^ditto - there should not be any oil coming out the exhaust for any reason
the tappet cover o rings will leak if you adjust the valves, and the re-use a dried out stiff o ring
happened on my 650, was drizzling all the way down the engine by the output shaft and leaving drips of the floor - I thought it was the output shaft seal, throwing it all over the engine as it spins
till I washed the engine down good with Era laundry soap, started it up: tappet cover.
you may be able to get to the rear exhaust tappet cover without taking anything off the bike - you can on a 650. To get to the intake tappet covers you have to strip the bike all the way down to the carbs-off.