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Discussion Starter #1
i got a 1983 Kawasaki kz440 ltd it has those front forks that you can put air in. do I have to always have to have air in these? anyway what psi should I maintain in them? how much is too much or not enough?
 

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I wonder if yours is an OEM setup or aftermarket? There was a trend in the 70's and 80's to drill and tap fork caps to convert them into air forks. Be very careful adding air as you can blow out your fork seals quite easily if you add air with a compressor. They recommend using a hand pump and not to use an ordinary tire pressure gage. The pressures needed are generally very low, like 5 to 10 pounds and need to match side to side exactly, so you need a low pressure gage like the ATV's use.

Another note, to work properly the amount of oil in each fork leg must be identical. If in doubt, drain it out and add the exact same amount to each fork leg.
 

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My 81 GPZ550 has air forks. On the surface it sounds like a good idea, in practice, not so good. First the square inch area the pressure has to work on is very small limiting effectiveness. Second, as you add air the back side of the seal is pressurized increasing sticktion. Better to tune with proper spring rate and improve damping with cartridge emulators. One small advantage of air forks, and this is just a crude crutch, is that a leaking seal may be cured with the addition of air pressure pushing the seal lip harder against the fork tube.
 

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My 84 ZN1100 also has air forks but when I looked at Partzilla, it does not show air forks for the A1 or A2 KZ440.
I just went back and had a 2nd look and I see that the A3 and A4 models did come with air forks so the OP's KZ440 would have come with factory air forks.

I agree with 1981GPZ550 that air forks are of limited use. Without air they will function fine. Oh and another downside to air forks is that if you do use an air compressor without an air dryer, it will add wet air to your forks. This will end up rusting the components near the top like the metal spacer tube, and this rust will eventually flake off and end up in your fork oil. Ask me how I know this.
 

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Discussion Starter #5
my air shocks are factory. right now the bike is in the shop getting the front seals replaced one is leaking & the dust boots are missing. after I get the bike home I would like to use some air pressure in them just the lowest figure I can for a little stiffness. just wanted to hear some suggestions on psi..... I had a small pump for these & will get another one..... this bike has only 850 miles on it. it sat in a garage covered for over 30 years.....
 

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Wow, with only 850 miles, you got yourself a little gem.

As GPZ550 points out, you will get extra undesirable stiffness from the air induced "sticktion" and some from the air pressure itself. Sticktion is the added friction coming from your pressurized fork seals. This means more force is required in order to get your forks to start to move. This may mean you notice very small bumps and ripples in the road more than you would without air.

Your best bet is to try it with and without air to see what you like best. You can also experiment with different fork oil, different pre-load spacers and the best option would be some aftermarket progressive rate springs.
 

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Discussion Starter #7
well the shocks were a little bumpy before, probably they were low on oil. when I get the bike back they probably will be ok & I will forget about air pressure.
 

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Discussion Starter #8
the garage said my front fork tubes are slightly pitted & they will polish them & they said they should be ok. I understand this is a common problem? I don't understand why they would pit seeing they have a film of oil on them. anyway the bike should be ready this week. new tubes are expensive & they said not necessary. I hope this doesn't cause problems In the future. has anybody here had this issue & is the bike ok or did it cause leakage down the road......
 

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The wipers on the fork seals and the dust caps are quite effective in removing oil from the exposed part of your forks. In sitting unused for 30 years, any thin layer of oil on the tubes may have been insufficient to protect it from rust that would lead to pitting. Sand or small rocks hitting the tubes while riding can give rust a place to start. But with only 850 miles you have to wonder how any amount of dirt hit those tubes.
 

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Discussion Starter #10
The wipers on the fork seals and the dust caps are quite effective in removing oil from the exposed part of your forks. In sitting unused for 30 years, any thin layer of oil on the tubes may have been insufficient to protect it from rust that would lead to pitting. Sand or small rocks hitting the tubes while riding can give rust a place to start. But with only 850 miles you have to wonder how any amount of dirt hit those tubes.
it was probably corrosion but dam if I can see anything wrong they look like new to me. I guess you have to really look to notice this...
 

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The only real issue is if the pitting is enough to catch on the seal lip and wear the lip out quickly. If you cannot see the pitting easily, it probably won't be an issue.
 

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I have owned a Z550A1 ( with air forks) and now have GPz550H2 also with air. The only difference is the GPz legs are connected so equalise pressure. My advice is max 11psi as a good compromise . I prefer the top end Of the recommended pressure spec (7-11)to try and mitigate fork dive. Tried other settings but for me and my riding style, 11 psi seems to feel best. FYI nothing over 30 psi unless you want to blow you seals. If you run with no air, likely under heavy braking you will bottom our suspension and nut your front mudguard with the exhausts Etc.
 

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Also meant to say, I use a mini hand pump ( used for mountain bike Forks). This works well and no risk of over pressurising.
 
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