Give me some ideas people. My trusty BMW R45, which I am trying to get up together to sell, developed an oil leak from the clutch housing a few weeks back. I finally got around to taking it apart this afternoon to remedy this.
My first thought was that it was the input shaft seal on the gearbox as earlier this year I had to rebuild the gearbox following a selector failure. I've removed the gearbox from the bike and now had the thought that it could potentially be the crankshaft output seal. In which case, bugger.
I had hoped that the oil stain inside the clutch housing would make it obvious but it hasn't as there is oil all over the bottom of the clutch housing, although thankfully none on the clutch itself. Oil levels in both gearbox and engine were respectable enough so that doesn't really help with saying where the oil has leaked from. Replacing the gearbox seal is easy enough and I have a new seal lurking in the garage, but of course if it is the crankshaft seal that has failed then I'm looking at a great deal more work to get at it. Even getting the clutch off to take a peek is a PITA.
So is there a shortcut I can use to diagnose which seal has gone? Or shall I play by the rules that whatever I touched last is most likely to be duff and replace the gearbox seal and see what happens?