Hello Dear Community,
First I apologize in advance, my English is not good and I use the Google translation, to post my question,

Yesterday I bought myself a birthday present, T�n�r� 08 with 60K km on the clock,
I wanted this bike for years
I do not know the bike or its normal engine noise but I think its sound is not healthy,little more on the left side.

The engine works and responds well, today I replaced the air filter and oil filter and spark plug, at the same time I unscrewed the cover of the box on the right to check a common problem recommended by a friend to check, this nut that holds the gears near the clutch mechanism (picture attached),


I tried to find out if it is released, but it's not, it's very strong not loos so I closed the cover, and filled oil.

So after I moved the bike I noticed the noise more noticeable on the left (after that I saw on the right side everything is fine)


I would like to ask you, what are the common causes noise on the left side of the engine? What would you recommend that i check first?

Thank you very much in advance