I like simple first.
Pull and clean or replace spark plugs. Spark plugs tell you a story, no doubt.
Next, empty the gas tank, fill it with good fresh gas from a place that moves a lot of fuel (Fresher), pour in a full can of seafoam, and run that tank of gas thru it including some wide open throttle once it's warmed up. The two strokes need wound up from time to time, once warmed up. I always do mine that way at least one good stretch EVERY TIME I take it out. Around here, one of the worst abuses I see are two strokes that are too small for the job on pontoon boats that just putt around just above idle, and to add more misery, the owners put too much oil in the gas tank. Makes for a gummed up, messed up motor. "Blow the soot out" my late Dad would say.
If these couple of things don't fix the issue, it's a cheep try, and gives you a good base line to move forward. I would want these bases covered before going too far advanced into it.
Going forward, I recommend using a good fuel treatment in every tank full of fuel, especially if it's not getting run fairly regular.
Cheap insurance. Most are just one ounce to 10 gallons of fuel, that's not going to hurt.
Oh, and keep check on fuel hoses! The older hoses can start breaking down inside, and send trash on down the line. The newer style hoses have an inner liner to help prevent that, or postpone it. Some cleaners ran thru deteriorated hoses can make things worse!
Good luck!