Rear cylinder, again

[betmenas]

Hello, i have issues with rear cylinder, took the bike to the service, but they cant fix in 3 times...main problem a little bit wet spark plug, after i change it, rear cylinder starts to work, but with weird sound, also there is smoke from the exhaust...any ideas? Is it wrong syncro? Valves? Piston rings? The mechanic has adjusted the valves and cleand carbs, but i dont trust him anymore there is the video with the sound from the exhaust.

[WintrSol]

Did your mechanic check the fuel level in the carb? Have you checked the air cleaner under the seat?
Hard to tell what's making that hammering sound, but was the compression checked?