You had it sleeved, but are using the previous pistons? That's unusual, because sleeving is done when a barrel is worn out, after having already been rebored to take oversized pistons. Sleeving takes the bore back to standard, so your oversized pistons can't be used
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The sleeve at the bottom of the barrel was cracked thats why I had them sleeved they were not worn out and it was cheaper to have them bored out to +20 and keep the pistons (which appear fine) than what it was to buy new pistons
The rings are new but original hepolite and there is no indication of a top or bottom they only have a tiny chamfer both sides
The sleeve bore hone was done by a real BSA engineering expert so I doubt its that.
Oil straight 40 Morris cheap and cheerful
Unfortunately I dont take it that easy running in or not lol
Guides new 2 of the 4 oversize and reamed out and valve seats replaced in engineering shop.
The only thing left to suspect is that its not scavenging well enough so it looks like another £300 on an SRM oil pump
I have gone over head and barrels with a fine toothcomb looking for any sign whatsoever of crack and cant see any sign plus the fact I doubt that would cause it to smoke on both cylinders even if the left hand one is a bit worse than the right