Topic: my shocks suck... literally

[Mr.D]

I just noticed today that one of the shocks on my CB550F is making a sound like sucking air when I press down on the bike and it springs back up. It never made that sound before. Is this caused by a worn seal or something? Do I need to replace it?

[CBGhia]

It sounds like you have blown shocks.  If they are the stock shocks, I don't think you can really rebuild them. 
If you like handling, then get some Hagon or Icon shocks.  Otherwise, there are a lot of repops of the stock shocks out there for pretty cheap.

[Bodi]

Shocks do make a sucking sort of sound when moving. The oil has to go through some small holes, this produces the damping action, and a lot of turbulent flow that can be heard. If you're sure it's a new sound maybe they have leaked oil and should be replaced.
If you remove the springs you can feel the damping action when you push the piston in and out, it should be harder to extend than compress. There are simple tools available to compress the springs or you can try two ratchet straps looped through the coils on opposite sides.

[Mr.D]

Thanks guys. I think it probably is an issue of the oil has leaked out. What's going to be the difference between replacing these with reproductions like the ones on 4into1, and the Hagon or Icon shocks that GBGhia mentioned?

[low-side]

Cheapies will have similar damping as the originals (poor), and a spring rate that is likely too heavy.  Glorified pogo sticks.  Hagon, Ikon, etc will have much more sophisticated damping and the company will usually be able to recommend a spring rate suited to you, the bike, and how you use it.  It will be a revelation if you've never ridden your bike with good shocks before.  Well worth the extra coin.