Before you actually start cleaning, you should consider how you like your cymbals to sound – because yes, cleaning a cymbal can have an effect on it. A cymbal that's either brand new or has been cleaned is going to sound brighter than one that's seen a lot of use (and hasn't been cleaned regularly).
Is it bad to clean cymbals?
Keeping your cymbals clean is important for their upkeep. Do not play with dirty hands, and when carrying cymbals, use two hands on the perimeter of the cymbal to avoid fingerprints. Dirt and spills should be removed immediately with warm water and soap.
Do cymbals sound better with age?
In short, yes. Cymbals sound better with age. As cymbals age, they produce a dark and mellow sound, compared to the bright and loud sound on newer cymbals. And many drummers prefer the dark and mellow sound of an aged cymbal.