It is standard procedure of almost all of the authorized and non authorized motorcycle service centers to wash your motorcycle during routine servicing.
However this washing can actually be harmful for your motorcycle, here is why:
They wash motorcycles before the service: Quite a few service centers wash motorcycles before the servicing is done. While it cleans out the muck and enables the mechanic to work efficiently, mechanics while servicing the bike leave oil/grease stains on it. Since motorcycles don’t get washed again and the cleaning guy simply uses a cloth to wipe the stain, this results in harmful chemicals spreading to even greater area, which in turn can affect your motorcycles paint.
Cheap quality soap: Majority of the service centers I have seen, use Fena or similar cheap quality detergents, which are meant to wash cloths and not motorcycles. Such harsh detergents are harmful for your motorcycles paint and if you want motorcycle to retain it shine for years to come, avoid them like plague!
Low quality wax/polish: A low quality wax/polish can actually be harmful to your motorcycles paint and can even remove a thin layer of paint, so even if you have to get the motorcycle washed from outside, don’t allow them to use these substandard polishes on your bike. Instead buy a good quality motorcycle/car polish and apply it yourself, it hardly takes 15 minutes to do this!
Same cloth is used on the entire motorcycle: Some of the cleaners at these service centers use the same cloth to clean all the areas of your motorcycle i.e. tank, side panels, rvm, rims, chain cover etc. and then they use the same cloth on the next bike. This means, that poor quality polish is being applied to your motorcycle, using a cloth which was used to clean another motorcycle’s chain cover and rims! To make matters worse, few even have the habit of cleaning the rims first and then the body!
These are just some of the reasons I have stopped getting my motorcycle washed from outside and instead like to do it myself and in a situation I have to get it washed from outside, I normally ask them to not use soap or wax on my motorcycle, which protects it to a certain degree.