Forks not holding air

So i recently purchased an 82 KZ650 CSR, the forks had no air in them. So my brother filled them and two days later the right fork was empty of all air. There is no sign of oil leaking, so it made me not think it was the seals. But could it still be the seals? Could the valve be bad? I dont know where to begincuz im pretty new when it comes to working with motorcycles.

Check the valve cores where you put air in,any hoses connecting forks

Seals, O ring on tube cap or Schrader valves. Mine don't hold air either but thats a cold weather project for me. You could air up (psi's unknown don't over do it). :laugh: little spit on schrader would show leak. Soapy water easier to check larger area.

I put some air in them, and sprayed some soapy water around the valves, but i didn't see any bubbles or anything.

Have you changed (or at least checked) the fork oil? Maybe one leg has been drained by the PO and not refilled so no oil leak would show. Ed

You can call this the voice of experience or opinion , just take it for what it's worth .
Air assisted forks suck . I mean literally suck the air right out of them even when new .
Air may be the "perfect spring" but if you can't seal the fork it's just as useless as Yamaha anti dive .
Just do the math . You have (for example) a 35mm fork tube x 3.14 = 110 ish mm x 150 mm travel = 16,500 sq cm or area that has to seal while the seal is sliding on the tube . Not going to happen .
If your forks need more spring due to age either mechanically preload them or get newer/better/progressively-wound springs .
Normal adjustment for air forks is to get the bike on the center stand , get the front wheel off the ground and let the air IN by depressing the schraeder valve .
Air assisted forks suck . 30 year old air assisted forks suck dawg bawlz .

YMMV

~kop

kopcicle wrote: You can call this the voice of experience or opinion , just take it for what it's worth .
Air assisted forks suck . I mean literally suck the air right out of them even when new .
Air may be the "perfect spring" but if you can't seal the fork it's just as useless as Yamaha anti dive .
Just do the math . You have (for example) a 35mm fork tube x 3.14 = 110 ish mm x 150 mm travel = 16,500 sq cm or area that has to seal while the seal is sliding on the tube . Not going to happen .
If your forks need more spring due to age either mechanically preload them or get newer/better/progressively-wound springs .
Normal adjustment for air forks is to get the bike on the center stand , get the front wheel off the ground and let the air IN by depressing the schraeder valve .
Air assisted forks suck . 30 year old air assisted forks suck dawg bawlz .

YMMV

~kop

x2 A new set of springs will yield far better ride quality

I'm not trying to defend air forks; my bike doesn't have them so I have no first hand experience. But I do have a question about them. My understanding is that they still use fork oil, and that oil rises inside the upper (inner) fork tube. The air that is added is above that fork oil, so the air itself is never in contact with the fork seals, instead it applies pressure to the fork oil which in turn may be in contact with the fork seals. So the air is trapped between the top of the fork oil and the fork cap. In order for the air to leak out it would need to leak from the top of the upper (inner) fork tube either through the valve or by squeezing past the threads on the valve or fork cap. The only other way it could leak out would be if it pushed the fork oil out past the seals or the drain screw or fork cylinder bolt. So if the schraeder valve and fork cap are properly sealed wouldn't he see fork oil leaking out if the air is leaking past the fork seals? Ed

osage wrote: Seals, O ring on tube cap or Schrader valves. Mine don't hold air either but thats a cold weather project for me. You could air up (psi's unknown don't over do it). :laugh: little spit on schrader would show leak. Soapy water easier to check larger area.

Yes, would inspect the "O ring on tube cap" and replace if necessary.

Before removing the cap, be sure the bike's front end is supported so as not to collapse when the cap is removed, and remember to loosen the top fork tube clamp before trying to unscrew the cap.

Might be difficult to see bubbles in the soapy water test where the suspected leak area isn't submerged.

Another option would be to run without any air pressure inside the forks. And if the suspension is then too soft, replace the fork oil with a heavier weight.

Good Fortune!

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