is it wise to park a motorcycle outside in the rain with the covers on? why not?

Shouldn't hurt anything, only thing I would be worried about is rust on exposed metal such as the chain. could always give a light coat of wd 40 on the metal. Always did that on my racing equipment after I washed it prevents rust pretty well.

Mine spends all summer outside under a cover and it looks like new 

if my bike been in the rain, is there anything i should do? like drying what parts of the bike so it wont rust or how do i prevent it from rusting. is there a spary i need to buy?

Bikes are made to take the rain just like a car... You should pay special attention to the chain, sprockets and electrical when storing outside... other than that... the GS is one tuff ride. Some times I have gotten lazy and left the bike sit out in the rain (more than once)... there are no ill effects... My GS is a 95 and looks better than some 2005's I have seen...

Just care for your GS as you would like it to care for you  Be nice, give it a full detail 1-2 times a year and keep her fairly clean in between that time and your GS can look great for years to come 

Another good idea is to ensure you keep your bike parked on asphalt, a slab of concrete or a long block of wood and kick stand block if in the grass.  If in the grass and you don't have a block, move the bike forward and back from time to time to ensure your tires don't sit in soft wet grass/mud in just one spot for the entire season.  I'm confident that one season sitting won't hurt, but if you try to get long life out of your tires, or your budget forces you to try and get a long life, every little bit helps.   

Plus trying to start it once a week and running it for 10-15 minutes will help you from having to do a full carb cleaning when the weather gets better.  Also good for the battery if your charger got wet outside because the cover ties couldn't withstand the fierce winds.   

Either way Mate, Happy riding.   

thanks for the information i was so worried that something happen if it left it out in the rain like right now...but after reading your replies i feel a bit better.

As long as you keep riding it, I wouldn't worry.  My bike has been sitting on my driveway (under a bike cover) for some weeks now.  What with rain and snow storms, the exposed part of the front brake rotor has developed some surface rust.

A little bit of rust on the rotor will be taken care of just by riding the bike and making a few stops.  When it starts to thicken up ... well ... I might take an extra rust removal step of some kind when I start riding it again.

If it's going to sit a while I'd pull the battery and put it on a tender.

Make sure you give it a good once over when you uncover it again for a ride.

Mine sat in the rain for 3 weeks when my cover was stolen, no ill effects. Just a little more rusty chain.

I wipe the chromed fork tube dry if it's wet ,wouldn't want any oxidation to develop there ,bad mojo