KZ fork oil weight?

[twistngrip]

I have a '82 KZ550 LTD. I recently changed the fork oil. The book calls for 5w-20 motor oil which seems a little outdated. My local Kawasaki dealer advised to put 15w Belray fork oil in, which I did. The forks seem really harsh now. They are noticeably worse than before. I am trying to decide whether to try 5 or 10w instead. Has anyone been through this before and if so, what works the best? Thanks. Tried the search and couldn't find anything that answers my question.

[oldcoldankles]

The fork oil specified for my 1983 KZ550 is 10W. Try that first.

[twistngrip]

Ok Ankles,

Thanks for the input. I kind of thought 5w would be going too far. Have you experimented with different weights? If so, I would be interested to know how much difference the changes make. Also, I am operating in a very warm climate (AZ) so I kind of thought 5w would be too thin in the summer.

[Lawn Masters]

you know you've got an old bike when the book says to use motor oil.

I'm known to run 10W or 15W oil in my forks. I dont care for lighter stuff, but do a lot of harder riding too, so keep that in mind.

Right now I just buy harley heavy weight oil and run that. its worked well for me so far, and I'm happy, but this is me too.

[twistngrip]

All I know is this 15w that I put in is more harsh than what was in there before. This bike was parked in the corner of someone's garage for years upon years, so I wouldn't be surprised if what was in there before was from the factory. The only way to go is lighter than the 15, but I wasn't sure what to try. You have me convinced that the 10w is the way to go. The way it is now, when I ride down a perfectly flat road I can feel every imperfection in the roadway. Thanks.

[twistngrip]

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[Nate]

I first ran 10W in my SR and felt that was too light. I'm a heavier guy and if I hit a washboard on gravel road the front would really chatter and I think the oil would get foamed up as it was squirrely for the next couple of miles. I put 15W in and those problems seemed to go away (could've been brand related as well). Experiment to see what works best for you. Some have discussed mixing weights as a way to acheive a "halfway" weight but others advise against it.

[zoro]

Originally Posted by oldcoldankles

The fork oil specified for my 1983 KZ550 is 10W. Try that first.

Old Coldancles is right! My 1979 Kawasaki service manual specifies 10w for the fork oil and my bike is way heavier than the 550. I used Belray fork oil for its anti foaming properties. Heres whats most important,To maintain the proper "harmonics" and equal dampening in each tube,you must carefully fill each tube to its specified fill level! Improper levels will result in uneven dampening and "headshake" because of improper dampening balance and harmonics at speed......."Bad Juju"! Go with the 10w and follow the filling and fill level check procedures and specs!

[twistngrip]

I did do the refill very meticulously to the prescribed level. Both sides are identical and the air pressure is the same (8.5psi). I won't have time to do the change for a while but when I do I'll post the result. It sounds like 10w is the way to go.

[herk]

Did you service the forks or just do an oil change?

[twistngrip]

Just a drain and refill.

[herk]

So.... Did you look at the old oil. What was its conditon. What oil did you ad. Did you check the level in each fork afterwards....

[twistngrip]

The old oil looked in great shape. I refilled with Belray 15w and was very meticulous with the oil levels. I am in Phoenix, so this summer it was obviously very hot. In these conditions, the 15w felt better than in winter. So, I never switched to 10w as I intended to do. Now I have a buyer for the bike, so I'm not going to be able to see what the difference would have been.

[wdhewson]

Gents: I've used 5W30 or 5W20 or ATF in all my forks for years. I'm in Canada, so the 5C degree riding days aren't too stiff in the fork. In Pheonix I'd go for the 5W30 for a supple and compliant fork. At one point in my life I was very familiar with the Monroe shock oil specifications, low viscosity, anti-wear, low foam, and heat resistant.

[Polar_Bus]

10W is is good all around viscosity for most bikes. If you are 200+ lbs, or really "crank it up", then 15W might perform better.

Nothin' like the smell of 30 year old original fork oil. Kinda' smells like the $hithouse on a tuna boat.....

[wdhewson]

Tuna boat. Are you old enough to remember that we used to accuse the fishing nation of Japan of using fish oils in their shocks, and that the old FVQ which meant Full Variable Quality, got restated as Fade Very Quickly. I have some Showa rear shocks from a KZ750 that are so clever, and so good that it is unbeliveable. Made when Japan set the world's quality standards.