With the bike being stood there may be a good amount of water vapour/condensation around inside the engine and in the engine oil.I take it you haven't changed the engine oil yet?
Check the oil level in the bike,
http://www.pdsrecording.site90.com/cxgl500/OilChange.htm
and for now top it up if it needs it.Use any old engine oil for this e.g 20w50 cheap mineral oil if you have it around but standard 10w40/15w40 will do.
Run the engine up to the thermostat opening running temp.You can tell when this is by touching the Chrome coolant pipe on the side of the engine.It will get warm when the coolant starts to flow after the thermostat has opened.
See how it does.I suspect all it needs is this and then to change the oil and filter and then give it a good ride.
If you want,and I suggest you do this, you can clean out the Air-box by taking the Filter out and pouring a couple of kettles of boiled water in there with the plugs out of those drain pipes.Then dry up with some Toilet tissue inside the box.
Once you've done the above it may still put a little out of the pipes for a while until it clears.
Does the engine itself sound ok e.g not too noisy?
