Learn a lesson on bad gas

If it is sticky... Its varnish.....

Pull the tank.... Back flush the fuel line.... Blow it out with air.... New filter... Take the carb apart and clean it out....
I was able to free all the valves in the one I did with WD40.... However this engine did not bend any valves, but it did bend a bunch of push rods.... pull the intake and flush it... as long as the guides are not 2 tight you can get them freed up, if you dont want to pull the head....
What happens is when the varnish cools it gets rock hard between the valve stem and the guide....

Good luck...