ES2 Engine problems

I'm looking for some inspiration/guidance!

I have two problems with my engine 55 ES2, one is oil getting into the combustion chamber and the other is a noise a bit reminiscent of a high mileage Ford pinto engine!

The bottom end was allegedly rebuilt before the bike was put away in the 90s, it has since had a rebore and was fitted with modded 16h piston. It has smoked excessively, esp when cold, since I bought it and got it going - compression is good and it runs without a head gasket, on removing the head there was oil on the top of the piston, about half a teaspoon. There was also oil in the ports. The head has since away to mike P, and has new valves guides, valve seats and springs etc. There is no longer any oil in the intake port but there still is on the piston. I was unsure about the piston so have just fitted a new Gandini piston, all in spec, and I was hopeful that this would solve the problem but alas no, it smokes as much as ever! Primary and mag chains are adjusted properly.

I thought the oil might be because of wet sumping, but I tried draining the sump before starting and that made no difference either.

Which brings me on to the noise, this seems to be at the top end but it's difficult to say. When I removed the 16h piston to my concern I could see that it had been just hitting the head because the chamfer on the piston crown was too small. There is no evidence of the new piston hitting but the noise is still there. I've checked the push rods, they are ok. And nothing is lose. My disadvantage is that I don't know how noisy these engines are normally, mine is certainly lovely and quiet when cold, it takes about a minute for the noise to appear.

i can only think big end/Rod damage as a result of the piston touching the head but it seems to be higher than that. Do the cam bushes or followers suffer wear on these engines?

any thoughts?