My XJR1300 '07 model has a unusual oil like stain that appears on the engine, have cleaned it off with truck wash but re-appears after a ride,originally just thought it was some baked on road grime eg. tar but now think it is oil. Don't think it head gasket or rocker cover gasket as oil would be spraying out everywhere. Took it to the bike shop and they are 'Baffled!' as to what causes it, funny thing have seen another XJR with the same oil mark. My bike has only done 7000km and just come out of warranty. Oh yeah bike shop checked all bolts, oil cooler lines etc And its only on the outer cylinders, a mate suggested maybe it's oil seeping out of the casting..that I don't know. What do you think ?