Strange... Mine never did the 4 stroking thing... Its mostly the Italian and French peds that do that .. not the Jap stuff.
Try running with no air filter for a minute to see if the situation changes.
If it doesn't change.. then maybe you are not 4 stroking because of jetting.
It might be something else.. (or it might not be 4 stroking)
And I don't know if Honda sells a smaller jet.
If it truly was 4 stroking from rich jetting .. then a smaller jet would make you go faster.
And by the way... How fast does it go?