Front fork air pressure
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  1. #1
    Seat Tester
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    Front fork air pressure

    What is the proper air pressure for the front forks on a 1986 Kawasaki 454 LTD?Thank you, Ric

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  3. #2
    TurtleWax Taster
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    Air? Isn't there supposed to be oil in those front forks?

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  4. #3
    Just Won't Go Away !
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    It really depends. Most folks find that the ride and handling are best around 8-10 psi. Some folks like it at 12 because they ride aggressively or carry a passenger. Technically the forks can hold up to 36 psi, but that is the burst point when they were brand new, and running the air too high not only makes the ride harsh but it also can blow out the fork seals. I tell folks never to go above 12 psi- if you find that the ride is still too soft or the damping action too quick at 10-12 psi with the stock 10-weight fork oil, I would go to a heavier 15 or 20-weight fork oil and drop the pressure back down to 8psi. Increase it 1 psi at a time until you are happy with the ride. Never, ever use a compressor to adjust the air pressure- just use a hand pump.

    Joey- many motorcycles, including the 1985-88 LTD 454, use compressed air in the upper part of the fork to allow the rider to adjust damping, in the same way the pre-load adjustment allows the rider to adjust how the rear shocks act. The lower part of the fork is identical and holds conventional fork oil, while the upper part of the fork is made air tight, and usually there is a balance tube between the two forks to keep the pressure equal. A simple tire-type air valve either in the balance tube or the fork cap allow the air to be added.
    As the valving on fork dampers have become more sophisticated air assist forks have become less popular, but they were quite common on Japanese bikes in the 1980s and 90s.
    Last edited by DrBob; 09-01-2013 at 07:51 PM.
    You MUST obey the pug dog!


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  6. #4
    Y2K
    Y2K is offline
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    Quote Originally Posted by DrBob View Post

    Joey- many motorcycles, including the 1985-88 LTD 454, use compressed air in the upper part of the fork to allow the rider to adjust damping, in the same way the pre-load adjustment allows the rider to adjust how the rear shocks act. The lower part of the fork is identical and holds conventional fork oil, while the upper part of the fork is made air tight, and usually there is a balance tube between the two forks to keep the pressure equal. A simple tire-type air valve either in the balance tube or the fork cap allow the air to be added.
    As the valving on fork dampers have become more sophisticated air assist forks have become less popular, but they were quite common on Japanese bikes in the 1980s and 90s.
    My 2000 Harley E-Glide has air-forks up front and air shocks on the back, the air valves for both are just behind the right saddlebag lid on the rear fender strut.
    I usually run about 10 psi on the forks and 15 on the shocks ,a little more if I'm riding two up and packed for a road trip.

  7. #5
    TurtleWax Taster
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    I have been schooled. Thanks! Never ran across a bike with that. Or maybe I just didn't pay attention


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  8. #6
    Just Won't Go Away !
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    A lot of small displacement Honda models in the 80s used air assist forks that would run in the 5 psi range. Kawasaki had a few model as did Harley, and there were a handful of models from Yamaha and a couple from Suzuki. Usually it was an effort to get a smoother, less busy ride on the touring version of a model, or to get a 'big bike' ride out of a lightweight motorcycle. I think Harley stopped using them in 2003, as did just about everyone else.

    Some models today, mostly dirt bikes, use pneumatic front forks, which are different from air assist forks. An air assist fork is a conventional fork with a little compressed air to pre-load the spring, where as pneumatic forks use compressed air instead of a fork spring. Not really suitable for on road, but it does shave almost 2 pounds off the sprung weight of a dirt bike, and they reduce the "I think I just broke my wrists" feeling when the front tire has to move vertically very quickly, so I expect they will be more common in higher-end dirt bikes in the coming years.
    Last edited by DrBob; 09-02-2013 at 03:54 PM.
    You MUST obey the pug dog!



 

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