Thanks klx678. Glad I've read your post. Today for the first time I measured the chain slack using the standard procedure as per the manual. Only 2 cm instead of the recommended 3,5 - 4,5. Adjusted it to around 4 cm. I guess it was too tight since the first day I bought the bike. The local mechanics here are obviously not too smart.
I ride 99% street so chain doesn't get too dirty. Always use motor oil as chain lube which I apply with a brush. Some of the oil flies off and takes some dirt/dust with it. My feeling is that chains last longer than using regular chain lube. Also the o-rings are keep moist this way.
Will revert re chain noise after some driving today.

 

Adjusting for proper chain slack did not reduce the noise. The culprit is apparently the minimalistic front sprocket cover. Need to modify it