as much resistance from the oil in the dampening effect, you can pull the top cap off and check the oil with a long rod, nothing else to take apart

Are the forks air adjustable ? Possibly to much air pressure and not enough Fork oil,

Air adjustable? Good question. I don't know.

I only have the Haynes manual for the models up to 1976, and mine is from -78. In the manual it shows a different type than mine. In the manual the fork has an top Allen bolt. My forks have a inverted bolt head lowered in the top of the fork. Everything else seems the same. There are small draining bolts on the side at the end.

I had better add a photo...

Anyone knows of these kind of forks?
What is air adjustment?

The old manual says 184-194 cc of oil, but that is for the -76 model. Anyone knows what it should be in z650 B2 -78?

By the way, I think I will go with the SAE 10 fork oil, then. Thanks.

M

OKej, so I replaced the oil in the forks, each at the time. No problems at all. Really a piece of cake.

The level of oil was just on the minimum side, 1,85 dl in each of them.

When changing the oil, I unscrewed the top bolt and the drain screw. I drained the fork, letting the wheel turning at side, pumping a few times. After nothing else came out, I filled the fork up with 1,90 dl. Finally I put the top bolt back. Did the same on the other side.

When testing the forks by pumping them, I still have this sound. Like you are pumping air into the oil.

M

Could the sound be due to air being pressed out and sucked in through the oil seals?

When changing the dust protection, I also cleaned a bit around the circlip. It had some corrosion around it. I used a screwdriver to mock around and then blowed the loose particles away. Could some of the particles have passed trhough the sealer and caused a leak for air to pass? But then I should have bigger oil leak, wouldn't I? Now there is only an barely visible mark of oil coming through the dust. Normal or not normal?

M

Found an intresting article - "The secret world of fork oil"

"Fork and shock oil are two different animals. The oil inside the shock is completely air free, under 300 pounds of pressure and heated to 300 degrees Fahrenheit.

Fork oil is blended to lubricate and damp under less pressure and heat. Since the oil is contained in the same tube as the air, fork oil includes anti-foaming agents. Even if it wasn't a lighter oil, shock oil would immediately aerate and compromise the damping."

www.motocrossactionmag.com/ME2/dirmod.as...40CF833A439ACD16632F

Maybe this is what my problem is about - that foam has been built up/being building up and is sounding when pumping the forks.

M

ANyone knows rthe factory specs for kz650 B2 -78 regarding fork oil level?

Only have a manual for older z 650 up to -76, which says 185-193 cc (dl)


M