Hello all. I looked outside at my bike today and noticed that it had been leaking some oil. After a good inspection I discovered that the source of the leak was behind the front small sprocket. I took this off and started up the bike. After about 30seconds oil starts pissing out of the output shaft. I assume that the output shaft oil seal has gone, and needs replacing? Is this something that can be replaced myself from the outside? (bike is a 1997 Kawasaki ZZR-250). If so how is this done? Also, just a silly question. Does the gearbox on a ZZR-250 use the engine oil or its own oil reservoir via a drain/filler plug as on a car?