Opinions welcome on when I should change the oil on my Yamaha SR250 Special. It's a standard 4 stroke, single piston engine. My usual garage is in Spain (yes I rode my Spanish bike to London) and they changed the oil before I left. I'm going to change the oil myself this time. Must be due I think. Is 1500 km a sensible distance between changes? And is there a filter I have to change, or just one to clean? Thanking you all in anticipation.