To air or not to air in the front forks?

[Bolder Biker]

Domino,

I would first flush and change the fluid. Ryan did that on his 550 as well as adding short (3/4" ??) PVC spacers to add some more spring preload. He used 15 weight fork oil. The Suzuki manual said to use a mix of ATF and motor oil (can't remember what weight). I'd go with the fork oil. Ryan's fork was noitceably stiffer and more controlled after the changes.

Joe

When using cut PVC pipe as spacers, I would recommend using a suitably-sized, flat steel washer between the spring and the spacer. The washer will provide a broader contact surface and protect the PVC against point wear.

BB

[Joe Nardy]

Great idea, BB..................

Thanks,
Joe

[silverhorse47]

Don Lob.,
Exellent point re air pressure in forks and the information re longevity helped me.
Thanks.
S.

[Don Lobacz]

You're welcome.

[saaz]

Oh yes..I have had the front fork caps linked for 20 years or so..the parts are available from shock places. Makes it easy to equalise pressures. I also have an S&W mini pump to do fork pressures. I usually run Fornales air rear shocks as well, so it is easier to match performance front and rear.

[opiewontaylor]

I've run the max air pressure (17lbs.)in the forks on my 850 for 14 years, and have never had a seal go bad. I run the maximimum in my Honda xr650 (6 lbs). I weigh 250 lbs, and the forks are way too soft otherwise. Air in the forks does make them less responsive, but really helps cut down on forward brake dive. In my experience, forks that do not have air adjustability, come set up much firmer than the ones that do.

[Anonymous]

I'd do what the other guys say and set up the stiffness etc... without using air. As soon as I messed with the pressure on the forks (the guy who inspected it had the pump and probably didn't even put 5 psi in) the seal on one fork started leaking bad.

[opiewontaylor]

I'd do what the other guys say and set up the stiffness etc... without using air. As soon as I messed with the pressure on the forks (the guy who inspected it had the pump and probably didn't even put 5 psi in) the seal on one fork started leaking bad.

No offense, but if you had a seal leak immediately with 5 lbs of air, the seal is bad in the first place. I have a Clymer manual that states categorically that air pressure, (to a degree of course), is actually beneficial to seal life. To each his own.

[Anonymous]

if your forks were originally equipped with air assist then you need to keep some air in them to help out your seals. they are designed so the air pressure helps them give a squeegy effect keeping the oil inside.

[80gs1000e]

........Do you know if the "anti-friction" teflon-coated bushings have ever been replaced? There are 2 of them in each fork leg (upper/outer and lower/inner), and their function is to prevent friction between the 2 upper and lower parts of the fork as they slide past each other.........

BB

I am confused and can't pinpoint which item you are talking about. Can you see them in this diagram?

[Bolder Biker]

I don't see them on the parts diagram for your bike. On the diagram for my bike (1983 GS750ES) linked below, I believe that they are parts #7 and #10.

http://houseofmotorcycles.bikebandit.com/partsbandit/showschematic.asp?dept_id=715082

BB

[Clone]

If you use fork oil, it is supposed to resist foaming, like ATF. I wouldn't use engine oil mixed with anything. You will always have air in your forks, so the argument to not add pressure is pointless. Without the air your fork wouldn't compress as it would be full of oil. My bike is 21 years old with the original seals, has had between 15 and 20lbs in it all the time and hasn't wrecked the seals. I would definitely drain the old oil and stick in some new 15W fork oil. It will handle much better. When I changed mine, I did it twice. Changed out the old stuff, drove for a week and then drained it again. The oil cleaned out more accumulated crud. It is cheap, only $6 per bottle so the price shouldn't scare you off.

[Dink]

My 1150 85 model has both bushes you refer to , my 82 1100 Kat only has the lower split bush.
Btw you will also need to replace number 15 it is a nylon bush it goes on the damper rod.
Dink

[80gs1000e]

........I did it twice. Changed out the old stuff, drove for a week and then drained it again. The oil cleaned out more accumulated crud. It is cheap, only $6 per bottle so the price shouldn't scare you off.....

Good idea. Thanks.

you will also need to replace number 15 it is a nylon bush it goes on the damper rod.
Dink

When I take them apart, I'll check that out. Any questionable pieces will get swapped out for new. This bike had sat outside for a few years at least before I got it. I lost the auction for the fork pump but I have my eye on another one.