I agree with Sloweddy: back in the days of brushed RC motors, I heard of/saw this method countless times: but it had specific limits. 1) it works best on sealed can brushed motors, the softer material commonly used in the brushes of rebuildable motors absorb water. 2) you use a fraction of the recommended voltage for the break-in. 3) you COMPLETELY dry and lube the motor afterwards (IE heat gun, alcohol, etc.). 4) you cannot use the water method on ball bearing motors (unless you enjoy dismantling and lubing tiny bearings!).
It works as a break-in procedure under certain conditions, but I would not recommend it for cleaning. Please guys, if the brushed motor in your airsoft is that bad, just take it apart and clean it properly. There is a reason why RC shops keep ample stock of motor cleaners
