So I bought a 2010 wr250r months ago. The previous owner said he changed the oil before I bought it. And it actually looked new in the window. No idea if he changed the filter. Anyway about 1k miles (or less) later figured Id change it, breaks, the drive, etc. So after heating it up, draining, putting in a new filter, magnetic plug, and fresh 50/50 blend; I go for a little ride. The oil is starting to look darker/old/dirty already... WHY??? does the system need to be flushed? Maybe it was put through water/ mud. Any insight?