ok firstly dont worry about it the bikeis air cooled only so its not that your head gasket is gone and the water is getting in there that way.The main reason it gets like this is from short runs so basically the engine doesnt get a chance to warm up properly and this causes condesnsation inside the engine which mixes with the oil and makes the creamy grey/brown goo you can see.one trick to clear a sight glass of the goo is to heat it with a hairdryer from the outsideit will eventually go away.but you cant really stop it from doing it unless you give it a few good runs.
adam bike doctor, August 2010
