Originally Posted by Veter
Thank you, everyone! Rdwalker, pics were VERY helpful, saved me a lot of time. I checked plugs and throttle cables, they were OK. To be on the safe side, changed the air filter. Doing it found a problem that can be the reason of vibration and decrease in output
Moreover, there are some torn uneven edges on top of the engine, I wonder if it is normal
Hmmm... I cannot orient myself on those pictures. The first one, is it the rubber boot on the swingarm? If so, it is not very good for the driveshaft, but should not cause the problems you are experiencing.
The second picture is a mystery to me as well. Can you describe the location?