Hi Big T,

I just rebuild my engine recently, bearing, cam chain+ piston ring after 55000km
Had a bad oil leak towards what I thought was the cylinder gasket, so opened the engine again change the gasket...
The leaks remained, then I thought it was the clutch cover gasket ...
Eventually a friend came along and within 5 minutes saw that the leak was actually coming from the other side of the engine..
I forgot to put back one small screw...
If only I took the time to really check the leaks I wouldn't have waisted this time searching and fixing the wrong part...

From my view if there is smoke there is probably some oil left in the cylinder head
So I think one possibility would be that the piston ring don't do their work properly, as it can be tricky to put them back.
So I was thinking maybe you did not adjust each ring with the right angle allowing the oil to filter through.Especially if your bike has a certain mileage the cylinder get used irregularly on its surface.
For the noise I experienced also a noise after the rebuild, I found that I adjusted the timing chain correctly but then did not use the right torque and the bolts were getting lose...
The lesson I learnt is that those engine are quite basic so if something does not run properly it probably comes from one own inexperience and mistakes...

Hope my modest experience will help...