The two cylinders appearance suggests to me that it is burning oil more on the lhs than the right?
Maybe there is one duff valve guide seal or a cracked/worn guide...............will strip the head and investigate.
A different (modified) head is waiting to go on but it's nice to understand where the smoke is coming from.
Bores look OK to me.
Even plug colour is not bad despite oil burning.
Pains me that it costs me £55 a go for a head gasket plus another £50 for valve seals for the other head.
If I am keen enough I will measure CR by volume and skim the head a little if it's not already too high. Good to confirm JE claim of 11.5:1.
Not sure whether its best to have the barrels off and replace the base gasket? It's not a high pressure seal obviously and I feel it should be OK to re-use the old one. I am always fearful of breaking a ring when I refit the barrels especially with the motor in the frame. Any experience to the contrary here?