Hissing forks!

[pkboxer]

When I push the bike (90/6) off the center stand, I hear air hissing out of the top nuts of the forks.

Questing, is that totally normal? Or is there a valve not opening that is causing air to be "trapped" and getting compressed?

Or does the hissing mean that the top caps aren't sealing all the way?

Thanks

[Kurt in S.A.]

Does your bike have the fork gaiters? There should be hollow locating pin that goes into the lower yoke that mates with a hole in the gaiter. This is where the over pressure is supposed to get out.

Kurt in S.A.

[pkboxer]

Yes, it's gaitered.

I'll have to look at a parts blow up.

Does this make a noise? I'm wondering if I'm getting excess preasure.

[Deleted User 72]

On the center stand the forks drop down from gravity, expanding the gaiters. Off the stand, the forks compress to their sag height, compressing the gaiters which blow the extra air out through the hole described above.

No worries!

[Ken in Oklahoma]

... I'm wondering if I'm getting excess preasure.

That's unlikely I think. There was a fad in the 80's for removing the springs and using a Schrader valve and air as the spring. A '78 parts airhead I bought had that setup front and rear. There were even air pressure gauges to monitor the the air pressures.

The disadvantages I imagine would be increased fork stiction because of the air pressure holding the seals tighter against the fork tubes along with more maintenance fuss.

A possible advantage would be the ability to tune the fork "spring" via quantity of oil in the forks and air pressure. For the rear shocks you could play with the air pressure.

As far as for excessive air pressure damaging the front forks, especially when hitting a major bump, I would think that the excessive air pressure would simply pop out the fork seals, making them an impromptu safety valve.

If I had considered turning that parts bike into a runner I would have removed the air suspension stuff. As it is now the parts bike is a rolling low rider.

I have to think that if air suspension was overall a good idea then we would be seeing it on various competition bikes. Or maybe some of them are using it and nobody told me.


Ken

[mattcfish]

Yes, it's normal to hear the air rushing out of the gaitors when you take it off the stand.

[Motorhead]

I had the hissing top caps replaced the metal ring sels with a rubber O ring