Could be a number of things. The best answer I guess would be to say a bad seal between two surfaces. Like a bad seal between the cylinder head and the actual cylinder due to an improperly torqued head gasket. A bad crank case seal on either the trans side or stator/flywheel side << they wear out over time and can dry up even. There is many reasons. the biggest thing is to find them and fix them. A 2 stroke motor needs to be air tight. Air leaks are detrimental.
Where you circled is a common air leak spot. Some yamabond or similar sealant will fix that up quick. Like I said before,,, every time you find a leak fix it and then look for the next. Unfortunately it is not uncommon for a new owner of a 2 stroke to find many air leaks. Most are fixed fairly easy and inexpensive. It just takes time to find them. Fix them now or be prepared to fork out some cash later.
Almost forgot,,, don't over tighten those bolts as you can warp the intake . that is if is already not warped.. Yamabond or alike sealant usually fixes that problem though. And or a new intake gasket.