Defeating fork air system?

[polkat]

I have another KZ (KZ650) that I rarely post about, as it is in good shape. But I have had problems with the air/oil forks. Even though the seals are good and don't leak, they are usually out of air on one or both sides when I check it. Others I have talked to say that the air/oil system that apparently many manufacturers went to in the early 80's is a poor design, and I have heard of some who defeated the system by adding a spacer
above the spring and not using air at all.

Has anyone here done this, did it work, and what length of spacer did you use?

[StarGate]

Since the forks only hold a small amount of air (volume wise), and it's at a very low pressure (less than 10 psi), simply testing it with a gauge can release all the air and even if that doesn't release it, it will lower the pressure in the fork. Adding a spacer on top of the spring just compresses (preloads the spring) the spring and reduces the amount of travel. You can run your forks with no air but this will take away some of the dampening.

[polkat]

What about adding a little extra oil and no air?

[StarGate]

If you think you're smarter than the engineers that designed these bikes and can re-engineer a better system then be my guest. I wouldn't advise it though.

[polkat]

Nope! I'm no engineer, but it does seem to have it's design faults, and from my doodling on Google, it seems that many manufacturers have backed away from it. But no problem, just courious.

[StarGate]

A lot of designs will become obsolete as technology advances. That's just the nature of it. And there is always the chance that someone will come up with a modification that will improve on a current design. That is one way we make technological advances. I just think that in most cases where people have used spacers or similar ideas and achieved better results, the reason they get better results is because they are working with springs that have compressed over time and no longer meet required specs. So the spacer or whatever they do is just making a worn out spring better than it was. If you're looking for better suspension out of the same system I'd recommend investing in some new Progressive springs for your forks.

[MFolks]

I've read/heard that one way to go would be getting a good set of progressive suspension fork springs and get a set of cartridge emulators from race tech.

[polkat]

I suspect that these springs are original and somewhat compressed, although I haven't measured them yet. Who carries these progressive springs, and can someone explain to me what cartridge emulators are, and the advantages? Thanks!

[MFolks]

Progressive Suspension - Performance Suspension Components for Harley Davidson, Honda, Suzuki, Polaris, Yamaha and Kawasaki sells new fork springs. and Race Tech Suspension sells the cartrige emulators for these older bikes.

[steell]

I wouldn't advise RaceTek cartridge emulators unless you're racing or a glutton for punishment

[Cucco]

excuse me, OT: what is a max pressur for air forks of gpz550??

maybe damage fork seals over 2 bar?

[kawpaul]

Originally Posted by Cucco

excuse me, OT: what is a max pressur for air forks of gpz550??

maybe damage fork seals over 2 bar?

Mine is a 750 but is probably the same and calls for 5.7-8.5 psi. You will have to convert that to bars.

[northernman]

OP I assume the forks are too soft for you, correct?

Why not do the best thing then, and change to pregressive ( or at least heavier) springs.

Very easy to replace.

And while in there, the oil is likely way overdue for a change to, so also do that.

[kopcicle]

Before I take off on the cop bike I place it on the center stand , prop the front wheel in the air extending the forks completely then remove the air valve covers on the forks and just press them once . Most of the time they will suck in a bit of air . Then again I'm not using stock springs or dampening and I agree that emulators are for masochists . Stay near suggested oil levels as just as little as 20cc too much can begin to lock the fork . I recommend the progressive springs and do a whole bunch of reading on possible dampening modifications to your forks before attempting anything . This is one place where I won't offer a suggestion as each rider has his/her own riding style .

~kop

[wdhewson]

Hi. The function of the air is to be a spring, and air is a perfect spring until you get to pressures so high the the air gets close to liquifaction. And that is mega-pressures never to be seen in our forks. Air is also a near mass-less which add to its perfection as a light weight spring. However, if the fork with no extra "air-spring" is too sagged, then a light weight PVC or aluminum spacer of an inch or two is a good replacement for leaving out the "air-spring".