Noticed this yesterday.
Suspect drive or gear shaft but is the breather down there too?
Any suggestions much appreciated.

 

A little more info on the location.
Pics help immensely.

 

What breather?

 

down or up on left hand side? did you check the plug for looking at the timing mark? clean it up on that side and go ride a bit and see where it's coming from.

 

plug for looking at the timing mark?
Sorry don’t understand.

 

Take a picture, please.

 

Can take a pic but pretty sure it's coming from the drive shaft area. Got oil on the back tyre. Has happened about 250 miles into new chain and sprockets that I had fitted. Was told they had to use heat to undo the nut on the front one.
Could applying heat have damaged anything?