how would these guys come up with a "weird liquid" if they were just hangin' around. was there any evidence of a liquid around the bike or some type of spillage? it's pretty obvious that if you look down the dip stick hole and see sand that it would have to be cleaned out. why are you asking which liquid would do the most damage??? . if there was any contamination in there at all including a "strange liquid", i'd take the clutch cover off and completely clean every component.if there is sand in it i'd also check the transmision out. sorry, but these questions are just a little strange.very "interesting" story if i found anyone f**king with my bike i'd beat them to death with their own shoes! i'd be interested to know how far you chased these arseholes.