[b52bombardier1]

Dirty carburetor or vacuum leak between the carb and intake manifold.

I will also bet the fuel has ethanol in it and is old. Not good in either case. You could also have a dirty fuel tank cap vent that traps a vacuum and stops fuel from leaving the tank.

Your valves also might be too tight. Basically, you need a no holds barred, Texas style, fight to the finish, by the book tuneup. Chasing gremlins before doing a tuneup is like rearranging the deck chairs on the Titanic.

A complete waste of time.

Rick

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[b52bombardier1]

I have used Denso on other bikes - worked OK. You need to watch that plug for changes to the color of the internal porcelain. Sooty, black like that first picture is pig rich! Way too much fuel or not enough air - how clean is your air filter? You want a nice, chocolate tan on the spark plug for Goldilocks bike operation . . . not too hot, not too cold, not too lean, not too rich . . . . just right.

Rick