81 650CSR Front Fork Help!

So I decided to throw some fork oil in my forks yesterday, got them all filled up the the proper level, and filled up to the proper PSI, and they still feel really spongy, as if there is no air pressure or oil in them. I have them at around 10 psi, but not sure how accurate the old car tire gauge is. Either way, there is air pressure, and oil, so I figured there would be at least a bit of stiffness to them. Is there a chance that dirt has clogged any pores in the orifices in the fork itself? Am I doing something wrong? Thanks in advance for the help.

If there's no oil in the fork, it will continue to bounce, just like a car with no shocks.

If there's no air pressure then it will ride a little lower and be a little softer.

So, are you saying the front end is not firm enough for you? If so, then try a heavier weight fork oil. Personally, I regard stiffness as bad, I'd rather have the front tire following the road rather than chattering as it goes over bumps.

What fork oil did you use? Ed

The manual suggested 10w and that's what I used

10W is too light. Unfortunately, the recommendations in the Kawasaki manuals are all over the place on this point. My Kawasaki KZ650 factory Service Manuals recommend 10W, 10W20, and 15W depending on the page in the manual. I use 15W Bel Ray fork oil in my KZ650 and it provides excellent damping. I recommend you drain out the 10W and put in 15W fork oil. Be sure to measure the fork oil level from the top of the fork tube down to the oil with the front wheel raised off the ground, don't just rely on xx number of ounces or cc's when filling. You can use a thin wooden dowel to measure this. Your FSM should provide the correct measurement. Ed

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martin_csr wrote: Just curious... Did you disassemble the forks to clean them? Often times it has never been done & the old oil is a mess.

PS: This page has a pdf manual w color wiring diagrams for the 81 KZ650. jarlef Z650

No I didn't, just drained the old oil and refilled with new stuff....I am guessing the next step is a rebuild?

I would drain the fluid and see if it looks black or otherwise funky. If it looks bad and if your seals are still ok you may want to try flushing it out a couple times with fork oil to see if it clears up; then put in 15W fork oil. If it doesn't clear up there may be nasty thick stuff in there and the need to disassemble to clean. There really isn't anything to rebuild other than replacing the seals at the top of the outer tubes and the dust shields. Ed

If I tear them apart, I am putting in new fork seals just to have the peace of mind that they are new. For the price of a set of seals, its cheap insurance in my opinion.

ShouterVW wrote: If I tear them apart, I am putting in new fork seals just to have the peace of mind that they are new. For the price of a set of seals, its cheap insurance in my opinion.

If you decide to pull it apart absolutely install new seals; new dust shields too. It's too much effort to skimp at that point. Ed

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