1983 KZ550-F1 (Spectre 550) Air Fork Pressure

While this is something that can be answered in "RTFM", I won't be able to get one until next week. Anyway, I'm looking for someone who might have the acceptable pressure range for the '83 KZ550-F1. Doing a google search I find everything from "Don't exceed 10psi" to "yeah, don't go over 36". That's a pretty big range. The sticker on the fork itself just says to read the manual, that's useful.

I'm already aware there's a good chance the seals in the thing are rubbish and probably need replaced, that's not a big deal. It'd be nice to see if by chance they're still holding something first though. As-is, the fork compresses and rebounds fine without any bouncing but it's just way way way too soft, I'm maybe 130 soaking wet and even I'm thinking this thing is too soft, it'd be bottoming out with anyone heavier.

I don't know about the 550, but on the 81 650 the useable range is around 7.5 - 14 psi or thereabouts (the max listed on the forks is 36psi). You should use a low pressure air gauge to check the psi (not a standard tire gauge). Also, it would be good to use an air pump with air fitting that doesn't loose pressure when connecting & disconnecting it. otherwise, it's almost impossible to adjust the air pressure in the forks. I've heard of a Harley pump for airing up the forks. Some guys recommend installing new progressive springs & eschew adjusting the air. Also, if the manual recommends 10W fork oil, you might want to go with 15W or something.

If you follow the links in my signature, there are several online manuals. Some don't cover the Spectre, (the Spectre comes in the shaft-drive Kz550 FSM, which I don't have) but if you look at the fork air for the Kz550C, it'll give you an idea of where to start. Never exceed 12 Psi as a working pressure with forks extended (wheel off the ground). 36 psi is way way too much as a working pressure. It is the maximum limit for a brief moment while inflating the forks. But even then it's too much. You don't need to go above 20 to get the forks into their working range of 7 to 12 psi (on some models). The Kz550C Ltd. has 10 psi as the upper limit.

I don't use much pressure if at all. It makes the forks have more "stiction". I go with stiffer springs and little to no air (as Martin mentioned).

You can stiffen it up yourself for almost no money by cutting the springs down and inserting a PVC spacer.

The air pressure doesn't stiffen them up very much anyway. It'll raise the front end by maybe one inch or so near the max pressure, but the rate will still feel squishy.

Here's the page from the FSM (white base manual) for the chain-drive Ltd model (Kz550C). Open it on a new tab/page to see it full size.

www.amazon.com/gp/product/B000GZPGCQ/ref...07_s00?ie=UTF8&psc=1

Here's the pump I got for the suspension on my bike.

Works well and holds air when disconnecting from teh fitting

loudhvx wrote: You can stiffen it up yourself for almost no money by cutting the springs down and inserting a PVC spacer.

Going full mountain bike here with volume reducers. I'll probably end up trying this out. As-is, I'm maybe 130 pounds soaking wet and nearly bottoming out over speed bumps at low speeds (sub-10 MPH). Also need to replace the seals, they're completely shot as expected.

loudhvx wrote: Some don't cover the Spectre, (the Spectre comes in the shaft-drive Kz550 FSM, which I don't have)...

No worries. Come pay day I'm planning on buying the shaft manual and I'll scan it no problem. May as well make use of the fancy duplex scanner.