The other day when I was in the garage moving around one of my other (inferior

The oil looks yellowy in colour, so I do not believe it to be 2T oil, so I suspect it to be gearbox oil. Anyone know where the gearbox oil breather is located, and if it could leak oil onto the rear tyre? Could the oil be from another source perhaps? The wheel rim itself seems clean, so I don't think the oil was from the silencer spanny connection (although there is a small leak from here on the right hand spanny).
This seems to be the one issue with an otherwise excellent bike and I'd love to get it out again when the weather is a bit warmer, so I just need to work out where this goop is coming from. Anybody got any ideas? I even thought it could be brake fluid, but the rear brake hose does not look to be split and the rear brake appears to work well.