It can be kind of hard to describe intricate fixes like this online. If all else fails, take the engine off the bike, and take it to a good lawnmower shop. I know this is considered the cop-out, non-enthusiast fix by many, but I seriously don't understand why more new or inexperienced people don't do this if it prevents them from further frustration or messing up their engine further.
A lot of mower shops won't touch a minibike or go kart (some will, it depends) b/c of certain liability issues, but they will gladly work on a engine mounted on a small wooden stand. And they'll even explain how they fixed the problem to you (if they're cool (or speak English)) so you can fix it yourself next time.
I used to do this myself and actually learned a lot talking to the mechanics more experienced than me in person, and having them point out to me how they fixed it right before me. I even learned one of the mechanics is a halfway active member here, and owns a lot of really cool bikes.