smoke from oil tank & breather

More likely to be worn rings, the bore last for at least 2 sets of rings before a re-bore is needed. Do a leak down test to find out where the leak is or just put some oil in the spark plug holes and see if the compression increases as you kick due to the ring gaps being temporarily blocked by the oil.

Other clues which may not be present but could be.

If its rings then the bike should be smoking from the exhaust under acceleration, if its the inlet valve seals them the smoke will be on the overrun/engine braking.

Another test for the inlet seals is to block the oil feed to the head and run the bike, if the smoking at the breather stops then its more likely the inlet valve seals.

Sounds possibly like rings then but a bit odd to be both sides and the figures are not bad, the driveside normally wears more as less oil gets to that side. That was the side pumping out blue smoke on mine on acceleration before new rings restored clean exhaust gases. What colour is the smoke, its not that unusual to see steam coming out the breather as with every gallon of petrol burnt nearly a gallon of water is produced and some does get past the rings into the cases. I would want to see more symptoms before tearing into the motor.

Most probably just very fine emulsified oil mist making its way up the breather. Ride the bike for a good 30 miles and then check, I suspect it will have cleared by then. 

Good call, Ashley...No-one has asked either when the oil was last changed. When I was seriously riding mine, it had 4 or 5 changes per year. Sometimes once a month.

"Needs some stick to get it warm!"- Just came across my old Ogri book, and that's a quote from Ernie Thrasher, road-tester for Loonycycle Magazine.....